Patent Publication Number: US-7590746-B2

Title: Systems and methods of maintaining availability of requested network resources

Description:
FIELD OF THE INVENTION 
   The invention relates to a method of maintaining availability of requested network resources, a method of data storage management, a method of data storage management in a network, a network of resource servers, network, a resource management server, a content management server, a network of video servers, a video server and software for controlling the distribution of network resources. 
   BACKGROUND ART 
   The invention arose from a consideration of Internet Web Servers and it is convenient to discuss it in that context, but the invention has wider applicability to other networks. Current web server systems, for example e-commerce systems, application servers or any other web accessible system, intended as web-servers for connection to the Internet typically comprise a web-tier, an application tier and a storage tier, see for example  FIG. 1 . The web-tier is typically highly replicated and homogeneous having a large number of web servers which have data and applications highly distributed over them in a homogenous manner: the servers all do the same thing. Each of these web-servers will serve the same data for a given service provider (e.g. xSP Internet, application or storage) in order to spread the accessibility of the data to thousands of users. The data content of each server in the web tier is therefore identical across all of the servers. This results in a massive utilisation of disc space, in which some of the data content is not heavily accessed. This leads to a large amount of often redundant storage: a lot of data content and application may be not be being served out at all frequently. 
   Load balancing (directing a specific request for a specific resource to be served out to a specific chosen sever on the web tier) can be used to attempt to provide a better, faster, service to users of the World Wide Web. For example “IP Virtual Server” software exists for Linux. Current web-based load balancing techniques for balancing the load between web tier servers are rudimentary and in one known version of load balancing involve a principal server, router, or director server, distributing requests for data to a series of identical data content servers sequentially in turn until a server capable of servicing the request is found. What the director server is looking for is a server with the processing power free to service the request for data. It does this by asking a series of servers in “Round-Robin” until it finds one capable. An alternative load-balancing technique for web tier servers is to have the director server (or router) send an investigatory signal to the web tier servers and assess which server had the quickest response time, and to direct the request to be serviced to the web tier data content server which replied fastest. This technique of measuring response time is primarily a measure of the telecommunications links to the web tier servers: the capacity of the telecoms links is the major factor in response time. Depending upon whether the data content web tier server has a dedicated IC (interface card) or not, the response time may be influenced slightly by how busy the CPU of the web tier server is, but telecoms factors far outweigh this usually. 
   Application servers (i.e. servers in a network serving to the network particular applications—often different applications on different networked servers) have a problem of scalability if demand for a particular application rises. Clustering is one answer to problems of providing greater access to data and functionality, but it is expensive to replicate data content and functionality, and it is difficult to expand the capacity of a cluster of services horizontally by the addition of more resources in real time whilst the system is operational. 
   Clusters are not easily scaled horizontally by the addition of more network attached storage (NAS) at the web-tier level. NAS typically does not scale well horizontally as it is attached via a network interface card (NIC) to the network and there is a limit on the number of network connections allowed by the NIC. A NIC has a capacity to handle a limited number of connections. Cards are typically rated at 10 Mbits −1 /100 Mbits −1 /1000 Mbits −1 . Clusters typically require the purchase of expensive, cluster certified disc arrays and fibre channel, to support shared data between clustered servers. 
   Clustered systems typically fall into either a ‘shared everything’ class: where fibre channel, storage and switches etc. are shared by the clustered machines, or a ‘shared nothing’ class: where each machine on the cluster has its own storage, fibre channel and switches etc. It is difficult to configure the cluster. The ‘shared nothing’ arrangement is very expensive with high end disc arrays costing around $300 k per TeraByte (TB), and also as each disc cluster will contain similar data content at each server, or node, the expenditure on storage, and other peripherals, rapidly escalates. 
   A further problem with current web tier servers is that it is difficult and expensive to add extra data. For example, in the field of Internet Video Serving (serving out video movies over the internet) a video website may have, say, ten web tier servers each having a copy of the one hundred most popular video films on them. A director server, or router, receives a request for a specific video and directs it to a chosen one of the ten servers either on the basis of “Round-Robin”, or by assessing telecoms response time. The chosen server serves out the selected video. However, let us imagine that a new video is to be added to the available videos. The new video is loaded into the memories of each of the ten web tier servers and added to the available videos deliverable in the directory of the director server. It will probably be necessary to delete a video from the available number of videos to make room in the memories of the web tier servers. 
   A lot of the memory of each web tier server is not actively used in any given period of time: a lot of it is redundant most of the time, but is needed in case there is a request for a less frequently requested video. 
   There are difficulties in horizontally scaling. Adding another web tier server means updating the director server and copying the data content of the other web tier servers to the new web tier server, so that they are the same. 
   If it is desired to increase the number of video titles available at that website it is necessary to increase the memory capacity (e.g. disc capacity) of each of the web tier servers so that they can accommodate more videos. 
   Currently collections of servers that deliver content, e.g. streaming of videos, to a user are unaware of their storage capacity, connection capacity and bandwidth usage. A central management tool, typically a management protocol such as simple network management protocol (SNMP), loaded on an overseer machine, can in known systems assume a wide scale, low level monitoring responsibility that will typically include tripping an alert on a monitoring station if a server, or other network element, fails or if network traffic exceeds a threshold value. An attendant problem with this arrangement is that at the time that an alert is registered it may be too late for a network administrator (person) to introduce a replacement server, or other additional network element, prior to a catastrophic system failure. Also, there may not be a network administrator present at all times to react to a warning message. 
   An example, the wide variations in demand for web-sites, for example an increased demand for information, or live video feed during major sporting events, has resulted in web-sites crashing as the systems administrator cannot establish the rate of change of requests quickly enough in order to add resources quickly enough to cope with the fluctuations in demand. A known solution to this problem is to massively over provide for the availability of data to users: to have much more data-serving capacity than is normally needed. This is expensive and inefficient as at times of low data demand it results in large amounts of storage devices lying idle. High end disc arrays typically cost $300 k per Tera Byte (TB). 
   It is possible to provide clusters of servers in order to accommodate fluctuations in demand for data. However, as mentioned, clusters typically require the purchase of expensive, cluster certified disc arrays and network infrastructure, typically fibre channel, to support shared data between network nodes. Additionally, clusters tend to be built in advance of demand and are not readily horizontally scaleable, for example by the addition of network attached storage (NAS) or by the addition of direct attached storage (DAS) to servers. 
   Video serving over the internet is currently not very popular because it is so expensive to do, for the reasons discussed. 
   SUMMARY OF THE INVENTION 
   According to a first aspect the invention comprises a method of satisfying a demand on a network for a network resource, the method comprising providing the network with a demand director server, a first resource server having a first resource thereon, and a second resource server having a second, different, resource thereon; and the method further comprising having said director server be aware of what resources are held on said first and second resource servers and upon receipt of a request for one of said first and second resources selecting one of said first and second resource servers to serve out said requested resource and directing said request to said selected one of said first and second resource servers, said demand server selecting an appropriate one of said first and second resource servers to receive said request using its knowledge of where the requested resource is located. 
   Previously in world-wide web-based networks there has been no differentiation in resources provided on web-tier servers: the data content and applications deliverable have been homogenous between web-tier resource servers. Furthermore, even in other, non-internet/world wide web environments, networked servers capable of serving out the same kind of resource (e.g. videos) have all had identical content: not different content per server. 
   In the above invention the demand director is aware of where different resources are stored so as to be able to direct a request for resources to the appropriate server that actually has the requested resource stored on it, but the demand director is not necessarily aware of the current demand/load on each resource server—but it might be. 
   According to another aspect the invention comprises a method of satisfying a demand on a network for a network resource, the method comprising providing the network with a demand director server, a first resource server having a first resource thereon, and a second resource server having a second resource thereon; and the method further comprises having said director server be aware of unused resource-serving capacity of said first resource server and of unused resource-serving capacity of said second resource-server, and said director server upon receipt of a request for a requested resource which is present on both said first resource server and said second resource server selecting a selected one of said first and second resource servers to be the resource server that serves said requested resource, said director server selecting said selected one of said resource servers using a knowledge of whether or not said first and second resource servers have unused resource-serving capacity capable of serving said requested resource. 
   In this aspect of the invention the director server is usage-aware (usage of the server, as well as or instead of telecommunications availability to the server), and the content, or resources, of the resource server may or may not be dissimilar. 
   According to a third aspect the invention comprises a method of sharing the demand for resources between a plurality of networked resource servers comprising providing dissimilar resource content on at least some different resource servers, having a knowledge of what resource is available for serving out from which of said networked resources servers, having a knowledge of said resource servers&#39; current capacity to satisfy a request for resources that they are capable of serving, and allocating a request for a requested resource to a selected resource server chosen with the knowledge that it has said requested resource available for serving and that it has the capacity to serve out said requested resource satisfactorily. 
   This aspect of the invention combines the first and second aspects. 
   The director unit may also comprise a resource server (e.g. it may also serve out resources such as videos). The data may be rich media files, which typically include real time (RT) video and/or audio files and/or MPEG files, and/or Real Networks format video data or Windows Media format data or any other file based format. 
   Each resource server may store dissimilar data content thereupon. By dissimilar we mean either (i) that the data, or resources, accessible by an external user is not directly mirrored and completely replicated across all of the resource servers units (whereas the operating system, etc. can be the same for all of the resource servers); or (ii) that the data, or resources, accessible by an external user is very substantially different between at least some of the resource servers; or (iii) that the data, or resources, externally accessible by a user is wholly different, or nearly so, between at least some of the resource servers, or (iv) that there is a great deal of data content, or resource, difference between different resource servers some of which may or may not have any shared, common, deliverable-to-the-user resource. At one extreme each resource server could have entirely different, or nearly so, resource content—but it is not intended to avoid this patent simply by duplicating some content between some or all resource servers. 
   The director server may have a database therein which may detail which resource server has any given resource thereupon and may detail any one, or combination of the following for any given resource: access figures, statistics, metrics on utilisation, number of clients, or users, currently accessing the data, time periods of frequent access number of clients, or users, historically served. 
   The resource servers may have data storage units associated therewith. The data storage units will typically be disc arrays but may include tape drives. The data storage units may be internal of the resource servers and/or they may be external of resource servers, for example network attached storage (NAS). 
   The director server may be arranged to load balance data access and/or the distribution of data across the server network, or across a server farm. The concept of moving data, or resources, around the network automatically to improve network performance is interesting and novel. 
   A request may be serviced by whichever resource server is adjudged to be the most able to serve out said requested resource. This concept of being aware of capability capacity to serve out, and making decisions relating to resource management and availability based upon such knowledge constitutes a separate invention. 
   A requested selected resource server may serve up a reply to a request for resource in such a way that said reply appears to a requester who made said request to be coming from said demand director. The demand director server may be arranged to forward a packet of a request to a chosen resource server The chosen resource server re-writes the packed header. The resource server may have first and second network interface cards (NIC&#39;S). The second NIC may be configured to enable communications with an external network. The demand director server may have an interface, which may be arranged to specify input/output ports for an application and/or resource servers. The first NIC may be configured to enable intra-farm, or intra-network communication, typically with the demand director server. Having two subnets serves to restrict communications with outside users and movement of data within the farm or network to alter its availability to serve: thus one subnet may exist for each function so as not to congest either subnet. 
   The resource server may be arranged to rewrite the packet headers of outgoing data such that they appear to be transmitted from the demand director server. This will typically involve writing a network address of the director unit, usually a transmission control protocol/internet protocol (TCP/IP) address, with the packet header. 
   The director may provide an ephemeral means to access the data e.g. via the use of a file systems symbolic link which is typically time limited and is removed after the expiry of a pre-determined length of time, usually after a client, or user, has already started accessing resources (e.g. content). The removal of the symbolic link does not typically alter the client&#39;s consumption of the data but will usually prevent reaccess of the data without requesting a new session through the director. 
   The demand director server may be arranged to configure and/or start and/or stop resources (or applications) upon the resource servers and/or add, and/or remove, at least one resource server from the network, or farm, in response to variations in the number of requests for data. Alternatively, the director unit may be arranged to recommend to an administrator (e.g. a person) the addition/removal of at least one resource server to/from the farm (or network) in response to variations in the number of requests for resources. The demand director server may be arranged to distribute data over the resource servers of the network/web tier/farm. 
   A copied resource may be created by copying resource from a said resource server onto another said resource 
   server, and having said demand director be aware that said copied resource exists on said another resource server. The copying of said copied resource may increase the availability of said copied resource available for serving out from said resource servers. Resource may be deleted from a selected resource server, thereby freeing-up resource server capabilities for use to serve up a different resource. It is in some embodiments desirable to dynamically distribute servable resources between available resource servers dependent upon demand for said resources, and to vary the capacity of said resource servers collectively to serve out demand for a particular resource dependent upon the demand for said particular resource. The demand director server may be capable of communicating with an additional resource server that previously was not making its resources available for serving requests received by said demand director server, and of arranging for said additional resource server to make its resources available for serving requests received by said demand director server. 
   In some embodiments the invention provides horizontally scaleable, distributed data storage arranged to be connected to a network, typically for use with audio or video data. 
   The concept of copying, or migrating, data dynamically to expand overall network capacity to serve out a particular kind of resource can apply to the prior art arrangements where all web tier servers have the same content/resources. It is still possible to add a server (with the same content) to the network in response to demand. It is still possible to increase the capacity of all servers together to serve out a specific resource that is in demand (e.g. a further copy of the most popular movie could be added to each content server in response to demand, possibly at the expense of over-writing a copy of a less popular movie. It is not absolutely essential to use different, asymmetrically distributed, resources/content to use the “migration/copying of content” invention. 
   There may be more than one demand director server. This increases fault tolerance. 
   According to another aspect of the present invention there is provided a demand director server comprising a processor and a data storage device, the demand director server being arranged to manage asymmetric distribution of data across a plurality of data storage devices and mediate requests for access to said data so as to load balance the requests for data received by each of the data storage devices. 
   The demand director may copy data to different memory locations itself, or it may initiate a data copying process that is actually performed by another machine. The management of the data across the plurality of storage devices improves the efficiency of data storage. The load balancing of the requests for data improves the efficiency of usage of the storage devices and aims to ensure a high degree of reliability to the supply of the files to a user. 
   The processor may be arranged to facilitate the uploading of data from tape media, a DVD or audio CD to the storage devices. Alternatively, the processor may be arranged to facilitate the downloading of data from a network, typically the Internet. 
   The processor may be arranged to update a data (or resource, or content) location database, for example whenever any one, or more, of the following occurs: the number of storage devices is increased or decreased, data is copied to or deleted from a storage device, data is uploaded, or downloaded, to a storage device, an application, or resource, resident upon a data storage device is started up or shut down. 
   The demand director server may be arranged to act as a Level 7 switch. High level network switches are aware of the types of request being made within a data packet and can deal with the contents of the packet dependent upon the type of request. Level 7 switches are described in the Open Systems Level model of network information systems. 
   According to another aspect of the present invention there is provided a method of data storage management of data in a network comprising the steps of:
     (i) monitoring the usage of a servable resource;   (ii) determining if the usage of said resource has increased or decreased;   (iiia) introducing an additional resourcer server to the network and/or starting up a resource-serving application on a resource server if the usage has increased; and/or   (iiib) removing said resource from a resource server and/or shutting down a resource-serving application on a resource server if the usage has decreased.   

   In many embodiments, especially those with asymmetrically distributed resources/content over the resource servers, the method will also update a database containing details of which resource servers have which particular resources thereupon. 
   The method may include removing a resource server from the network as part of step (iiib). The method may include copying a resource to the additional resource server as part of step (iiia). The resource may be a data file, such as a video. 
   According to a fourth aspect the invention comprises a server network comprising a demand director server, a first resource server having a first resource on it, and a second resource server having a second resource on it, different from said first resource, said director server being aware of where said first and second resources are located, and being capable of receiving a request for a selected one of said first or second resource to be served out, and of directing said request to whichever said resource server is determined to have said requested resource. 
   The request may originate from outside of said network, and the resource may be served out of said network. 
   According to another aspect the invention comprises a server network comprising a demand director server, a first resourcer server having a first resource thereon, and a second resource server having a second resource thereon; said demand director server being adapted to be aware of unused resource-serving capacity of said first resource server and of said second resource server, and said director server being capable, upon receipt of a demand for a requested resource that is present on both said first and said second resource servers, of selecting a selected one of said first or second resource servers to serve out said requested resource and causing said selected one of said first or second resource servers to serve out said requested resource, said demand director being adapted to use a knowledge of said unused resource-serving capacities for said selected resource of said first and second resource servers when selecting which resource server is to be said selected resource server and serve out said selected resource. 
   According to another aspect the invention comprises a demand director server adapted for use with a plurality of resource-serving resource servers having resources distributed between them, said demand director being capable of monitoring and managing distribution of resources across said resource servers, and of mediating requests for resources to be served out by said resource servers so as to direct a request for resource-serving to a chosen resource server chosen by said demand director using a knowledge of which resource servers are capable of serving out the requested resource. 
   According to another aspect the invention comprises a method of network resource management comprising, in a network having a demand director and resource serving servers, the steps of:
     (i) receiving at a demand director unit a request for a resource from a requester;   (ii) determining the availability of resource serving servers that are capable of serving said requested resource;   (iii) selecting a resource server that is capable of serving said requested resource and sending said request to the selected resource server;   (iv) establishing a connection between said requester and said selected resource server;   (v) serving out said selected resource from said selected resource server to said requester.   

   According to another aspect the invention comprises a method of satisfying a demand on an Internet network for a network resource, the method comprising providing the network with a demand director server, a first resource server having a first resource comprising one of a video file and a data file thereon, and a second resource server having a second, different, resource comprising one of a video file and a data file thereon; and the method further comprising having said director server be aware of what resources are held on said first and second resource servers and upon receipt of a request for one of said first and second resources selecting one of said first and second resource servers to serve out said requested resource and directing said request to said selected one of said first and second resource servers, said demand server selecting an appropriate one of said first and second resource servers to receive said request using its knowledge of where the requested resource is located. 
   According to another aspect the invention comprises a method of satisfying a demand on an Internet network for a network resource, the method comprising providing the network with a demand director server, a first resource server having a first resource comprising one of a video file and a data file thereon, and a second resource server having a second resource comprising one of a video file and a data file thereon; and the method further comprising having said director server be aware of unused resource-serving capacity of said first resource server and of unused resource-serving capacity of said second resource-server, and said director server upon receipt of a request for a requested resource which is present on both said first resource server and said second resource server selecting a selected one of said first and second resource servers to be the resource server that serves said requested resource, said director server selecting said selected one of said resource servers using a knowledge of whether or not said first and second resource servers have unused resource-serving capacity capable of serving said requested resource. 
   Whilst envisaged primarily for use with video files, the invention can be used with other files (termed “data files” for convenience). 
   In one embodiment the invention comprises a web tier of resource serving servers comprising a plurality of resource servers at least some of which have different servable resource content, thereby enabling a specific resource to be served out of one resource server but not another. 
   In a further embodiment the invention may comprise a tier of resource serving servers comprising a plurality of resource servers at least some of which have different servable resource content of the same kind or class, thereby enabling a specific resource of a kind or class to be served out of one resource server but not another, both resource servers having resources of said some kind or class. 
   There is usually also a demand director server which is aware of which resources are servable out of which resource servers, and which is capable of receiving a request for a particular resource and directing said request to a resource server capable of satisfying said request. 
   The demand director may be thought of as part of the resource-serving web tier, or as sitting above the resource serving web tier as a demand director server/router: i.e. a level 7 switch. 
   According to an aspect of the present invention there is provided a network having a plurality of networked resource servers having dissimilar resource content, and a demand director, said demand director being aware of what resources are potentially available on which of said resource servers, and being capable of determining current capacity of each of said resource servers to serve out each of said resources that they are capable of serving out, said demand director being adapted to allocate a request for a specific resource to a resource server that it selects using its knowledge of what servers, and their capacity to serve out said requested resource. 
   According to an aspect of the prevent invention there is provided a demand director for use in a network of resource servers, said demand director having information associating specific resources available for serving out from specific resource servers, and being adapted to ascertain the capability of said resource servers to serve out their potentially servable resources, and being adapted to allocate a demand for a specific resource to a selected resource server using said information and said capability. 
   According to another aspect of the present invention there is provided a demand director for use in a network of resource servers having resources that are potentially servable-out, said demand director having the capability of ascertaining the capability of said resource servers to serve out their potentially servable-out resources and of using a knowledge of the capability of said resource servers to serve out a specific resource in determining to which resource server a request for said specific resource is directed. 
   According to an aspect of the present invention there is provided a network having a plurality of content servers capable of serving out con tent of a particular kind stored upon them, and demand manager means adapted to allocate a request for specific content to an appropriate content server for serving said request, said content servers having dissimilar servable content of said particular kind stored upon themselves and said demand manager means having mapping means mapping specific content with specific content servers such that said demand manager is adapted to receive a request for specific content and to allocate said request to an appropriate content server having said specific content upon it, using said mapping means. 
   According to an aspect of the present invention there is provided a network having a plurality of content servers capable of serving out content of a particular kind, and content server monitor means adapted to monitor capacity of said content servers to serve out specific resources, said content server monitor being adapted to allocate a request for requested specific content to a content server chosen by said content server monitor means using a knowledge of said capacity of each of said content servers to serve out said requested specific content. 
   According to an aspect of the present invention there is provided a metropolitan area video serving network comprising a plurality of video servers having at least some different videos on at least some of said video servers, and a demand director having a location map correlating the address of which of said video servers has which of said videos available for serving, said demand director being adapted to direct demands for a specific video to an appropriate said video server for serving out said specific said video, using said location map to select said appropriate video server. 
   According to an aspect of the present invention there is provided a metropolitan area video serving network comprising a plurality of video servers having videos available for serving out, and a video server monitor and demand director adapted to establish the capacity of said video servers to serve out additional videos, beyond their current activity, and to direct a request for a specific video to a video server that said video server monitor and demand director has established has said particular video and is capable of serving out said video satisfactorily. 
   According to an aspect of the present invention there is provided a method of satisfying a demand on a network for a network resource, the method comprising providing the network with a demand director server, a first resource server having a first resource thereon, and a second resource server having a second, different, resource thereon; and the method further comprising having said director server be aware of what resources are held on said first and second resource servers and upon receipt of a request for one of said first and second resources selecting one of said first and second resource servers to serve out said requested resource and directing said request to said selected one of said first and second resource servers, said demand server selecting an appropriate one of said first and second resource servers to receive said request using its knowledge of where the requested resource is located, and further comprising dynamically distributing servable resources between available resource servers dependent upon demand for said resources, and varying the capacity of said resource servers collectively to serve out demand for a particular resource dependent upon the demand for said particular resource. 
   According to an aspect of the present invention there is provided a method of satisfying a demand on a network for a network resource, the method comprising providing the network with a demand director server, a first resource server having a first resource thereon, and a second resource server having a second resource thereon; and the method further comprising having said director server be aware of unused resource-serving capacity of said first resource server and of unused resource-serving capacity of said second resource-server, and said director server upon receipt of a request for a requested resource which is present on both said first resource server and said second resource server selecting a selected one of said first and second resource servers to be the resource server that serves said requested resource, said director server selecting said selected one of said resource servers using a knowledge of whether or not said first and second resource servers have unused resource-serving capacity capable of serving said requested resource, and further comprising dynamically distributing servable resources between available resource servers dependent upon demand for said resources, and varying the capacity of said resource servers collectively to serve out demand for a particular resource dependent upon the demand for said particular resource. 
   According to an aspect of the present invention there is provided a method of sharing the demand for resources between a plurality of networked resource servers comprising providing dissimilar resource content on at least some different resource servers, having a knowledge of what resource is available for serving out from which of said networked resources servers, having a knowledge of said resource servers&#39; current capacity to satisfy a request for resources that they are capable of serving, and allocating a request for a requested resource to a selected resource server chosen with the knowledge that it has said requested resource available for serving and that it has the capacity to serve out said requested resource satisfactorily, and further comprising dynamically distributing servable resources between available resource servers dependent upon demand for said resources, and varying the capacity of said resource servers collectively to serve out demand for a particular resource dependent upon the demand for said particular resource. 
   According to an aspect of the present invention there is provided a computer readable memory device encoded with a data structure for managing networked resources held on a plurality of resource servers connected to a network, the resource servers having a plurality of server programs running thereupon; in respect to a change in network traffic the data structure having entries, each entry containing:
         a network address associated with a resource that is servable out; and   resource server-utilisation information or statistics.       

   According to an aspect of the present invention there is provided a method of making available computer network resources to users of a network comprising having a plurality of resource servers capable of serving out a resource of a common kind, monitoring the demand for a particular resource of said common kind automatically using a computer, and modifying overall capacity of said network to serve out said particular resource automatically in response to monitored or predicted demand. 
   According to an aspect of the present invention there is provided a data structure for managing the automatic transfer of data between a server program and a further server program in response to a change in traffic on a network, said data structure being arranged to manage the distribution of the data over said server program and said further server program, said data structure having entries, each entry containing:
         a locator associated with said server program;   an identifier associated with at least a portion of said data; and   traffic statistics associated with network traffic to said server program.       

   According to an aspect of the present invention there is profided software for controlling allocation of a request for a specific resource on a network of resource servers to a selected resource server, the software comprising a director adapted to direct said request to said selected resource server, said director being adapted to receive a map input derived from a resource locator map adapted to provide network addresses at which specific resources are available for serving out, and said director being adapted to use said input to select an appropriate resource server that has said specific resource available on it for serving out and to direct said request to said appropriate resource server. 
   According to an aspect of the present invention there is profided software for controlling allocation of a request for a specific resource on a network of resource servers to a selected resource server, said software comprising a director adapted to direct said request to said selected resource server, said director being adapted to receive a capacity input derived from an evaluation of capacities of each of said resource servers to serve out said specific resource, and said director being adapted to select said selected resource server using said capacity input to establish that said selected resource server has capacity to serve out said requested specific resource. 
   According to another aspect the invention comprises a method of increasing the number of different resources servable out from a web tier comprising having a web tier in accordance with the previous aspect of the invention and adding an additional resource server to said web tier, said additional resource server having additional resources not previously servable by said web tier. 
   A resource server&#39;s capacity to serve out a resource that it has may be dependent upon:
         whether there is unused application software capable of serving out the requested search;   the amount of unused CPU processing power there is available;   the bandwidth available for serving out that resource from the resource server (which may be dependent upon which part, or parts, of the server can support the serving out of the requested resource).       

   The demand director may use information relating to one or more (or any combination of) the above in order to select which resource server will be chosen to serve out a demanded resource. 
   Information on what activity a resource serve is currently performing, and possibly when it expects to be freed of that burden, is useful to the demand director to enable it to evaluate the unused capacity of the resource server available to serve out additional resources. An alternative to having the demand director evaluate the unused capacity of a resource server to serve out additional resources is for the resource server to evaluate that itself and inform the demand director of its unused capacity (instead of its used capacity). 
   Preferably network traffic associated with each resource server is monitored by the demand director. Preferably the demand director has traffic capacity limits for each type of resource available on each resource director and uses these limits, along with a knowledge of current traffic for each resource server, to select which resource server will satisfy a particular demand for resources. 
   The method may include polling a resource server (or non-master server) by the demand director (or master server). The method may include replying to the polling, by the resource server with information relating to any one or combination of the following: network address associated with the resource server, bandwidth utilisation of the resource server, resource served out by the resource server (either/or, or both, currently and since the last polling), a network address to which the resource is being/has been sent, a price associated with the resource served. 
   The method may include generating billing information for a user by the demand director server. The method may include checking to see whether a bill is due, by the demand director server. The method may include billing the user. 
   The demand director may evaluate whether usage and/or network capacity information is within a predetermined limit. It may be determined whether a sever or server farm has spare data serving capacity and may include copying a file thereto. A demand director resource-location directory or database may be updated, typically with the network address of the resource server with spare data serving capacity, and an identifier associated with what resource is available for serving. 
   A further server may be connected to the network by the demand director, which may communicate, e.g. multicast, details of the new resource available and/or available bandwidth over the network. The method may include the storing of said details upon the demand director, or master, server and/or some or all other servers. The method may include directing a request for the resource content of the further server to the further server by the demand director server. The method may include varying the resource (e.g. data) content of the further resource server or by the demand director server dependent upon demand for said resource content. 
   The method may include self-monitoring of the bandwidth utilisation of a resource server and may include determining if the bandwidth utilisation of the resource server is within a predetermined limit. The method may include passing an alarm message from the resource server to the master server, demand director, if the bandwidth utilisation is outside of the predetermined limit. The self-monitoring of a resource server/content server may constitute a separate invention, not necessarily linked with the previous invention(s). 
   The method may include self-monitoring of an input-output (IO) port traffic by a resource server. The method may include transmitting the results of the monitoring to the demand director, master server. The results of the monitoring may be compared to a statistical model, and it may be determined if additional resource serving servers need to be connected to the network, by the demand director, master, server. The method may include connecting an additional resource serving resource server to the network. 
   The method may include having a server farm (a “farm” is defined later) and designating one of the servers of the server farm as a master, or demand director, server. The method may include storing on the master, or demand director, server a database containing details of any one, or combination, of the following: a list of federated server farms and the network address of the demand director and/or resource servers participating therein, resources potentially available on each server, network address of each resource server, current and/or historical usage statistics relating to each resource that can be served out, current network traffic through an input-output (IO) device of each resource server, the cost of accessing each resource, an identifier of users who have accessed any given resource. 
   The method may include setting a threshold level of network traffic through each (IO) device. The setting of a threshold means that problems such as when the network, or an individual server, is approaching its capacity can be determined early and extra resources or processing capacity added before the situation becomes critical. Typically, the IO device is a network interface card (NIC) or it may be an IO port, possibly of an NIC. The extra resources or processing capacity may be added automatically by the demand director without human intervention, or human intervention may be necessary. 
   The method may include resource servers informing the master server, or demand director, when the threshold level is passed. The method may include using the demand director&#39;s (or master server&#39;s) database to determine if there is an additional resource serving resource available within the network, or server farm, able to service a request for the resource being served by the IO device. 
   The method may include generating a bill based upon a user&#39;s aggregate access of resources. The method may include providing a central register of resources (e.g. data content) on a server farm, or farms. This allows digital rights management to be centrally tracked thereby limiting the opportunities for piracy. 
   According to another aspect of the present invention there is provided a computer readable memory device encoded with a data structure for managing networked resources held on a plurality of resource servers connected to a network, the resource servers having a plurality of server programs running thereupon; in respect to a change in network traffic the data structure having entries, each entry containing:
         a network address associated with at least one server resource program;   an identifier associated with a resource that is servable out;   resource server-utilisation information or statistics.       

   The utilisation information or statistics may be associated with network traffic through an input-output (IO) device associated with the resource servers. 
   The data structure may be arranged to facilitate the addition of further entries relating to an additional resource server, those entries containing one or more of: an additional network address, identifier and resource-server utilisation statistics thereto. The resource server-utilisation statistics entries in the data structure may include entries relating to any one, or combination, of the following: usage of resources, access patterns for the resources, access times for the resources, outgoing bit rates. The data structure may be arranged to facilitate a deletion of an existing entry therefrom. The data structure may contain an entry containing a port identifier associated with each resource. The port identifier may be a subset of the network address entry. 
   The data structure may contain an entry relating to a threshold level of network traffic associated with a particular resource on a particular resource server. The data structure may contain entries relating to upper and lower threshold levels of network traffic for particular resources on particular resource servers. Typically, these threshold levels will be expressed as a ratio of the theoretical to actual deliverable capacity of an input-output (IO) device, typically a network interface card (NIC). 
   Another thing that it is possible to do when there is a tier or network of servers with different resources (e.g. data content) of the same kind on them or associated with them, for example different videos, is to modify the capacity of the network to serve out a specific resource by replicating the resource and making it available from different, or more, servers on the network, or from different, or more ports on a server. This may make available different telecommunications bandwidth/routes, as well as increasing the overall capacity of processing power capable of serving out the specific resource. The original resource may still be present and functional on its original server, or it may be removed therefrom during the migration of data/resource operation. Thus, typically (but not always) in response to an increased demand for a particular resource (e.g. a specific video) the resource may be made more available on the network. Since the demand director allocates request for a specific resource to a selected one of those servers capable of serving out the selected resource, it will be usual to update the demand director&#39;s load balancing data to associate the addresses and capabilities of the server(s), or ports, to which the specific resource has been migrated, or copied, to the places at which the specific resource can be found on the network—so that the demand director can take into account the fact that it has an increased range of options post-resource-migration. 
   According to another aspect the invention comprises a method of making available computer network resources to users of a network comprising having a plurality of resource servers capable of serving out a resource of a common kind, monitoring the demand for a particular resource of said common kind automatically using a computer, and modifying overall capacity of said network to serve out said particular resource automatically in response to monitored or predicted demand. 
   Preferably, the method comprises having a demand monitor server monitor the demand for particular resources of said common kind, said demand monitor being aware of the capacity of each of said resource servers to serve out additional servings, beyond a current level of resource serving, of said particular resources. The demand monitor may be aware of the capacity of each of said resource servers to serve out additional servings of each of a plurality of user-selectable resources potentially available for serving out from each of said resource servers. The demand monitor may also comprise a resource server. 
   Thus, the demand monitor is “others aware”—it knows the capabilities of other servers (and of itself) to satisfy future requests for the serving out of each of different selectable resources of said same kind (e.g. different video movies). 
   The demand monitor may automatically cause additional capacity to serve out a specific resource to be created on said network, probably in response to monitored demand for said specific resource. However, said additional capacity may be created in advance of actual demand for it—in response to predicted future demand. The demand monitor may remove from said network capacity to serve out a specific resource, possibly to free-up serving capacity for a more popular resource. 
   The demand monitor may itself monitor what resources are being served out by what resource servers, possibly by monitoring traffic on input/output ports of other servers, or a resource server may monitor its own resource-serving activities and provide information to said demand monitor regarding what it is serving and/or its capacity to serve out additional resources, preferably information indicative of its ability to serve out each specific resource of said common kind available on it for serving out. 
   According to another aspect the invention comprises a method of monitoring network traffic on a computer network comprising having a network of computers, or servers, and enabling the individual computers or servers to monitor their telecommunication activity on their input/output ports and report on their telecommunication activity to a network traffic monitor. 
   Thus resource, or content, servers may self-monitor their network activities and/or their capability to contribute further to serving out particular resources. 
   The network traffic monitor may take an action automatically if network traffic for a computer or server is determined to be outside of permissible parameters. For example, if network traffic to a computer drops to too low a level an automatic alarm may be raised. Alternatively, or additionally, resources potentially available for serving from the computer/sever with a reported drop in telecommunications activity may be automatically made available for serving from one or more other servers in the network. For example such “missing” resources may be made available by automatically migrating content/resources from the server that is experiencing a drop in serving-out abilities, or by obtaining the “missing” resources from other places in the network (a record of what resources are available on what servers is typically kept on a demand director server). If the resources are kept on at least two different servers then a back-up copy should be available to be the “seed” for copying to a new server, to compensate for the degradation in service from the “missing”, or impaired server. 
   According to another aspect the invention comprises a network comprising a plurality of content servers and a monitor server, said monitor server being capable of monitoring the network traffic to and/or from each content server, wherein said monitor server compares monitored network traffic to a threshold level and upon traffic levels meeting said threshold level said monitor server is adapted to take an action. 
   Said action may be to increase the capability of the network to serve out content that is in demand. 
   Said threshold may comprise a level of capability of serving out content from a particular content server, and wherein upon a monitored level of content serving reaching said threshold level, said monitor server takes said predetermined action which comprises causing the capability of said network to serve out said content to increase. Said monitor server may be adapted to copy said content to another networked server. Said servers may have telecommunication ports and said monitor server may cause there to be an increase in the number of telecommunication ports made available to a particular content of a content server. Said threshold level may comprise a minimum activity threshold level and wherein said action comprises performing a diagnostic check to ensure that said content servers are properly operational and/or communicated with said monitor server. Said minimum threshold level may be assessed in many different ways, for example, a threshold for a particular resource, a threshold for overall network traffic to a specific server, a threshold for all resources from a particular port, a threshold for a specified resource from a particular port, or any other identified subset of measurable activity of said servers. 
   According to another aspect the invention comprises a server having a processor, a memory, and a self-monitoring software program capable of being run by the processor, said monitoring program when run monitoring levels of usage on applications servable out of said server and being capable of identifying when the level of usage of said applications reach a threshold level and in response thereto causing said server to take an action which increases availability of said application to a requestor who may request said application to be served to them. 
   Said action may comprise copying said application to another server. 
   When said server has a plurality of output ports and said application is available on less than all of said output ports, said action may comprise increasing the number of output ports of said server that are capable of serving out said application. 
   According to the present invention there is provided a data content server comprising a processor, a storage device and an input-output (IO) device (IO), the storage device having data content stored thereupon and the processor being arranged to execute a monitor application that is stored upon the storage device, the processor being further arranged to monitor the IO device when running the monitor application and to automatically determine whether a trigger condition has been met, and if so automatically to produce a control signal responsive thereto. 
   Said control signal may comprise a replicate signal adapted to cause at least part of the data content of the data content server to be copied to a further server or made available at a further IO port on said server. 
   This arrangement allows the data content server to self manage and distribute content based upon the visibility of content use and its ability to deliver the data content. The data content server becomes ‘self-aware’ for the purposes of application serving, typically based upon bandwidth usage, and can replicate data content to further servers in order to provide scaleable serving. The further server may be a server application that runs upon the data content server or it may be a further data content server. 
   According to another aspect of the present invention there is provided a data management system comprising a monitor unit and at least one data content server, the monitor unit including a processor and a storage device, the server including an input-output device, and the processor being arranged to run a monitor application that is stored upon the storage device, and in which the processor is further arranged to monitor the data content server&#39;s IO device when running the monitor application and to execute an action in response to a trigger condition associated with the IO device. 
   The monitor may itself he a resource server. 
   The data content server may have a processor arranged to monitor it&#39;s own IO device. 
   Typically the data stored on the servers will be file based data that is readily partitioned and for which access patterns are known or is predictable, for example video or audio data. Alternatively the data stored on the servers may be block based, for example a section of a database stored across several compute units can be copied when one of the compute units is heavily accessed and the network configuration may be altered appropriately. 
   The monitor unit may be arranged to monitor the server for faults. Alternatively, or additionally, the server may be arranged to self-monitor for faults. The monitor unit may be arranged to monitor the server ports and/or it may be arranged to monitor a client server network connection. The monitor unit may be arranged to spawn an appropriate server application either on a further port of the server or on a further server. The monitor unit may be arranged to facilitate the replication of the part of the data content of the server serviced by a failing port to a further server. This aims to ensure the continued and reliable supply of data to users. The monitor unit may update load balancing/routing tables which may be stored on the monitor unit. The monitor unit may also comprise a director server of other aspects of the invention, or indeed a resource server. 
   According to another aspect of the present invention there is provided a method of data management comprising the steps of:
     (i) monitoring traffic on at least one data content server on a network;   (ii) either or both of:
       (a) starting up or shutting down an appropriate data serving application automatically upon a further server on the network in response to network traffic;   (b) copying at least part of the data content of the data content server to the further server;   
       (iii) updating routing/load balancing tables associated with the network of resource servers; and   (iv) directing a portion of the network traffic to the further server.   

   The method may include providing the server as a server application upon the data content server or providing the server as a further data content server. 
   The method may include copying the at least part of the data content from either of the data content server or an original data source, for example a CD, DVD or tape media. This allows the data to be copied to the server even if the data content server has failed. The method may include executing steps (ii), (iii) and (iv) of the method in response to a change in network traffic due to any one of the following: application server failure, application server overload, insufficient nodes present upon a server based upon a statistical model. The method may include executing steps (ii), (iii) and (iv) of the method in response to a change in the number of active connections to a given port on the director unit. The method may include connecting or disconnecting a further server to/from a server farm in response to a variation in network traffic. The method may include configuring the further server within the network environment. 
   According to another aspect of the present invention there is provided a data structure for managing the automatic transfer of data between a server program and a further server program in response to a change in traffic on a network, the data structure being arranged to manage the distribution of the data over the server program and the further server program, the data structure having entries, each entry containing: 
   a locator associated with the server program; 
   an identifier associated with at least a portion of the data; and 
   statistics associated with network traffic between the server programs and the further server program. 
   The data structure may be arranged to distribute the data between the server program in response to the statistics, typically to improve the reliability of transfer of the data between the server program and the client program. The data structure may be arranged to facilitate the addition of further entries containing an additional locator, identifier and statistics thereto. The addition may occur in response to the statistical entries in the data structure. The statistics entries in the data structure may include entries relating to any one, or combination, of the following: usage of data, access patterns, access times, outgoing bit rates, accessed locations. The data structure may be arranged to facilitate to deletion of an existing entry therefrom. The deletion may occur in response to the statistical entries in the data structure. 
   The data structure may contain an entry containing a port identifier associated with each portion of the data, the port identifier may be a sub-set of the network address entry. The data structure may be arranged to copy the portion of the data associated with a port identifier from a first server program to a second program in response to a variation in the statistics relating to the network traffic. In the most preferred embodiments there is a port per video being served. 
   By “port” is meant a part of a logical network address (e.g. port 10020 from IP address 15.144.117.245). “Port” does not mean the network cabling connector of the NIC card. 
   The data structure may contain an entry relating to a threshold level of network traffic. The data structure may contain entries relating to upper and lower threshold levels of network traffic. Typically these threshold levels may be expressed as a ratio of the theoretical to actual deliverable capacity of an input-output (IO) device, typically a network interface card (NIC). 
   The server program and the further server program may be resident upon the same network element. There may be a plurality of server programs. 
   It will be appreciated that in many aspects of the present invention it is intended that the data is managed with minimal, preferably no, human intervention. 
   According to another aspect of the present invention there is provided a method of billing for access to data comprising the steps of:
     (i) logging a request for data;   (ii) logging the origin of the request;   (iii) generating a bill from data stored on a database;   (iv) issuing the bill.   

   The method may include marking data at a given price for use and/or type of use. The method may include logging a user&#39;s identifier. 
   According to another aspect of the present invention there is provided a method of data rental comprising the steps of:
         providing a server farm according to another aspect of the present invention either as a stand alone or as part of a library;   servicing a request for data from a user of the farm; and   charging the user for the supply of data.       

   According to an aspect of the present invention there is provided a method of maintaining availability of requested network resources comprises having a network of servers each having associated network-servable resources of a specific kind, and dynamically distributing servable resources between said resource servers dependent upon demand for said resources, thereby varying capability of said network as a whole to serve out a particular resource dependent upon the level of demand for said particular resource. 
   According to an aspect of the present invention there is provided a method of data management comprising the steps of:
     (i) monitoring traffic on at least one data content server on a network and/or software application response time for an application software running on at least one data content server on a network and   (ii) starting up or shutting down an appropriate data serving application automatically upon said server or upon a further server on the network in response to network traffic and/or application response time.   

   According to an aspect of the present invention there is provided a network of resource servers each having deliverable resource of a specific kind available for serving out, and a resource manager adapted to receive a demand indicator input indicative of demand for a particular one of said deliverable resources of said specific kind and to output a resource-varying output adapted to vary capability of said network as a whole to serve out said particular one resource. 
   According to an aspect of the present invention there is provided a network comprising a plurality of resource servers adapted to serve out servable resources of a specific kind;
         a usage monitor; and   a resource manager;
 
said usage monitor being adapted to monitor usage of said servable resources and to determine if a usage level of a particular said resource has changed significantly and to communicate such changes in usage level to said resource manager, said resource manager being adapted to introduce an additional server to said network and/or start up a resource serving application on a networked resource server if usage of said servable resources has increased significantly; and/or said resource manager being adapted to remove said specific resource from a networked resource server and/or shut down a resource-serving application on a networked resource server if said usage of said servable resources has decreased.
       

   According to an aspect of the present invention there is provided a resource management server adapted for use with a plurality of resource servers having resources of the same particular kind available for serving out, said resource management server being adapted to evaluate demand for a particular one of said resources of said specific kind, in use, in order to vary capacity of said network to serve out said particular one resource responsive to changes in demand for said particular one resource. 
   According to an aspect of the present invention there is provided a content management server adapted for use with a content server network, said content management server comprising a servable content monitor adapted to monitor levels of usage of servable content of a specific kind, and a content availability manager adapted to change the availability of specific servable content depending upon demand for said specific servable content; said content management server being adapted to introduce an additional resource server to a network and/or start up a content serving application on a content server if levels of usage of a particular content have increased significantly, and/or being adapted to remove content from a networked content server and/or shut down a content serving application on a content server if levels of usage of a particular content have decreased significantly. 
   According to an aspect of the present invention there is provided a resource management server adapted for use with a plurality of resource servers having resources of a common particular kind available for serving out, said resource management server having demand evaluation means adapted to evaluate demand for a particular one of said servable out resources of said specific kind, and capacity modifying means adapted to modify capacity of said network to serve out said particular one resource, said capacity modifying means being responsive to evaluated demand signals from said demand evaluation means. 
   According to an aspect of the present invention there is provided a network of video servers each having videos available for serving out, at least one of said video servers comprising a video migration manager adapted to receive video demand-indicative signals indicative of the level of demand on said network for said videos available for serving, and to cause either: (i) activation of video serving application software on a video server which has a copy of said particular video available, thereby making said particular video available for serving from said video server; or (ii) a particular video for which said demand is sufficiently high to be copied from a first video server where it is available for serving to a second, different, video server and to make said particular video available for serving from said second video server so as to increase the capacity of said network to serve out said particular video, or (iii) to cause a particular video for which said demand is sufficiently high to be servable out from an increased number of port addresses of a said video server where said particular video resides, thereby increasing capacity of said video server to serve out said particular video; or (iv) to be able to cause both any one of (i), (ii), or (iii) to occur, or any combination of (i), (ii) or (iii) to occur; and wherein said video migration manager is adapted to operate automatically without human intervention so as to dynamically distribute video serving capabilities over said video servers of said network, responsive to demand for said videos. 
   According to an aspect of the present invention there is provided a video server for use with a network of video servers each having videos available for serving out, said video server being capable of having videos available for serving out and further comprising a video migration manager adapted to receive video demand-indicative signals indicative of the level of demand on said network for said videos available for serving, and to cause either: (i) activation of video serving application software for a particular video, for which demand is sufficiently high, upon a video server that has said particular video in memory; or (ii) a particular video for which said demand is sufficiently high to be copied from a first video server where it is available for serving to a second, different, video server and to make available for serving from said second video server so as to increase the capacity of said network to serve out said particular video, or (iii) to cause a particular video for which said demand is sufficiently high to be servable out from an increased number of port addresses of a said video server where said particular video resides, thereby increasing capacity of said video server to serve out said particular video; or (iv) to be able to cause any one of, or any combination of, (i), (ii) or (iii) to occur; and wherein said video migration manager is adapted to operate automatically without human intervention so as to dynamically distribute video serving capabilities over said video servers of said network, responsive to demand for said videos. 
   According to an aspect of the present invention there is provided software for controlling the distribution of network resources over resource servers of a network, the software comprising a demand evaluation operative capable of establishing levels of demand for particular resources available on said network, and a resource allocation operative adapted to receive input from said demand evaluation operative and to cause: (i) resources to be copied from one resource server of said network to another resource server of said network thereby to increase capacity of said network to serve out said resource; or (ii) cause a specific resource to be started up and made servable out from at least one additional port address of a resource server that already has said specific resource in memory so as to increase capacity of said resource server to serve out said specific resource; or (iii) cause an additional server, not previously part of said network, to be co-opted into said network so as to increase capacity to serve out resources; or (iv) cause any one of, or combination of, (i), (ii) or (iii) to occur. 
   According to an aspect of the present invention there is provided a network of video servers each having videos available for serving out, at least one of said video servers comprising a video demand manager adapted to receive video demand-indicative signals indicative of the level of demand on said network for said videos available for serving, and to cause either: (i) deactivation of video serving application software on a video server which has a copy of said particular video available, thereby making said particular video unavailable for serving from said video server; or (ii) to cause a particular video for which said demand is sufficiently low to be servable out from a decreased number of port addresses of a said video server where said particular video resides, thereby decreasing capacity of said video server to serve out said particular video; or (iii) deleting from memory of a video server a video; or (iv) to be able to cause any one of (i), (ii), or (iii) to occur, or any combination of (i), (ii) or (iii) to occur; and wherein said video demand manager is adapted to operate automatically without human intervention so as to dynamically distribute video serving capabilities over said video servers of said network, responsive to demand for said videos. 
   According to an aspect of the present invention there is provided a video server for use with a network of video servers each having videos available for serving out, said video server being capable of having videos available for serving out and further comprising a video demand manager adapted to receive video demand-indicative signals indicative of the level of demand on said network for said videos available for serving, and to cause either: (i) deactivation of video serving application software for a particular video, for which demand is sufficiently low, upon a video server that has said particular video in memory; or (ii) deletion from a memory of a video server of a particular video for which said demand is sufficiently low so as to decrease the capacity of said network to serve out said particular video, or (iii) to cause a particular video for which said demand is sufficiently low to be servable out from a decreased number of port addresses of a said video server where said particular video resides, thereby decreasing capacity of said video server to serve out said particular video; or (iv) to be able to cause any one of, or any combination of, (i), (ii) or (iii) to occur; and wherein said video demand manager is adapted to operate automatically without human intervention so as to dynamically distribute video serving capabilities over said video servers of said network, responsive to demand for said videos. 
   According to an aspect of the present invention there is provided software for controlling the distribution of network resources over resource servers of a network, the software comprising a demand evaluation operative capable of establishing levels of demand for particular resources available on said network, and a resource allocation operative adapted to receive input from said demand evaluation operative and to cause modification of capacity of said network to serve out particular resources, said modification comprising an increase in capacity or a decrease in capacity to serve out a particular resource. 
   According to an aspect of the present invention there is provided a method of serving out video over a network of video servers comprising evaluating a capacity of said network as a whole to serve out specific video items by establishing for each video server in said network an established ability of each said server to serve out such said specific items that are potentially servable from said each video server; using said established abilities of each said video server to evaluate an overall capability of said network as whole to serve out each of said specific video items; and taking steps triggered by said overall capability of said network to vary said overall capability to serve out at least a selected one of said specific video items. 
   According to an aspect of the present invention there is provided a video server monitor for use with a network of video servers each of which having video items, said monitor comprising an input adapted to receive inputs, an output adapted to output outputs, and a processor adapted to process said inputs and generate said outputs, said inputs being representative of capabilities of each of said video servers to serve out video items potentially servable from respective said video servers; and said processor, in use, being capable of evaluating an overall capacity of said network from said inputs representative of each individual video server&#39;s capacity to serve out each said video item, and said processor being capable of using its evaluation of said overall capacity of said network to control output of said outputs, said outputs being adapted to vary said overall capacity of said network to serve out a selected one of said video items. 
   According to an aspect of the present invention there is provided a network of video servers having video items available for serving, and a video server monitor, said monitor comprising an input adapted to receive inputs, an output adapted to output outputs, and a processor adapted to process said inputs and generate said outputs, said inputs being representative of capabilities of each of said video servers to serve out video items potentially servable from respective said video servers; and said processor, in use, being capable of evaluating an overall capacity of said network from said inputs representative of each individual video server&#39;s capacity for each video item, and said processor being capable of using its evaluation of said overall capacity of said network to control said outputs, said outputs being adapted to vary said overall capacity of said network to serve out a selected one of said video items. 
   According to an aspect of the present invention there is provided a network of video servers wherein each video server is aware of its own capability to serve out videos that it has, and is aware of a capability of each other networked video server to serve out videos that they have, and wherein one of said video servers assumes a role of master video serving capacity controller and assesses a future capability of said network as a whole to serve out an additional copy of each video that is potentially servable in said network, and compares this assessed future capability for each video with threshold capabilities for each video and upon said assessed capability reaching said threshold capabilities said controller takes pre-programmed action automatically. 
   According to an aspect of the present invention there is provided a video server comprising processor means, memory means, and telecommunication means; said memory means having, or being adapted to have, video items for serving out of said video server; and said processor means being adapted to cause a said video item to be located in said memory means and served out of said telecommunication means to a network; and wherein said video server has input means for inputting to said processor inputs indicative of an ability of other video servers networked to said video server to serve out video items held on said other video servers, said processor monitoring an ability of said video server to serve out those of said video items held on said video server and being adapted to monitor, from said inputs, abilities of said other networked video servers to serve out video items held on said other video servers; said video server thereby being adapted to monitor an ability of said network to serve out particular said video items, and said processor having output means and being adapted to output outputs via said output means for causing said network to have an increased or reduced capacity to serve out at least a specific selected video item. 
   According to an aspect of the present invention there is provided software for running on a processor of a video server, said video server having a memory containing video items, an input port, a control output port, and a video streaming port, said software comprising a monitor routine adapted to process signals received by said input port from other video servers networked to said video server so as to establish a network-wide usage level of a plurality of videos items, or to establish a capacity of said network as a whole to serve out an additional copy of each of said video items potentially servable by said network; and said software having a video item availability-controlling routine which, pursuant to having established said usage level for each video item, causes actions to be taken to increase or decrease an ability of said network as a whole to serve out at least one specific video item. 
   According to an aspect of the present invention there is provided a method of modifying availability of video items on a network of video servers comprising providing a network of video servers wherein each video server is aware of its own capability to serve out videos that it has, and is aware of a capability of each other networked video server to serve out videos that they have, and wherein one of said video servers assumes a role of master video serving capacity controller and assesses a future capability of said network as a whole to serve out an additional copy of each video that is potentially servable in said network, and compares this assessed future capability for each video with threshold capabilities for each video, and upon said assessed capability reaching said threshold capabilities said controller takes pre-programmed action automatically. 
   According to an aspect of the present invention there is provided a video serving system comprising a monitor unit and at least one video content server, said monitor unit including a processor and a storage device having a monitor application stored upon it, said server including an input-output device, and said processor being arranged to run said monitor application, and in which said processor is further arranged to monitor said input/output device when running said monitor application and to execute an action in response to a trigger condition being met associated with said input/output device. 
   According to an aspect of the present invention there is provided a method of modifying availability of video items on a network of video servers comprising providing a network of video servers wherein each video server is aware of its own capability to serve out videos that it has, and an assessment of an aggregate capability of said network is made by aggregating individual video server capabilities, and modifying availabilities of videos on specific video servers so as to modify capability of said network as a whole to serve out specific particular video items. 
   According to an aspect of the present invention there is provided a method of maintaining availability of video farm or local area network resources comprises having a farm or local area of networked video servers each having associated network-servable videos and dynamically distributing videos between said video servers of said farm or local area network dependent upon demand for said videos, thereby varying capability of said farm or local area network as a whole to serve out a particular video dependent upon the level of demand for said particular video. 
   According to an aspect of the present invention there is provided a method of data storage management of data in a video farm or local area network comprising the steps of:
     (i) monitoring usage of video files;   (ii) determining if said usage of said video files has increased or decreased;   (iiia) introducing an additional video server to said farm or local area network and/or starting up a video-serving application on a video server if said usage has increased; and/or   (iiib) removing a said video file from a video server and/or shutting down a video-serving application on a video server if said usage has decreased.   

   According to an aspect of the present invention there is provided a method of rich media data management comprising the steps of:
     (i) monitoring traffic on at least one rich media data content server on a server farm or local area network and/or software application response time for an application software running on at least one rich media data content server on a server farm or local area network and   (ii) starting up or shutting down an appropriate rich media data serving application automatically upon said server or upon a further server on the farm or local area network in response to farm or network traffic and/or application response time.   

   According to an aspect of the present invention there is provided a video farm or local area network of video servers each having deliverable video resource of a specific kind available for serving out, and a resource manager adapted to receive a demand indicator input indicative of demand for a particular one of said deliverable video resources of said specific kind and to output a video resource-varying output adapted to vary capability of said video farm or local area network as a whole to serve out said particular one video resource. 
   According to an aspect of the present invention there is provided a video farm or local area network comprising a plurality of video servers adapted to serve out video resources of a specific kind;
         a usage monitor; and   a resource manager;
 
said usage monitor being adapted to monitor usage of said video resources and to determine if a usage level of a particular said resource has changed significantly and to communicate such changes in usage level to said resource manager, said resource manager being adapted to introduce an additional video server to said farm or local area network and/or start up a video resource serving application on a farm or networked video server if usage of said video resources has increased significantly; and/or said resource manager being adapted to remove said specific video resource from a farm server or local area networked video server and/or shut down a video resource-serving application on a farm server or local area networked video server if said usage of said video resource has decreased.
       

   According to an aspect of the present invention there is provided a rich media content management server adapted for use with a rich media content server farm or local area network, said rich media content management server comprising a servable rich media content monitor adapted to monitor levels of usage of servable rich media content of a specific kind, and a rich media content availability manager adapted to change the availability of specific servable rich media content depending upon demand for said specific servable rich media content; said rich media content management server being adapted to introduce an additional rich media resource server to a network and/or start up a rich media content serving application on a rich media content server if levels of usage of a particular rich media content have increased significantly, and/or being adapted to remove rich media content from a networked rich media content server and/or shut down a rich media content serving application on a rich media content server if levels of usage of a particular rich media content have decreased significantly. 
   According to an aspect of the present invention there is provided software for controlling the distribution of video serving applications over video servers of a video farm or network, the software comprising a demand evaluation operative capable of establishing levels of demand for particular video serving applications available on said farm or network, and a resource allocation operative adapted to receive input from said demand evaluation operative and to cause: (i) video serving applications to be copied from one video server of said farm or network to another video server of said farm or network thereby to increase capacity of said farm or network to serve out video files in a particular format; or (ii) cause a specific video serving application to be started up to enable a video file to be servable out from at least one additional port address of a video server that already has a video serving application so as to increase capacity of said video server to serve out a video file in a specific format; or (iii) cause an additional video server, not previously part of said farm or network, to be co-opted into said farm or network so as to increase capacity to serve out video serving applications; or (iv) cause any one of, or combination of, (i), (ii) or (iii) to occur. 
   According to an aspect of the present invention there is provided a method of maintaining availability of requested network resources comprises having a network of servers each having associated network-servable resources of a specific kind, and dynamically distributing servable resources between said resource servers dependent upon demand for said resources, thereby varying capability of said network as a whole to serve out a particular resource dependent upon the level of demand for said particular resource and wherein said resource servers have port addresses and a particular resource servable from a first port address is made available for serving from a second port address associated with the same server as said first port address. 
   According to an aspect of the present invention there is provided a method of maintaining availability of requested network resources comprises having a network of servers each having associated network-servable resources of a specific kind, and dynamically distributing servable resources between said resource servers dependent upon demand for said resources, thereby varying capability of said network as a whole to serve out a particular resource dependent upon the level of demand for said particular resource and wherein an additional resource server, not part of said network at a first time, joins said network in order to increase capacity of said network to serve out said particular resource, and wherein said additional resource server has said particular resource copied to it to enable said additional resource server to be capable of serving out said particular resource. 
   According to an aspect of the present invention there is provided a method of data storage management of data in a network comprising the steps of:
     (i) monitoring usage of a servable resource;   (ii) determining if said usage of said resource has increased or decreased;   (iiia) starting up a resource-serving application on a resource server if said usage has increased; and/or   (iiib) shutting down a resource-serving application on a resource server if said usage has decreased.   

   According to an aspect of the present invention there is provided a method of data management comprising the steps of:
     (i) monitoring traffic on at least one data content server on a network and/or software application response time for an application software running on at least one data content server on a network and   (ii) starting up or shutting down an appropriate data serving application automatically upon said server or upon a further server on the network in response to network traffic and/or application response time, wherein step (ii) is executed in response to a change in network traffic due to any of the following: data serving application failure, data serving application response time, data serving application overload of said server, insufficient servers having said data serving application present upon a server network based upon a statistical model.   

   According to an aspect of the present invention there is provided a network of resource servers each having deliverable resource of a specific kind available for serving out, and a resource manager adapted to receive a demand indicator input indicative of demand for a particular one of said deliverable resources of said specific kind and to output a resource-varying output adapted to vary capability of said network as a whole to serve out said particular one resource, and wherein said resource-varying output comprises a resource migration signal which causes said particular one resource to migrate from one resource server to another server. 
   According to an aspect of the present invention there is provided a network of resource servers each having deliverable resource of a specific kind available for serving out, and a resource manager adapted to receive a demand indicator input indicative of demand for a particular one of said deliverable resources of said specific kind and to output a resource-varying output adapted to vary capability of said network as a whole to serve out said particular one resource, and wherein said resource-varying output comprises a resource migration signal which causes said particular one resource to migrate from one resource server to another server, and wherein said resource servers have port addresses and wherein said particular one resource is available for serving from one port address of a said server and wherein said resource varying output causes either (i) a second port address of the same said server particular resource available for serving; or (ii) a reduction in serving capacity of said network as a whole to serve out said particular resource by reducing the port addresses of a said server operating to serve out said selected resource down from a plurality of port addresses to a smaller number of port addresses of that said server. 
   It will be understood that references to video both hereinbefore and hereinafter are taken to encompass video (visual), audio and any other streamed performances. 
   The invention will now be described, by way of example, with reference to the accompanying drawings, in which: 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram of a prior art data storage system; 
       FIG. 2  is a block diagram of a plurality of network telecommunications routes: 
       FIG. 3  is a schematic representation of a data storage system according to at least one aspect of the present invention; 
       FIG. 3   a  is a schematic representation of a modified version of the data storage system of  FIG. 3 ; 
       FIG. 4  is a schematic representation of a request data packet; 
       FIG. 5  is a schematic representation of a video data packet; 
       FIG. 6  is a schematic representation of a networked video library; 
       FIG. 7  is a flow chart detailing a method of data management according to an aspect of the present invention; 
       FIG. 8  is a flow chart detailing a method of data storage management according to an aspect of the present invention; 
       FIG. 9  is a flow chart detailing a method of credit management for data access according to an aspect of the present invention; 
       FIG. 10  schematically shows a web tier of Resource Servers in accordance with one aspect of the present invention; 
       FIG. 11  is a schematic representation of a prior art long haul video serving arrangement; 
       FIG. 12  is a schematic representation of a prior art Ethernet enabled video serving arrangement; 
       FIG. 13  is a schematic representation of an embodiment of a video serving arrangement according to an aspect of the present invention; 
       FIG. 14  is a representation of a routing/pricing table according to an aspect of the present invention; 
       FIG. 15  is a schematic representation of a long haul video serving arrangement incorporating an embodiment of the present invention; 
       FIG. 16  is a schematic representation of the video serving arrangement of  FIG. 13  showing the ‘master’/‘slave’ video server relationship; 
       FIG. 17  is a schematic representation of a master-slave video serving arrangement of  FIG. 16  with a redistribution of files between servers; 
       FIG. 18  is a schematic representation of the video serving arrangement of  FIG. 13  incorporating an additional data content server; 
       FIG. 19  is a flow chart of a method of data management according to an aspect of the present invention; 
       FIG. 20  is a flow chart of a functional step according to at least part of an aspect of the present invention; 
       FIG. 21  is a flowchart of a yet further functional step according to at least part of an aspect of the present invention; 
       FIG. 22  is a flowchart of a still further step functional step according to at least part of an aspect of the present invention; 
       FIG. 23  is a flowchart of a yet still further step functional step according to at least part of an aspect of the present invention; 
       FIG. 24  is a schematic representation of a prior art simple network management protocol (SNMP) network management system; 
       FIGS. 25   a  and  25   b  are prior art cluster arrangements for data management; 
       FIG. 26  is a schematic representation of a data management device according to an aspect of the present invention; 
       FIGS. 27   a  and  27   b  are schematic representations of other examples similar to that of  FIG. 26 ; 
       FIG. 28  is a schematic representation of a data management system according to an aspect of the present invention; and 
       FIG. 28   a  is a flow chart detailing a method of data management according to the present invention. 
       FIG. 29  shows a LAN of video servers, comprising a video farm; 
       FIG. 30  shows a video server of  FIG. 29 ; 
       FIG. 31  shows a monitoring routine of the video farm of  FIG. 29 ; 
       FIG. 32  shows another monitoring routine of the video farm of  FIG. 29 ; 
       FIG. 33  shows schematically checking movie usage; and 
       FIG. 34  shows schematically checking bandwidth usage. 
   

   DETAILED DESCRIPTION OF THE DRAWINGS 
     FIG. 1  shows a typical prior art arrangement for infrastructure for an internet service provider, for example an on-line retailer. The infrastructure typically comprises three layers, a web-tier  11 , an application tier  12 , and a database tier  13  connected by switches  14 . The web-tier has a large number typically, 100 or 200 of highly distributed servers  15  each with a small amount of attached storage (e.g. 100 GB) each having the same data content replicated thereupon to ensure that a large number of external users can access the data (i.e. the same data can be accessed on a large number of servers  15 , using an even larger number of telecoms routes). The data upon the web-tier  11  is usually is the form of static hypertext mark up language (HTML) pages. The HTML pages do not require a great deal of memory. The application tier  12  has fewer servers  16  than the web-tier  11  and runs the applications. A network switch, or router,  14  that sits above the web-tier  15  directs external users to the web-tier server  15  that is next in line for a request, load balancing the user request for data over the servers  15  in a crude way. The database tier  13  has a very small number, typically only 1 or 2, large capacity servers  16  connected to, high end large capacity e.g. hundreds of GB to tens of TB, consolidated storage elements  17  that are typically very expensive, e.g. $100 k high end disc arrays. The storage elements  17  contain data relating to, for example user details, user profiles, stock and auction details for the retailer. A user, referenced  5 , accesses the data on the web-tier  11  via the web-tier  11 , the application tier  12 , and particularly via the switches or routers  14 . The switches or routers are typically level 2, level 3, or perhaps level 4, switches. 
   Each tier of the infrastructure processes the data as best it can and the passes the data down to the tier below it. One problem with this approach is the increasing cost of the lower tier devices coupled with the need to replicate the devices at least once in order to build fault tolerance into the system. 
   Systems in which placement of network attached storage (NAS) at the web-tier are used are not particularly efficient as the web-tier servers do not have sufficient network connections to satisfy the information demands placed upon them by users in such architectures (see for example  FIG. 2 ) and, NAS boxes have relatively few network connections. The cost of placing high end disc arrays, fibre channel and switches in the web-tier is prohibitive due to the large number of servers and the cost of Fibre channel adapter cards and disc arrays for the web tier is simply uneconomic. 
   Each content, or resource,  15  server has identical content capable of being served out to the user  5 . This reduces the data management burden on the router/switches  14 , allowing “dumber” switches to be used. 
   In at least one embodiment of at least an aspect of the present invention the following definitions can be applied: 
   Server farm: a collection of servers acting together to provide a given application type (for example video streaming). In many embodiments of the invention a server farm will provide a load balanced delivery of content to users requesting use of that content from the farm. The user will, potentially, be able to access content on all servers of the farm using a single web address, so far as the user is concerned. 
   Demand Director: a server acting as a management and co-ordinating station within a server farm for determining the location of content across the servers of the farm, and capable of directing a request for a specific resource to an appropriate resource server that contains that resource. 
   Resource Server: a server device capable of serving out a resource which can be requested by a user. Typically a general purpose PC type hardware with some storage associated, e.g. internal disc, external disc array, in order to house the content, or resource, to be delivered. 
     FIG. 2  illustrates a server  20  connected to a router  14  which is in turn connected to the internet by a plurality of different telecommunications links  22   a ,  22   b ,  22   c ,  22   d ,  22   e.    
     FIG. 3  shows a networked video server farm  302 , in accordance with at least part of an aspect of the present invention, comprising a director unit  304  and a plurality of resource servers  306   a - n . Instead of “farm”, the reader could read “network”. A farm is a sub-class of a network, characterised by the servers all being “local” in the sense of local in telecommunications terms: i.e. they can communicate easily with the requesting demand director. Often this is because they are truly geographically local—e.g. in the same room or building, but “local” can mean “bandwidth/telecoms” local—i.e. good telecoms links between the server and the demand director. The farm  302  is connected to an external network  308 , typically the Internet or a MAN (Metropolitan Area Network). 
   A typical server farm, say for serving out video movies, may comprise around forty content, or resource, servers and a demand director in a nineteen-inch wide rack. The typical farm will be able to store up to seven thousand feature length videos, each video being about 2 GigaBytes (GB) in size. 
   The director unit  304  has an interface  309  thereupon which specifies upon which ports  310   a - c  a resource-serving application is listening and which of the resource servers  306   a - n  are able to participate in serving out that application resource. For example two resource servers  306   b ,  306   a  are able to serve port 10045 requests for hypertext transfer protocol (HTTP) type application data (a resource capable of being served out), and all of the resource servers  306   a - n  are able to serve requests for real time streaming protocol (RTSP) application data. Other ports may be able to serve file transfer protocol (FTP) requests. Thus there may be different categories of servable resources, and each resource server may not be able to serve out all categories (or perhaps they can). 
   The video data can be partitioned into groups that are located on a per resource server basis. Serving the videos on a per resource server  306   a - n  basis allows a video to be tracked and a determination made as to how busy/popular any given video is. 
   The director unit  304  contains a database  311  which, in the current embodiment, contains details of real time videos  312   a - h  and upon which of the compute units  306 - n  the videos  312   a - h  are stored. The database  311  can determine which resource server  306   a - n  has a port suitable for serving new content as it is introduced onto the farm  302 . Typically, a video will stick to a specified port. Video operates in a predictable manner and is deterministic in nature, i.e. the input/output ( 10 ) requirements are well understood. For example, —if a video is read back from a disc subsystem it is highly likely that the video will be read sequentially from the disc during playback. Thus, the capacity per resource server can be readily estimated. It will be appreciated that the data stored on the resource servers need not be video data: it may be audio data or any other data set where data access patterns are predictable and the data is readily partitioned, as the data is already divided into objects—the files e.g. NAS devices that serve files can also be implemented using this scheme in order to provide greater scalability than is currently available. 
   Each resource server  306   a - n  has two network interface cards (NIC)  313   a - b , one for communication with the demand director unit  304  and one for outputting data to the network  308 . 
   A user  314  connected to the network  308  requests a video  312   a  that is stored on the farm  302 . The request is passed from a user&#39;s terminal  316  via the network  308  to the demand director unit  304 . The director unit  304  compares the request to the contents of the database  311  to ascertain if the requested video (requested resource) is present on the farm  302 . If the requested video is not present on the farm the demand director unit  304  returns an error message to the user  314 . 
   Should the requested video be present on the farm  302  the demand director unit  304  accesses the database  311  in order to find a resource server  306   d  that has the video stored upon it. If more than resource server  306   d ,  306   j  has the requested video upon it the demand director unit  304  checks to see which of the resource servers  306   d ,  306   j  is best placed to serve out the requested video. This load balancing is typically achieved by monitoring one or more of the bandwidth available to a resource server, whether the resource server is currently being accessed either for the request severing out the same resource or for serving out another video, or possibly even projected access requirements based upon previous access demands placed upon a resource server. This load balancing is more sophisticated than the prior art “Round-Robin” or “response time” based approaches. 
   For example, resource server  306   f  may have the most popular video  312   b  stored upon it along with all of the other resource servers  306   a - e ,  306   g - n  in the farm  302 . The server  306   f  may also have a previously unpopular video  312   c  stored upon it. The previously unpopular video  312   c  may increase in popularity, with the increase in access being recorded at the director unit  304 . Thus, when the next request for the most popular video  312   b  is received by the demand director unit  304  it knows that the computer unit  306   f  is likely to be accessed for the video that is increasing in popularity  312   c , and will therefore use one of the other compute units  306   a - e,g - n  to service this request for the most popular video  312   b  (assuming that they have available unused serving-out capacity). 
   Once the demand director unit  304  has established which of the resource servers  306   a - n  for example  306   d , it intends to service the request for the video  312   a  it strips TCP/IP address information  402  from a data packet  404  containing the request, as shown in  FIG. 4 , and splices a replacement TCP/IP header  402   a  containing the network address of the resource server  306   d  to the payload of the data packet  404 , as is known from standard routing techniques. The request data packet  404  is forwarded to the compute unit  304 , typically via an Ethernet link. 
   The resource server  306   d  will have the desired video file available for serving out to the user. As shown in  FIG. 5 , prior to streaming the requested video directly to the user  316  the resource server  306   d  rewrites a TCP/IP header  502  corresponding to the network address of the demand director unit  304  to the payload  504  of each outgoing data packet  506  containing the streamed video data. The video data will typically be in real time format, although it may be MPEG, Real Networks format or Windows Media format. The direct nature of the streaming bypasses the demand director unit  304  resulting in the removal of a potential bottleneck in the data transfer. The data is usually streamed via a telecommunication network. 
   The effect of placing the network address of the demand director unit  304  in the header  502  is to create a one time virtual connection  318  between the user terminal  316  and the demand director unit  304 . This hides the network address of the resource server  306   d  whilst allowing the user  314  to play the video multiple times whilst the virtual connection  318  is maintained, in a manner similar to the rental of video cassettes. However, once the ephemeral virtual connection  318  is broken the user  314  has no means of re-accessing the video without accessing the demand director unit  304 , as they do not know the network address of the resource server  306   d  that served the data to them. This arrangement limits the opportunities for a user to copy the data, or view it again at a later time, as the serving protocols are not the same as those used by a NAS that serves out data as raw files. 
   One of the resource servers  306   a - n , or the demand director  304 , can act as a billing unit  306   c . The user may be required to provide details such as their e-mail address, address, telephone number and bank details before they are allowed full access to the farm  302 . The billing unit  306   c  receives information from the director unit relating to the users details, the video that the user has requested and the cost of viewing the video. Thus, the billing unit  306   c  can automatically produce and issue bills to users of the farm  302  based upon their viewing habits. Where the users bank account details are retained by the billing unit  306   c  payment for viewed videos can be taken from a users bank account. Typically billing occurs three days or so after viewing the video or on a regular basis, for example monthly, and any subscription fee for the use of the service can be billed at the same time. 
   It will be appreciated that video clips can be provided as a ‘free trial’ service for potential users of the video farm. 
   As the demand for a particular video increases the demand director  304  writes the popular video data to additional resource servers  306   d - n  that are within the server farm  302 . Should the demand for a video increase so much that there are not sufficient resource servers  306  within the farm  302  the demand director  304  co-opts additional resource servers  306   o - s  to the server farm  302 . These additional compute units may be on other server farms connected to a MAN, as detailed hereinafter. Alternatively, they may be additional, non-utilised, resource servers associated with the farm  302 . 
   The non-utilised compute resources are typically added to the server farm  302  as demand begins to increase. The horizontal scalability of compute resources allows an xSP (e.g. SSP, ASP, ISP, or FSP) to start with a small amount of relatively cheap infrastructure and increase their access provision in line with demand. 
   As will be appreciated, because there is asymmetric, different, data on the web tier resource servers  306 , it is easy to add extra new, different resources, (e.g. videos). A new video, or other resource is provided on a networked resource server  306  and the demand director  304  is updated to be aware of the existence of the new resource capable of being served out, and of its location on the network (so that it can accept a request for the newly available resource and direct requests to the correct resource server). 
   Similarly, it is straightforward to add additional serving capacity. A new resource server is simply connected to the network and the demand director informed of its existence/presence on the network and what resources it has for serving out. 
   By way of example, new releases of video movies could simply be loaded into a new video server and the new server connected to the network. Alternatively or additionally, old, unused, videos could be overwritten with more popular videos, or newer videos. So long as the demand director knows what is on the network capable of being served out, and where it is, the demand director can communicate a user with requested resource. 
   Altering the content servable out from a resource server may be done with human intervention/manually, or a computer such as the demand director, may automatically re-distribute resources over the network in order to be able better to serve out often-requested resources. This may involve automatically copying resources either to provide multiple copies of the resource with a resource server, or copies on an additional, or different, server. 
   Once one is freed from the conventional straightjacket of having all web tier servers have the same serverable content, things become much easier to change. There is, of course, an increase in the overhead in managing the knowledge of what resource is where, and this requires a smarter demand director than the prior art. The decision to go against the conventional mantra that all resource servers capable of serving a particular kind of resource (e.g. videos) have the same variety of and number of available resources of that specific kind of resource, has very significant advantages. 
   Returning to  FIG. 3 , as demand for a particular video decreases the demand director unit  304  removes this video data from some of the resource servers  306   k - n  within the farm  302 . Alternatively, the demand director  304  stops the unpopular application serving on the resource servers  306   k - n  and leaves the content in situ. Should the overall demand for videos drop to a low enough level the director unit  304  retires resource servers from the server farm  302 . Those resource servers that are retired can be recalled to the server farm  302  should the demand increase again, or co-opted to other farms on a MAN, see hereinafter. Alternatively, or additionally, typically in the case of a chronic shortage of disc space, the demand director unit  304  may overwrite unpopular video files, as determined by a statistical analysis that it may perform on the existing resource servers  306   a - n  with more popular video files. Thus is it possible that any one of the resource servers  306   a - n  may have more than one copy of a video on it at any given time. More likely, however, is to have one copy of a specific video file on a video server and run more serving processes on the video server to serve out to different users, using the same video file. An advantage of having more than copy of a video file on the same server is so as not to overly tax the disc on which that video file is housed. 
   Thus, the server farm  302  is horizontally scaleable and dynamically expandable. This enables the provision of content level granularity. The amount of resource-serving capacity dedicated to a particular resource (e.g. video) can be dynamically changed depending upon demand. 
     FIG. 3   a  shows a modified version of a server farm  302 ′ similar to the server farm  302  of  FIG. 3  in which three demand director  304 ′  a - c  are provided in order to build fault tolerance into the system  302 ′. Additionally, some of the resource servers  306 ′ d - f  have additional storage associated with them either in the form of DAS  320 ′ or NAS  322 ′. The DAS is typically connected to the units  306 ′ d - f  by a SCSI or Ethernet link. Thus, the horizontal scalability of this arrangement is evident. 
   The demand director  304 ′ a  is shown servicing two requests for data to two users  314 ′ a,b  via respective resource servers  306 ′ b,d . The data is transferred to the users  314 ′ a,b  via respective networks  308 ′ a,b  in the manner described hereinbefore. The users  314 ′ a,b  start their session by connecting to the resource servers  306 ′ b,d  via the demand director unit  304 ′ a . Thereafter the users  314 ′ a,b  are connected directly to the resource servers  306 ′ b,d.    
     FIG. 6 , shows a MAN  602  having several server farms  604   a - d  connected thereto. Each of the farms  604   a - d  has its own demand director  606   a - d  and resource servers  608   a - d ,  608 ′ a - d  thereupon. Each of the demand directors  606   a - d  has a database  610   a - d  that contains details of the video content of each of resource servers  608   a - d ,  608 ′ a - d . The farms  604   a - d  are typically situated in multiple occupancy dwellings  611   a - d  such as condominiums or apartment blocks, usually in the basement or service area. When one of the demand directors  606   a  receives a request for a particular video it accesses database  610   a  which is stored thereupon to see which, if any, of the resource servers  608   a - d ,  608 ′ a - d  has the required video data stored upon it. 
   If none of the resource servers  608   a - d ,  608 ′ a - d  has the video data the demand director  604   a  issues a notification of that fact to the user who requested the video. There may be multiple databases, for example, each dwelling  611   a - d  may have a self-contained farm and does not need to go outside its own farm to find content (videos). However, a dwelling&#39;s farm may extract content from other dwellings&#39; farms, as necessary. 
   If at least one of the resource servers  608   a - d ,  608 ′ a - d  has the required video data upon it the demand director unit  604   a  uses the database  610   a  to decide which of the resource servers  608   c ,  608   b  is best placed to serve out the data, i.e. which resource server  608   c ,  608 ′ b  has the most available output bandwidth, which has its CPU not currently being over-used etc. 
   Once the decisions as to which resource server  608   c  is accessed in order to fulfil the request for the data the databases  610   a - d  are updated to show the resource server  608   c  as being utilised. 
   The packet headers sent between the demand director  606   a  and the resource server  608   c , and between the compute unit resource server  608   c  and a requester  612  are re-written such that a virtual connection  614  between the demand director unit  606   a  and the user, and between the resource server and the user, is established as described hereinbefore. The packets appear to the recipient user to have come from the demand director, which is where the user was expecting them to come from. 
   The arrangement allows data content to be further distributed over the server farms  604   a - d  forming a library without each farm having to maintain the full data content of the library. For example a first set of  100  different videos could be stored in one server and a second different, set of  100  videos (different from each other and from that of the first set) could be stored on a second server. 
   Data can be added to, or removed from each farm and additional resource servers added or removed from the farms as described hereinbefore. 
   Additionally, one of the demand director units  606   c  can operate as a central billing facility where all requests for video, wherever that request originates e.g. apartment building  611   a  and whichever farm  604   a - d  services the request, are logged and billed. This central billing facility bills users of the system in the same manner as the billing unit  306   c  for the single server  302 . 
   In both the individual farm, or the MAN connected library of farms, the content is loaded-onto the resource servers from a variety of sources. For example the content can be loaded directly from a video cassette or DVD. Alternatively, the content may be downloaded onto the resource servers over a network, typically the internet from other resource servers, or via a network (typically the Internet), from a film studio or film archive, or from a tape library connected to the server farm  302 , or via a satellite download. 
     FIG. 7  is a flowchart detailing the methodology used in a server farm. The director unit  304  receives a request for a file (e.g. video or audio) from a user (step  700 ), typically the user will be presented with a selection of videos from which to choose. The demand director  304  accesses the database  311  in order to ascertain if the file is stored on the farm (step  702 ). If the file is not stored on the farm the demand director  304  sends a notice to that effect to the user  314  (step  704 ). 
   If the file is stored on the farm the demand director  304  accesses the database to check how many of the resource servers  306   a - n  are available to service the request for the file (step  705 ) and logs the request in a statistical model (step  706 . Resource server  306   f  has the requested file stored upon it. There are a number of options available to the demand director unit  304 . 
   If the statistical model has calculated an increase in the number of requests for the file and there is a possibility that the resource server  306   f  may not be able to serve all of the requests for the file. The demand director  304  can copy the file to an additional resource server(s)  306   g - n  the (step  708 ) and update its database  311  (step  709 ). Also, if the other resource servers  306   a - e ,  306   g - n  within the farm are near their capacity the demand director unit  304  can connect to additional resource servers, possibly having been previously retired from the farm, in order to use their storage and connection capacity (step  710 ), and can copy the requested file to one of them (step  712 ) and update its database  311  (step  713 ). Alternatively the director unit  304  can start up additional service providing applications on the resource servers  306   f.    
   Should the demand director unit  304  establish that there is more than one resource server  306   f ,  306   i  capable of serving a request for a file the demand director unit  304  executes a load balancing routine (step  714 ) to ascertain which of the resource servers  306   f ,  306   i  is best placed to serve out the requested resource, for example by looking at the database in order to determine the current server activity, or by using the statistical model, or it may use a simple round-robin scheme. 
   If there is no reason why the resource server  306   f  is incapable of dealing with the request the demand director unit forwards a TCP/IP packet of the request for the file (step  715 ) to a first, inward, NIC  313   a  of the resource server  306   f  (step  716 ). Prior to outputting the file the resource unit  306   f  writes the TCP/IP header of the output data packets such that it appears to the user&#39;s machine that they issue from the demand director unit  304  (step  718 ) thus establishing the one time virtual connection  318  between the demand director unit and the user&#39;s machine  316 . The symbolic link creation is referenced as  720 . Step  722  outputs the file from the resource server  306  to the user via a suitable port of the second, outward, NIC  313   b , over the network  308 . The resource server  306  checks periodically, referenced  724 , to see if some of the requested content is still to be served out. If there is still remaining content the server  306  continues to re-write packet headers ( 718 ). If there is more content to serve out the network connection of the server  306  is closed down (referenced  726 ). 
   Once a resource server  306   f  is found that can service the request the file is sent via the network  308  to the user  314  as described previously (steps  714720 ). The user is free to view the file for as long as the symbolic link is maintained on the file system and as long as the resource application being run on the resource server has a free resource to service the client&#39;s request. The symbolic link may have a time limit. The demand director unit  304  may include a trusted clock which is checked periodically to see if the symbolic link has expired (step  728 ). If the time limit for the link has expired the demand director unit  304  issues an instruction to the resource server  306   f  to sever the link (step  730 ), i.e. remove the file system&#39;s symbolic link to the content or drop support for the resource application being run on the resource server, typically by disabling the resource server&#39;s packet rewriting ability. Alternatively or additionally, the resource server may by default remove the link after a predetermined time. 
   As a particular file becomes less popular the database will record less requests for it until at a threshold value, for example no requests within a week, two weeks or a month, the demand director  304  will issue an instruction to a resource server  306   d  which contains the file to delete all but a single copy of the file (step  732 ) and which leaves the content of the last copy of the video file of a server in situ on the server and shut down (step  734 ) the resource application running on the resource server  306   f . This process will continue repeatedly over a period of time until all of the copies of the file have been disabled from all of the resource servers  306   d ,  306   k ,  306   j  that had the file stored upon them (if demand falls off to the extent to justify that). Alternatively, the threshold can be set such that all of the copies of the file are disabled from any resource server once the threshold is passed. It is possible to delete a file from a resource server if it is unpopular, and this may be a preferred option sometimes, but since it is expensive in I/O telecoms to re-load a file to a server, it is usually preferred to de-select the file by closing the serving out application for that file running on the server. 
   Referring now to  FIG. 8 , the demand director  304  also monitors the total usage of the farm as the usage varies (step  802 ). As the total number of requests for files decreases the director unit  304  moves files between resource servers  306  to minimise the number of resource servers  306  required to service the estimated number of requests for the files (step  804 ). This enables redundant resource servers  306  to be retired from the farm  302  (step  806 ). The demand director unit  304  updates the database to reflect the redistribution of files and the retired resource servers (step  808 ). 
   As usage of the farm increases toward the capacity of the existing resource servers  306   a - n  the director unit  304  introduces additional resource servers  306   o - s  into the farm  302  (step  810 ) and copies some of the files to these additional resource servers  306   o - s  (step  812 ). The files copied to these additional resource servers  306   o - s  will typically be the most popular files. The demand director also starts up appropriate resource application serving programs on the resource servers  306   o - s  upon their addition to the farm. However, this may not be the case. If, for example, the additional resource servers  306   o - s  have a lower specification that those already in the farm  306   a - n  the demand director may copy less frequently requested files to the additional resource servers  306   o - s  to enable it to cause more copies of the most popular files to be created on the high specification resource servers  306   o - s , in order to guarantee high quality access to the more popular files. Once the additional resource servers  306   o - s  have been introduced into the farm  302 , their content and application serving capabilities are uploaded into the demand director&#39;s database  311  (step  814 ). 
   Referring now to  FIG. 9 , one of the resource servers  306   c , or the demand director  304 , can act as a billing unit. The billing unit logs an incoming request for a file (step  902 ) including the network address of the requesters computer and the requesters identification. The billing unit then causes bills to be issued to the user (step  904 ). The bill can be for access to individual file (step  906 ) typically billed by direct debit in three working days from a users bank account, the bank account details being held on a database. Alternatively, the billing unit can produce a bill for the billing period (step  907 ) typically a day, or a week, or a month, and the bill can include a subscription charge, if one is levied. This ‘period’ bill can be automatically deducted from a bank account (step  908 ) or sent to the user for manual payment (step  910 ). 
     FIG. 10  shows a new web tier, referenced  1000 , with resource servers  15 ′ and a demand director  14 ′, as discussed, with different resources of the same kind on the web tier servers  15 ′, and the demand director having a “map” of where to find requested resources. 
   It will be appreciated that it is new in a web tier of an Application Service Provider to have a demand director know where different resources are non-homogeneously distributed over a plurality of web tier servers, each of which has the same type of resource available for serving (e.g. videos, audio, data records, streamed media products), but which have different resource content, all accessible to a user by inputting the same www address. This model is more flexible than the previously sacrosanct “all content-servers have the same content” model when it comes to expanding the available resources/content (e.g. increasing the number of videos). It is not necessary to modify existing web tier servers in order to add another with different content. However, it may be desirable to do so to remove unwanted content from either being available for serving out—e.g. by stopping running the software necessary to serve out that unwanted resource, or removing it from the available resource database in the demand director, or by deleting or overwriting the resource/content with more desirable content. This avoids an increasing amount of infrequently accessed content/resource—which is wasteful in memory and/or processing capacity of the web tier servers. 
   It is known to have different web tier servers (accessible by the same address as seen by the user) have different content/resources in the sense of a first web tier server may have one category of resource available for serving (e.g. music) and another may have a different category of resource (e.g. car prices) but there has previously been a prejudice against having dissimilar source-category content/resource on different web tier servers of the same ASP. 
   There may be a plurality of farms connected to a MAN. Each farm may have a portion of data stored thereupon; the sum of the data stored on the farms may be a library. 
     FIG. 10  also illustrates, in principle, and in comparison with  FIG. 3 , using similar reference numerals, how simple the new arrangement is in comparison with the prior art of  FIG. 3 . The web tier  11 , application tier  12 , and database tier  13 , and their associated switches, have been replaced by the single tier, web tier  1000 , and the relatively dumb level 2, 3, 4 switches  14  have been replaced by a demand director, effectively level 7 switch  14 ′. 
   This makes it much easier for new companies to set up a web tier. They need to buy some resource servers (which could be practically PC&#39;s or PC-like), and buy a demand director (which could also be a PC), install the appropriate control software, and install appropriate resources (e.g. videos). This is much easier, and cheaper, than establishing the complex and expensive infrastructure of  FIG. 3 . An ASP could now be set up in a garage provided appropriate telecoms to the www were available. 
   It will be appreciated that in practice it may be desirable to build in some redundancy to the demand director: perhaps have more than one demand director, with one acting as a slave to the other until the master develops a fault, at which point the slave, with mirror records and functionality, takes over. It may be desirable to have a copy of each resource on at least two resource servers (Raid 1 files in case a resource server develops a fault). 
   Partitioning the available resources onto different resource servers works well with partitionable content/resources. Each resource/content has an identify distinct from others in its class, and this facilitates partitioning. A large integrated database may be difficult to partition between different resource servers—but perhaps it could be done. Files are readily partitionable. The fact that in video serving the resource is a datastream of content also makes it worthwhile to increase the complexity and overhead of finding the video on the web-tier, because once a user is connected to the video resource they will stay connected for a significant time whilst the video content is streamed to them. If the content were of small size, and the user—web tier server connection time were small, the increase in data content management may not be worthwhile. In a typical example a user may stay connected to a web-tier video steaming server for of the order of 10 minutes, 20 minutes, 30 minutes, 60 minutes, 90 minutes, depending upon the bandwidth of the telecoms and the size of buffer/memory available at the user&#39;s end into which the video can be stored. As technology improves this time may be shorter. 
   The invention works well for read-only access to the resource servers. 
   Whilst serving of video moves has been the main example it is also envisaged that the invention can have significant uses in other areas. As an example there is e-learning. Streaming a rich media product (e.g. video, audio, multi-media performance, etc.) using the invention can be used for teaching or training. Schools could use the invention, as could companies for corporate training/education. Tailored training packages can be easily added to a website using the present invention—it is easier to change resource content with the present invention. A user could receive an educational video; or an interactive session with streamed rich media coming to him (e.g. video clips, pictures, questions, forms, music, games, etc.); or a non-interactive, read-only, session with the above. In a structured learning programme the ASP could make different modules available at different times (e.g. add more complex/higher level training after more basic training). The speed and ease at which served out data content can be changed could be very useful. 
   There now follows a consideration in more detail of how the serving out of videos may be implemented in a Metropolitan Area Network (MAN). 
   Referring now to  FIG. 11  which shows a prior art arrangement, a long haul video serving arrangement comprises a video farm 1110, a server local area network (LAN)  1112 , typically an Ethernet, long haul infrastructure  1114  typically a switched frame relay system, e.g. using ATM, such as SONET, a client LAN  1116  and a client machine  1118 , or user  1118 . 
   The client machine  1118  issues a request for a video stored on the video farm  1110 . This request is passed over the client LAN  1116 , the long haul infrastructure  1116 , the server LAN  1112  to the video farm  1110  where the request is serviced, i.e. the requested video file is accessed. The file is transmitted from the video farm  1110  via the server LAN  1112  to the long haul infrastructure  1114  where it is placed into cells for transmission via the fast frame switched network to the client LAN  1116 . The transmitted data is reassembled at the interface between the infrastructure  1114  and the LAN  1116 . The client views the video on the client machine  1118 . 
   This arrangement has the problem that the long haul infrastructure  1114  is costly to install and maintain. Also the cellularisation of the data introduces a point at which transcription errors can occur or data be lost. 
   Typically, long haul networks typically consist of networks that are owned by telecommunication carriers. Data passes between these carriers&#39; networks through peering relationships that are not actively managed and hence can cause quality issues such as packet loss. 
   Referring now to  FIG. 12 , another prior art arrangement, a number of video servers  1120   a - d  (resource servers) are connected to a LAN  1122 , typically an Ethernet. All of the servers  1120   a - d  have the same video content  1124   a - e  thereupon (in the prior art) and there is no awareness of load being placed upon any single server or file. This is the current nature of video serving on LAN&#39;s, metropolitan area networks (MAN) and the Internet; massive over-provision of capacity in order to ensure the availability of data to a client. 
   Referring now to  FIG. 13 , an embodiment of the present invention, a federated video serving arrangement  1300  comprises a plurality of distributed video servers,  1302   a - c , connected to a MAN  1304 , a gateway  1306  to the MAN  304  which is connected to a LAN  1308  having client workstations (users)  1310   a - c  attached thereto. 
   A user on one of the workstations  1310   b  requests a video. The request is transmitted over the LAN  1308 , typically an Ethernet, to the MAN  1304  via the gateway  1306 . The MAN  1304 , which is also typically an Ethernet, has the distributed video servers  1302   a - c  connected thereto. One of the servers  1302   b  acts as a master server, or demand director server, and the request for the video is forwarded by the gateway to this master demand director server  1302   b.    
   The demand director master server  1302   b  stores a table  1400 , as shown in  FIG. 14 , having entries relating to a resource server identifier  1401  a network address  1402  associated with each resource server, typically an internet protocol (IP) address, each resource server&#39;s data content  1404 , pricing information for each data file  1406 , and the current bandwidth usage  1408  associated with each resource server. The demand director master server  1302   b  interrogates the table  1400  in order to ascertain which resource server  1302   a - c  is best placed to service a request for data. 
   The resource servers  1302   a - c  do not necessarily have the same data content upon each of them. Indeed, it is usual that each server  1302   a - c  will have at least partially dissimilar content to any other of the servers in order to maximise the data content available over the MAN. In many instances different servers will have wholly dissimilar content thereupon, or at least substantially so. The MAN will typically cover a conurbation and each of the resource servers will usually be situated in a separate building. The building is typically a multiple occupancy dwelling, such as a condominium or an apartment building. Alternatively, the building may be a service provider&#39;s office or a designated server building. 
   The demand director master server  1302   b  and the ‘slave’ servers  1302   a - c  (resource servers) use an internet video streaming protocol (IVSP), that will be detailed hereinafter, in order to monitor the usage and manage the data content distributed over the servers  1302   a - c.    
   The master server  1302   b  ascertains which of the servers  1302   a - c  is best placed to service the demand and the video data is transmitted via the MAN and Ethernet to the client machine  1118  using a packet based transmission protocol such as, for example, carrier sense multiple access with collision detection (CSMA/CD) or user datagram protocol (UDP). 
   The master server  1304   b  updates the table  1400  in order to account for the request being serviced should a new request for data be made. The table  1400  is updated using the protocol that is described hereinafter. 
   Should the master server  1302   b  fail or become disconnected from the MAN  1304  the slave servers  1302   a,c  will detect this, as they will not receive a reply to a request or response (that they periodically send out), and the first of the slave servers  1302   a  to detect the failure of the master server  1302   b  will assume the role of master, demand director, server. The new master, demand director, server  1302   a  builds a table that is analogous to that held by the failed master server  1302   b  by interrogating the remaining servers, in this example there is only the one remaining server  1302   c  although there may be a plurality of other slave, resource-providing, servers. 
   The master server  1306   b  can act as a centralised billing unit that correlates a clients access to data with the cost of the data and generates a bill. The bill can be either sent to the client via E-mail or conventional mail, deducted directly from a client&#39;s bank account, or added to the user&#39;s service provider&#39;s, or cable operator&#39;s, bill. 
   For example, a client&#39;s bill may be made up of 20% access to server A, 5% to server B and 75% to server C. The master server  1306   b  aggregates this server usages to produce the client&#39;s bill. 
   In order to fulfil the billing role the master server  1306   b  must log which video data the client accesses, the cost of accessing the data and the clients network address, typically their IP address. If the master server  1306   b  is to send a bill to the client via conventional mail it must retain the client&#39;s address and if it is to deduct the bill directly from an account it must retain the client&#39;s bank details. 
   Referring now to  FIG. 15 , in a second embodiment of a federated video serving arrangement a long haul data transfer arrangement  1500  comprises a building  1502  having its own Ethernet LAN  1504  that is connected to an Ethernet MAN  1506 . The MAN  1506  has a plurality of video server farms  1508   a - c , as described hereinbefore, and another Ethernet LAN  1510  connected thereto. The MAN  1506  is also connected to a long haul digital network  1512 , for example SONET, a synchronous digital hierarchy (SDH) network or a frame based fast packet-switched network typically based on asynchronous transfer mode (ATM). A second Ethernet MAN  514  is also connected to the long haul network  1512  and has a video server farm  1516  and a building Ethernet  1518  connected thereto. 
   A user  1520 , located in the building  1502  requests a video. This request is passed via the building LAN  1504  onto the MAN  1506 . The request will either be addressed to one of the farms  1508   a - c  or it will circulate about the MAN  1506  until it identifies a video farm  1508   b  which is capable of serving out the desired video. Once the request is received by the farm  1508   b  the master server within the farm  1508   b  consults the table  1400  to ascertain which server has the requested file and the available bandwidths to service the request. 
   Additionally, the table  1400  holds details of the data content stored upon servers of the other farms  1508   a,c  connected to the MAN  1506 , it may also retain the details of the data content stored on the server if the video server farm  1516 . Thus, if necessary, the request can be forwarded to the video server farm  1516  via the long haul digital network  1512  and the requested video can be served to the user  1520  using both MANs  1506 ,  1514 , the long haul digital network  1512  and thus to LAN  504 . 
   Conversely, should a user on the building Ethernet  1518  request a video that is present in one of the server farms  1508   a - c  this can be served in a manner similar to that hereinbefore described. 
   Referring now to  FIGS. 16 ,  17  and  18 , these show federated servers as described in  FIG. 13  and similar parts will be accorded similar reference numerals. As described hereinbefore the master server  1304   b  receives a request from one of the terminals  1310   c  for a video. The master server  1304   b  accesses the database  1400  to ascertain if one of the servers  1304   a - c  has the video data content upon it and if such a server  1304   a  has spare bandwidth available to stream the video to the terminal  1310   c . If the server  1304   a  has the data content thereupon but does not have the bandwidths available for streaming purposes, e.g. all streaming ports are at or near the capacity, but has bandwidth and or ports available for, for example, file transfer protocol (FTP) transactions or for RSYNC, the master server  1304   b  instructs the server  1304   a  to copy the requested data file to another server  1304   c  within the farm  1300  with available streaming capacity. 
   Alternatively, typically if there are no servers currently within the farm  1300  with ports available for streaming or no available streaming capacity the master server can connect an additional server  1304   d  to the farm  1300  and transfer the requested file to the additional server  1340   d  in order to service the request. 
   However, if subsequently demand is seen to fall significantly, the data content can be consolidated on the original servers  1304   a - c  and the additional server  1304   d  can be returned from the farm  1300  by the master server  1304   b.    
   In order to carry out a suitable method of data management upon the arrangements detailed hereinbefore it is necessary to define a data management protocol. 
   Referring now to  FIG. 19 , the master server (demand director) polls the slave servers (resource servers) periodically, typically every few seconds (Step  1900 ) in order to ascertain their bandwidth and port utilisation. The slave servers respond with details of their network address, bandwidth utilisation, the videos streamed (both currently and since the last polling), the address to which the streamed movies were sent and their price (Step  1902 ). If a server streaming data content to a user is polled for billing information the master server checks to see if it has already received the information for that particular streaming of data from a previous polling in order to prevent multiple billing occurring (Step  1903 ). 
   The master server evaluates the responses from the slave servers (Step  1904 ) and generates billing information for each user (Step  1906 ). The master server then checks to see if it is time to generate the periodic bill for the user (Step  1908 ). If it is not time to issue the bill the master server waits a set time, typically a few-days, (Step  1910 ) before again checking to see if it is time to bill. If it is time to issue the bill to the user the master server generates an aggregate bill for the user for their data access wherever upon the network it originated and issues the bill (Step  1912 ). 
   In parallel with the billing function the master server evaluates the bandwidth usage and capabilities of each of the servers, i.e. which servers have spare ports and bandwidth to output further videos (Step  1914 ). The master server determines whether the usage of each of the servers, and possibly even each of the ports of IO devices of each server, are within a predetermined limit. (Step  1916 ). If the usage is within the predetermined limit the master server returns to polling the slave servers. Alternatively or additionally each server may evaluate its own bandwidth usage and capability to serve out. 
   Should the usage fall outside of the predetermined limit the master server determines which server or servers have an appropriate port, or ports, and spare bandwidth to service the required file types and copies the most heavily used video data file to a server or server with the appropriate port and spare bandwidth (Step  1918 ). 
   Once the master server has received an acknowledgement that the data has been transferred to the appropriate slave server (content server) and has updated the database of distribution of content and network address of content servers the master server returns to polling the slave servers. 
   One command associated with such an Internet video streaming protocol (IVSP) is a “joining” command (IVSP-OP-JOIN) in which an additional server is added to a server farm. Referring to  FIG. 20  IVSP-OP-JOIN comprises connecting a video content dataserver to the network, (Step  2000 ). Once connected to the network the new video server broadcasts its data content and bandwidth available for streaming, and typically also other types of data transfer, (Step  2002 ) in order that the master server can capture them and add them to the database that retains details of which network address has which data content and available bandwidth (Step  2004 ). It is possible that servers other than the master server may also retain such tables and they too will auto-update on receiving the new video servers network address, data content and available bandwidths. 
   As server bandwidth usage increases it is necessary to compensate for this for example by starting up additional application servers software on existing video data content servers, migrating content between video data content servers or connecting new video servers to the video server farm. This requires a trigger, or alarm, command (IVSP-OP-BNDALARM). 
   IVSP-OP-BNDALARM, shown in  FIG. 21 , comprises a server monitoring either its own or another servers bandwidth utilisation (Step  2100 ). The server checks to see if the bandwidth utilisation is within a predetermined threshold limit (Step  2102 ). If the bandwidth utilisation is within the threshold limit the server waits for a period (Step  2104 ), typically a few minutes before checking the servers bandwidth utilisation again. Waiting a few minutes between checking bandwidth utilisation prevents the network and/or CPU of the servers being swamped with protocol execution and transport. 
   If this bandwidth utilisation is above the threshold limit indicating high usage, or below the threshold limit possibly indicating a problem with the server, the server sends out an alarm message to the master server (Step  2106 ). The alarm message will typically include details of the codes of videos currently being streamed from the server, the address to which they are bring streamed, the average bandwidth utilised by each movie being streamed and details of codes of videos in the server that are not being streamed. 
   The master server accesses the database and evaluates which of the other available servers within the farm is suitable and has spare bandwidth, if any, for serving the data content of the heavily utilised server (Step  2108 ). The master server facilitates the copying of the data content from to available, suitable server from the heavily utilised server (Step  2110 ). The master server thus updates the database entries relating to the suitable servers content and the address for the copied data content (Step  2112 ). 
   Referring now to  FIG. 22 , a message is sent from each server to the master server detailing their respective usages (IVSP-OP-USAGE). 
   IVSP-OP-USAGE comprises each data server self-monitoring its own input output ports traffic (Step  2200 ). These results are transmitted to the master server (Step  2202 ) which compares the results to a statistical model of network traffic (Step  2204 ) in order to determine whether or not to bring in additional data serving resources in the server farm (Step  2206 ). If there is no need to bring in additional resources the data content server returns to self-monitoring. Should the master server determine that additional data serving resource is required the resource is connected (Step  2208 ). The additional resource may be either, or both, of server application software or an additional data content server. 
   In order to produce an aggregated bill for a user it is necessary for the master server to be aware of what data content is accessed from the slave servers by the user therefore a message must be transmitted to the master server each time a user accesses the data (IVSP_OP_BILL). 
   IVSP_OP_BILL comprises the data content server receiving a request for data from a user (Step  2300 ). A message containing details of the request are transmitted, via the network, to the master server (Step  2302 ). Typically, the details contained within the message include what video has been requested, or has been streamed, the network address to which they were streamed, a user identifier and the price charged for streaming the video. 
   Each user of the video farm will have an account which is established via the network, in a manner well known in network business services. The balance of a user account is debited each time the master server receives an access message with a user identifier corresponding to that account (Step  2304 ). The user account will typically be password protected in order to prevent unauthorised access of files, for example access of 18 certificate videos by minors. 
   After one month an aggregate bill for all of the data accessed, from whatever source on the network, by a user is produced by the master server (Step  2306 ) and is sent to the user, either electronically or manually (Step  2308 ). Although shown as occurring monthly the aggregate billing can occur at any convenient interval, e.g. daily, weekly, fortnightly, etc. If a user gives their consent the master server retains their bank account details and the aggregate bill is deducted directly from their bank account (Step  2310 ). 
   There are also message relating to a request for a copy of a video to be sent to a data content server (IVSP_OP_COPY) and acknowledgement of such a request (IVSP_OP_ACK). 
   IVSP_OP_COPY request payload will typically include details of the video required, the coding format, e.g. MPEG, REAL MEDIA, encoding rates and file size. 
   IVSP_OP_ACK contains details of whether the server can service the request i.e. whether it has sufficient bandwidth available and whether the server already has a copy of the data resident upon. If the server does not already have a copy of the data resident upon the fact that it requires a copy to be sent to it in order to service the request. 
   It will be appreciated that whilst the present invention has been described with reference to video data it is equally applicable to any file based data type, for example audio data or computer based training modules, and to non-file based situations. 
   There may be a counter which is arranged to increment each time data is accessed. The farm may be part of a (Metropolitan area network) MAN. The farm may be situated in a residential building, typically a multiple occupancy dwelling (e.g. block of flats, condominium, office block). The farm may be an element in a video and/or audio rental or pay per view system. The farm may include an automatic billing unit for said rental or pay per view system. The billing unit may be arranged to generate and/or distribute bills to a user of the rental/pay per view system for content that they have accessed. 
   There now follows a description of another embodiment of the invention, with an emphasis on a monitor server monitoring the available capacity of resource servers and/or traffic levels, and varying the capacity of the network to serve out requested resource in response to the level of demand of the resource in question. The monitor server may be the same server as the demand director server referred to earlier, or it may not be. 
   It will be helpful to discuss the embodiment after a brief discussion of bow prior art networks manage demand for resources.  FIG. 24  shows a prior art network management system  2400  comprising a management console  2402  and a plurality of network elements  2404   a - e . The network element  2404   a - e  are typically PC&#39;s, servers, disc arrays, tape drives and/or printers The network elements  2404   a - e  are connected to the management console  2402  via network connections  2405   a - e . These connections need not, of course, be directly to the console  2402 —so long as the network exists. 
   The management console  2402  typically displays a network element identifier (I.D)  2406  and its status  2408 . The status display  2408  usually takes the form of a series of colour coded screen regions  2410   a - c . One of the regions  2410   a  is highlighted to indicate the status of the network element  2404   c  whose identifier  2406  is displayed. Typically a red region indicates a faulty condition such as a server failure, a yellow region indicates a warning condition, for example high network traffic and a green region indicates normal operating conditions. In an alternative embodiment the management console may display a map of the network and each network element is displayed in a colour appropriate to its operational status. 
   The above arrangement is limited in its functionality and does not remedy problems within the network as they arise: rather it alerts a person, the network administrator, to the existence of the problem. Thus, the network still requires a great deal of slow, possibly flawed, human intervention in order to remedy any fault. 
   Referring now to  FIG. 25   a , this shows a prior art shared everything clustered (SEC) server arrangement  2500  in which two servers  2502   a,b  are connected to a network  2503  via a shared network connection  2504 . Both of the servers  2502   a,b  share a common network switch  2506  that connects them to a common storage device  2508 . Any fault of the network connection  2504 , the network switch  2506 , or the storage device  2508 , renders the arrangement  2500  inoperable. This is one of the reasons that clustered server arrangements require expensive, cluster certified components. Whilst increasing fault tolerance for the servers this SEC arrangement does not increase tolerance to faults in the network, storage or switches. 
     FIG. 25   b  shows a shared nothing clustered (SNC) server arrangement  2501 ′ in which two servers  2502 ′ a,b  are connected to a network  2503 ′ via respective, independent network connections  2505 ′ a,b . Each of the servers  2502 ′ a,b  are connected to respective, independent storage devices  2507 ′ a,b  that have mirrored data contents. A link  2509 ′ between the servers  2502 ′ a,b  enables the servers  2502 ′ a,b  to monitor each others operational status. This arrangement requires expensive, cluster certified components and also there is a requirement to replicate infrastructure in this arrangement thereby increasing costs above those of the SEC server arrangements  2500  of  FIG. 25   a . Additionally, half of the infrastructure and data storage capacity may remain idle at any one time. Thus, this is a highly inefficient arrangement. 
   Referring now to the new arrangement of  FIG. 26 , a data content, or resource, server  2602  in accordance with the present invention comprises a housing  2604 , a processor  2606 , a storage device  2608  and a network interface card (NIC)  2610 . The NIC has a plurality of input/output (IO) ports  2612   a - e . Typically, the ports  2612   a - e  is configured to deliver a particular type of data content, or resource, that is stored on the storage device  2608 , for example HTTP (hytertext transfer protocol), RTSP (real time streaming protocol) or FTP (file transfer protocol), to a network  2614 . 
   The storage device  2608 , which is typically a hard disc, has an NIC monitoring programme  2609  stored upon it that is passed to, and executed by the processor  2606  when running the programme. The processor  2606  interrupts the NIC  2610  at regular intervals, typically every few seconds and samples either or both of the outgoing bitrate or/and the incoming bitrate of the NIC. (Alternatively or additionally the programme may sample metrics previously collected by the operating system). The processor  2606  compares the sampled bitrate to a reference, or threshold, bitrate stored within the programme. This reference bitrate can be varied in accordance with the type of NIC used and is typically a percentage of the ratio of the theoretical/actually deliverable bitrate capacity of the NIC. The interrupt frequency and the reference bitrate are usually set as default settings at the time of production of the program but can be altered by a network administrator. 
   Should the sampled bitrate exceed, or alternatively fall, below the threshold reference bitrate the processor  2606  executes a pre-programmed action. For example, when the server  2602  is serving video content the server  2602  is capable of serving a certain amount of such requests. The processor  2606  samples the outgoing bitrate of the NIC  2610 . As the NIC  2610  approaches its saturation level, typically 60-75% of the theoretical/actual deliverable ratio, the reference bitrate threshold is passed and the server  2602  copies the content, or resource, that is needed to serve the requested video content to a further server via the network  2614 . The content copying is executed in order to maintain the availability of the content (resource) to users who may request it as a later point in time. The processor  2606  then supplies the network address of the further server to load balancing/routing control, e.g. content-location director or tables for the network, which may be held on the server  2602  or elsewhere on the network (e.g. on a demand director server). Alternatively, or additionally, the further server may update the load balancing/routing tables, wherever they may be held. 
   It will be appreciated that the monitoring performed by monitoring programs need not be NIC usage level monitoring (or not only NIC monitoring), but could also be one or more of: local disc capacity, rate of local disc capacity growth/reduction over past set period (e.g. N seconds), NIC bandwidth growth/reduction over past set period. 
   As an even more concrete example, see  FIG. 27   a . This shows a first server  2720  having a hard disc  2722 , a processor  2724  and a NIC card  2726 , and a second server  2730  network connectable to the first server  2720  via a network  2729 , and also having similar components (which have been given similar reference numerals). Server  2720  is running load monitoring software  2709 ′ which notices when demand for a particular application  2728 , stored in server  2720  or on network attached storage (NAS) accessed by server  2720 , reaches a threshold level. If demand for the application  2728  were to rise above the threshold level the server  2720  would struggle to cope to serve out the application to meet higher levels of demand. The processor  2724  reacts to the demand for application  2728  reaching the threshold level by copying the application  2728  to server  2730 , via the network  2729 , or just starts it (the application) if the content is there already. Similarly, application software necessary to serve out a video may already reside on a server having the desired video file, in which case the application software can be brought up to serve out the video, or to reduce the load on the server&#39;s CPU if the application software is not needed at any particular time. If application software is not available on a server it may need to be telecommunicated to it. 
   In this example, the server  2720  also updates a routing, directing, or load balancing directory/database  2742  in a director server  2740  attached to network  2729  to inform the director server that application  2728  is now available on both server  2720  and server  2730 . Thus, when a request to serve out application  2728  is received by the director server  2740 , it now can choose to direct the request to server  2720  or server  2730 , depending upon which it believes can serve out the requested application satisfactorily. 
   The application  2728  could, for example, be a video performance, say purely for example the latest James Bond film. The dynamic generation of extra resource (or application) serving capacity, in real time, without human intervention, allows a network to be dynamically horizontally scaleable. That is to say, simply by attaching extra servers to the network and moving around and/or creating extra copies of requested resource/applications (which need not involve attaching extra servers), it is possible to increase the ability of the network as a whole to serve out particular resources or applications. 
   It will be appreciated that the threshold, or trigger, level of demand on server  2720  could be one or more of: a certain level of processing power capacity required; a certain level of access of telecommunications channels to serve out the application; a certain level of bandwidth availability in the telecommunications channels. Thus the application may be copied to another server (or run on a further port (logical network address) on the same server) because the processor  2724  cannot cope with too much additional demand, or because the telecommunications network relating to server  2720  is under strain (e.g. NIC and  2726  may be approaching capacity). 
   It will also be appreciated that although the above discusses copying application  2728  to another server, server  2730 , it could be copied or otherwise made available internally of the server  2720  (and any NAS linked to server  2720 ) so as to increase the capability of the server  2720  to serve out additional application  2728 . For example, application  2728  could be originally served out of only one NIC port (in the sense of part of a logical network address), but later, at increased levels of demand for application  2728 , it could be served out of two, or more, ports on the NIC of server  2720 . 
   In cases where particular applications, for example data files, are associated with a particular port  2612   a  the processor can monitor the particular port  2612   a  and copy the application data to an appropriate port on a further server, i.e. one that is configured to deliver that particular type of data, if the port on the first server is reaching saturation. 
   The server  2602  may also be configured to spawn an appropriate application programme on the further server (e.g. server  2630 ) in order to allow the copied data content to be delivered, should the further server not already be configured to deliver the data content. That is to say if the further server already has the software necessary to serve out data content that is copied to it, it is unnecessary to copy operating software, but if it does not have the requisite operating software that will have to be copied as well as the subject matter data content. 
   The processor  2606  can also compare the sampled bitrate with a lower threshold level below which it is expected that the NIC  2610  bitrate will not drop. Should the sampled bitrate fall below this lower threshold limit the processor  2606  runs a diagnostic code in order to determine if there is a fault, if  10  traffic has just decreased, or whether to use a lower serving capacity on that server. If there is a fault the diagnostic code will typically identify the likely fault source(s) and report it (them) to a system administrator. 
   It is possible, in an alternative embodiment, that the server  2602  may have more than one NIC. In this embodiment the processor can monitor one, some or all of the NIC&#39;s. Each NIC may have its own unique threshold limit or some, or all NIC threshold limits may be the same depending upon the types of NIC used. 
     FIG. 27   b  shows a server  2750  having a hard disc  2752 , a processor  2754 , a first NIC  2756  and a second NIC  2757 . An application  2758 , in this case a video movie, resides on the hard disc  2752 . Self-monitoring “capacity to serve out” software  2709 ′ is running on server  2758  to monitor when the server is likely to encounter difficulty in serving out application  2758  via original NIC  2756 . When a threshold level of demand/serving capacity is reached the software  2709 ′ causes application  2758  to be copied again in the hard drive  2752  and the copy, referenced  2758 ′, is used to serve out the same application  2758 , but via the second NIC card  2757 . Thus, the server  2750  now has a much greater capacity to serve out the resource that is application  2758  (possibly twice the capacity, or even more, depending upon the bandwidth and processing power allocated to NIC  2757 ). 
     FIG. 27   b  also illustrates the point that the disc drive  2752  does not only have the one application  2758  on it, it has others, only one of which is shown as application  2755 . In a similar manner to that described above, software  2709 ′ also monitors usage of application  2755  and if extra serving-out capacity of application  2755  is required it causes it to be copied and made available for serving out, either via an additional port on NIC  2756  or via second NIC  2757  (or both). 
   Referring now to  FIG. 28 , a server farm  2802  comprises a director unit  2804  and a plurality of servers  2806   a - e . The director unit  2804  comprises a data storage device  2808 , typically a hard disc drive, a processor  2810  and an NIC  2811 . 
   The servers  2806   a - e  comprise data storage devices  2812   a - e , typically hard disc drives, and NICs  2814   a - e . The servers  2806   a - e  are connected to a network  2816  via their NICs  2814   a - e , each NIC  2814   a - e  may have a plurality of IO ports  2817 . 
   The director unit&#39;s storage device  2808  has a monitoring programme  2818  and a load balancing/routing table  2820  stored thereupon. When executed on the processor  2810  the monitoring programme interrupts the NIC&#39;s  2814   a - e  of the servers  2806   a - e  in order to sample their outgoing bitrate. If the sampled bitrate is above a pre-determined threshold or below a different predetermined threshold the processor executes an action, as will be described in detail hereinafter. The threshold level is typically a percentage, for example 80% of the theoretical/actual deliverable bitrate for any particular NIC  2814   a . The frequency of the interrupts and the threshold levels are initially set by the vendor but are typically subsequently alterable by a user. Suitable threshold altering input devices (e.g. a keyboard) are connectable to the server, and suitable threshold-altering software resides in the server. 
   The monitoring programme  2818  is usually written in a scripted language that does not require recompilation prior to execution and constitutes a control language rather than an application language. This makes the programme  2818  flexible and powerful as it has direct implementational effect upon the system that it is intended to control. 
   The load balancing/routing table  2820  contains details of which resources or applications, e.g. portions of data, are stored on which server  2806   a - e . This arrangement is of particular importance if there is dissimilar data content distributed over the individual servers  2806   a - e  of the server farm  2802 , i.e. the data is not merely mirrored across all of the available servers  2806   a - e  of the farm  2802 : one server can have different data on it to the other servers—indeed many or all of the servers may have largely different data on them (e.g. different video movies). The table  2820  can also include an indicator of which port  2817   a  file is associated with. 
   In one more concrete example of  FIG. 28 , the network of servers  2806   a  to  2806   e  comprise a Video Farm  2830 : a collection of servers networked together and all serving out the same type of resource: video movies, and all accessible by a common input address for a resource (video) requesting party. A customer, referenced  2832 , enters the address of the Video Farm  2830  over the Internet, (represented as network  2816 ). This request is conveyed to the director unit  2804 . The director unit knows which video movies are present on which servers  2806   a  to  2806   e . The director unit knows the remaining unused resource-serving capacity of each of the servers  2806   a  to  2806   e , and it can load balance the request. Load balancing means that the director unit decides to which server to send the request for the serving out of the requested resource weighting the current availability of resource and capability of the servers to serve it out successfully, and possibly even with a knowledge of future likely resource-serving capacity of the servers. For example, the director unit may simply direct the request to the server which has the most present, current, capacity to serve out the resource—assuming of course that there is more than one server with the requested resource/video available. However, the load balancing could possibly be more sophisticated and could take into account future availability—for example if right now server  406   b  had two minutes of a movie left to play, and for server  2806   b  to accept the request to serve out a further requested movie to a new customer would take it much closer to its saturation threshold then if server  2806   c  dealt with the new request, server  2806   b  may nevertheless still be allocated the new request to serve out if in two minutes time its available capacity will rise above the level available on server  2806   c  when server  2806   b  stops serving out the movie that has newly finished. This may be attractive if server  2806   c  has a popular movie on it that is likely to be requested again soon, and it is desired to keep serving capacity of server  2806   c  available for that eventuality. 
   If there comes a time when one of the servers, say server  2806   a , gets to its threshold level of serving capacity the server  2806   a , or the director unit  2804 , causes one or more of the resources of server  2806   a  to be copied to another server, say server  2806   e , so as to increase the capability of the Video Farm as a whole to serve out the resources/video movies that are in demand. 
   Copying video movies from one server to another, or from one port to another, may of course reduce the ability of the Video Farm as a whole to serve out other, less popular, videos as the memory that contains the less popular video is overwritten with more popular video, and./or as telecoms bandwidth is preferentially allocated to, or reserved for, popular videos. 
   Thus, the capacity of the Video Farm  2830  to serve out a particular video movie is dynamically and automatically adjustable, depending upon demand. 
   Furthermore, the Video Farm can co-opt another server, not in the Video Farm at a first moment in time, but networked to or communicable with, the Video Farm. It can therefore dynamically increase its overall capacity to serve out videos (or network resources). It is horizontally scalable. This is illustrated in  FIG. 28  by server  2840 , which is connectable to the Video Farm. The director unit  2804  knows the address of server  2840 . 
   As resources, e.g. video moves, are moved around between serves the load balancing address list  2820  is updated to reflect the current addresses and capacity. 
   The director unit  2804  (or a unit that does no demand directing) can also be utilised in a fault monitoring role. For example, the director unit  2804  monitors the average data traffic within the farm  2802 . Should the average data traffic fall below a threshold, below which it should never fall, the processor  2810  runs a diagnostic code in order to determine whether a fault has occurred or whether it is just an unusual lull in network activity. As well as determining if a fault has occurred the diagnostic will usually attempt to determine the source(s) of the fault and notify a systems administrator of them. 
   In an alternative, or additional, fault monitoring role the director unit (or a monitor unit)  2804  monitors network connections  2822   a - e  to the servers  2806   a - e  and the usage of the data content of the servers  2806   a - e . This monitoring will typically be on a per-port (part of IP address) basis as each content type, for example HTTP, FTP, RTSP, typically requires an IO port (referenced as number  2817 ) to be configured for delivery of the content (this is not the same as a port upon which an application is running). For example, HTTP content is typically served on I/O port or connector  2880 , FTP on I/O port or connector  2821  and RTSP content is served on another port or connector. Typically in the case of file based data, for example, video and/or audio data, each file is associated with a particular I/O port or connector. It is possible to have multiple instances of copies of the same file being run from multiple ports or connectors on a single server. 
   The director unit  2804  retrieves the utilisation information from the respective NICs  2814   a - e  of the servers  2806   a - e . Upon noting a drop in utilisation of a network connection  2822 , possibly denoting a problem with a server or a failure of a server to respond to an interrogation signal, denoting a possible server failure, the director unit  2804  instigates a transfer of the data content that is unique to the server  2806   a  to a secondary server  2806   b  (as denoted by the arrow A in  FIG. 28 ). If the secondary server  2806   b  does not have the correct applications to service the data from the failed server  2806   a  the director unit  2804  spawns the requisite applications, subject to copyright considerations, on the secondary server  2806   b . If it is not possible to copy the data from the server  406   a  the director unit can access the data from its original source, for example a DVD, CD or tape media. The availability of the same data that is on a failed server, or the data on a server that cannot be accessed due to a telecoms failure, is assumed. A reference data store (not shown) is provided to enable the contents of the downed server to be recreated on a “live” server. 
   Once the transfer of data and applications has been completed the director unit  2804  updates the load balancing/routing table  2820  with the network address of the secondary server  2806   b  and the identity of the files, and where applicable a port identifier. 
   The director unit  2804  can also be used in high level usage monitoring, in which the director unit  2804  monitors the connections to, and usage of the content on, the servers  2806   a - e . This monitoring may be carried out on a per port basis as detailed hereinbefore. For example, if one of the servers  2806   e  is serving video data the server can only serve a certain amount of  28 . 8  Kbps video channels from any NIC. As one of the servers  2806   e  becomes busy, i.e. exceeds the predetermined threshold for its NIC  2810 , or receives more requests for a file associated with any port  2817  than it can service, the director unit  2804  co-opts an additional server  2806   f  into the farm  2802  and facilitates the copying of part of all of the data content of the busy server  2806   e  to the additional server  2806   f  (as denoted by the arrow B in  FIG. 28 ). 
   Although described as a software based implementation it will be appreciated that the ‘programme’  2818  can be implemented by any suitable hardware or firmware arrangement. 
   Referring now to  FIG. 28   a , for a server a processor monitors the traffic output via the ports of a NIC (Step  2850 ). The NIC may be part of a data content server that is associated with the processor and the processor may be monitoring the status of its own NIC. Alternatively, the processor may form part of a director unit and may be arranged to monitor an NIC associated with a server that is remote from it. 
   The processor checks to see if the network traffic on a given port, monitored at the NIC, has risen or fallen (Step  2852 ). If the processor notes a fall in the network traffic below a predetermined threshold it may issue an instruction to the NIC to shutdown a data server application on the port associated with fall in network traffic (Step  2854 ). If the processor notes a fall in network traffic across all of the ports of a NIC the processor may issue an instruction to disconnect the server from the network (Step  2856 ). 
   If the processor notes an increase in the network traffic on a given port it checks to see if there are any available ports on the NIC that are capable of serving the same format of data as the busy port (Step  2858 ). If there is an available port(s) capable of serving the format with spare bandwidth the processor starts up a data server application on the available port (Step  2860 ). The processor facilitates the copying of the data associated with the busy server&#39;s port to the available port (Step  2862 ). 
   If there are no ports available that are capable of serving the same data format as the busy port the processor issues an instruction to find a further server on the network with an available, suitable port (Step  2864 ). Once the further server has been found the processor checks the further server to see if it has the required data server application present upon the suitable port (Step  2866 ). If the suitable port does have the required data server application thereupon the processor facilitates the copying of the data associated with the busy server&#39;s port to the suitable port (Step  2868 ). The processor facilitates the data copying either by direct involvement in the copying process or by issuing an instruction to the busy server to copy the data to the further server. 
   If the further server&#39;s suitable port does not have the required data server application the processor facilitates the copying of the data server application to the suitable port (Step  2870 ), again either directly or indirectly. The processor then facilitates the copying of the data to the suitable port (Step  2872 ) as described hereinbefore. 
   After completion of the above mentioned actions associated with either a fall or a rise in network traffic a database, that contains the location of data on the network, typically as a network address and a port identifier, and the results of the monitoring of the network traffic, is updated (Step  2874 ). The table is typically used as a routing and/or load balancing table by a director class server or load balancing switch. 
   Another area of use for the present invention is in data logging. The average traffic over a network should not normally fall below a certain level. A monitor server can be set up to watch the level of network traffic and have a minimum traffic level threshold entered into it (possibly an updateable/re-settable threshold). If the threshold level is ever reached this could trigger diagnostic code, based upon that threshold, to determine whether there was a problem or not. There may be reasons why traffic will reduce without there being a system problem (e.g. Christmas Eve, Christmas Day). 
   It will be appreciated that hitherto it has not been possible to have cheap enough scalable content layer/tier of content servers, and that by allowing dissimilar content we achieve ready scalability. Being able to bring into a network new servers, with new content (content level granularity) is attractive. Furthermore, whilst rudimentary load-balancing demand directors are known, none have content and/or application awareness: they do not know what content is where and/or how busy is a server to which a request could be directed. We can add new servers for specific functionality and content can be put onto them to alleviate demands on, for instance, a server serving a particular video stream that is requested by users frequently. 
   We may well wish to provide a content-type farm (a collection of servers acting together to serve out a given resource (or application) type (e.g. video streaming 1). The farm may provide a load-balanced service. 
   Dynamically distributing content over available networked content servers so as to maximise performance of the network to serve out the content is a broad concept. A content server may be “self-aware” and migrate content when it decides to. Alternatively, a master server, or monitor server, may be “others-aware” and may decide to migrate content from other servers (it may also be “self-aware”). The monitoring may be via NIC cards/ports. Any server, e.g. a content server, may be able to monitor groups of servers of interest (and hence be a monitor server). 
   Self-aware and others-aware functionality may be used to migrate data onto servers on a network and/or to look for other problems and compensate automatically for them. For example, an “impaired” server may be impaired because it is approaching capacity and will struggle to serve out further resources, or because it has a fault, or because the telecoms links to it are faulty, or themselves struggling with capacity. Whatever the reason for the impairment to the ability of a server to serve out in the future resources in response to a request for resources available on the server, some embodiments of the invention allow these “impaired” or “missing” resources to be made available from other, less impaired, servers, so as to maintain the capability of the network as a whole to serve out the resource in question. They system may monitor for failures, or high level usage, or both. Data logging may be performed to ensure usage levels are within acceptable/usual bounds. 
   An example of failure monitoring is: a management station/director server monitors connections to a collection of servers and usage of the content on those servers (this may be on a per port basis, for example when running multiple instances of the same server application (e.g. web serving/video streaming)). When a given server or servers fails, the management station ensures that new servers are brought into play by spawning the appropriate application processes on new servers to cope with the loss and content is replicated to the new servers from its source. In order to do this, the management station or director server monitors each of the compute elements delivering a given type of content (e.g. web serving, video serving, FTP serving) and retrieves utilisation information from each of the servers, when connections to a server fail the management station/director server instigates a replication of the contents from its original source (which is assumed to be replicated elsewhere) on to the new server and starts appropriate application services on that server to enable it to serve the new content. The director then updates appropriate load balancing technology or routing tables in use to allow that new server resource to be utilised (e.g. hardware load balancing switch) and the failed server is removed from the configuration until such time as it s repaired and can be brought into play. 
   An example of high level usage monitoring is: 
   A management station/director server monitors connections to a collection of serves and usage of the content on those serves (this may be on a per port basis, for example when running multiple instances of the same server application (e.g. web serving/video streaming). When content becomes “busy” on a given server, or servers, the management station ensures that new servers are brought into play by spawning the appropriate application processes on new servers to cope with the demand and content is replicated to the new servers from its source. 
   The management station or director monitors each of the servers delivering a given type of content (e.g. web serving, video serving, FTP serving) and retrieves utilisation information from each of the servers. When connections to a server increase over a given threshold the management station/director instigates a replication of the content onto the new server and starts appropriate application services on that server to enable it to serve the new content. The director then updates appropriate load balancing technology or routing tables in use to allow that new server resource to be utilised (e.g. hardware load balancing switch). 
   It will be appreciated that a demand director/monitor server, or other processor, can evaluate whether a current level of servers and a current distribution of resources on those servers is capable of meeting expected reasonable levels of future demand, and if not to take appropriate action to increase the chance of such future demand being met satisfactorily. 
   Although in principle the network benefits of aspects of the invention can be obtained with two content servers (and a demand director or master server, with perhaps one of the content servers being a demand director and/or master server as well), there will be many times when the benefits show more clearly when there are 3, 4, 5, 6, 7, 8, 9, 10, 20, or more content servers. There may be of the order of at least half a dozen content servers. By having a large number of content servers (e.g. 6 or more), or a very large number of content servers (e.g. 10-15 or more), it is possible to have significantly different content on different servers, possibly even sub classes of content of the same general kind on different servers. (for example, it may be possible to have action movies on one server, comedy on another, science fiction on another, romantic on another, drama on another, etc.) 
   It will be appreciated that a significant advantage of many embodiments of the invention is that the level of service available on a network accurately reflects consumption of the resources. We believe that it may not be desirable to replicate data and application software services endlessly such that capacity is only ever over-provided. The amount of application serving that the collection of resource servers can provide at any one time may, in some embodiments, accurately reflect consumption of those resources by users. There may be a “low water mark” that ensures that there is never complete cessation of application serving in the event of consumers appearing, possibly suddenly appearing, not to want to resource anymore. It may well be undesirable to make the user wait until a resource can be copied and an application server brought up to service a request for that resource. It may therefore be desirable always to have at least one copy of all potentially available resources available for serving, or at least one copy of all potentially available resources present in the memory of a resource server (or accessible to the resource server), and appropriate application software for serving out any specific resource. 
     FIG. 29  shows a further example of a Video Farm  2910 . Video Farm  2910  comprising video servers  2912 ,  2914 ,  2916 ,  2918 ,  2920 ,  2922  connected in a local area network  2924 , and  FIG. 29  also shows a user  2926  connected to the network  2924  (possibly via the internet). Each video server has a number of video movies on it, say about 100 to 500 movies on each, with each movie being of about 1½ hours-2 hours direction.  FIG. 29  shows schematically each video server with  3  movies. In the case of video server  2912  they are movie V 1 , movie V 2 , and movie V 3 . In the case of video server  2914  they are movie V 4 , movie V 5 , and another copy of movie V 1 . It will be seen that some movies are present on more than one video server. Furthermore, sometimes more than one copy of a movie is present in the same video server (see video  2920  which has two copies of movie V 7 ). 
   As shown in  FIG. 30 , each video server has a central processor  3010 , a memory  3012  containing the video movies, a number of video streaming output ports  3014 ,  3016 ,  3018  or connections, a monitoring input port or connection  3020 , and a control signal output port or connection  3022 . Control software  3024  resides on the processor  3010  of each video server. 
   The control software  3024  makes each server capable of being “self-aware” and of being “others aware”, in the sense of being able to determine the performance abilities and/or characteristics of each video server in the farm  2910 . 
   This enables the video server to self manage and execute remedial actions based upon their visibility of video content usage on the network, and upon the ability of each video server to deliver video content. It also enables an individual server to contribute to managing the performance as a whole. The video farm  2910  is able to distribute video content dynamically, in response to changing conditions, over the video servers of the farm, and to bring up a new serving processes when it is determined appropriate to do so. For example, if one video server failed, e.g. server  2916 , the video farm can create extra copies of those videos that were capable of being served out from server  2916  on the other servers, so that the overall capacity of the farm to serve out videos stored upon (or accessed via) a faulty server is not significantly changed.  FIG. 29  also illustrates fault tolerance for video files: for each server having certain videos, or video items, stored on it there is another copy of each of its video items stored on at least one other server. This means that if one server is faulty, or the telecommunications lines to it are faulty, its content is still accessible from elsewhere on the farm, available to be copied/brought into service. 
   In the video farm  2910  one of the video servers, say server  2912 , takes the role of master video content servability monitor and is aware of its own operational conditions and parameters and has the operational conditions and parameters of the other servers  2914  to  2922  communicated to it via its port  3020 . 
   If for any reason the current master video server, server  2912 , is unable to perform its role properly (e.g. it develops a fault or its telecommunication links to the rest of the farm become impaired) another of the video servers can take over as the master video server. 
     FIG. 31  illustrates one of the software process that is happening on the processor  3010  of the master video server, e.g. server  2912 . 
   There are gating thresholds programmed in for performance parameters, possibly by a system manager (person) and generally they are alterable/reprogramable (a generic fixed threshold would not be able to adapt to the usage conditions experienced). In  FIG. 31  the performance parameter is to the level of usage of each video item (e.g. video movie) capable of being served out by the video farm. Usage levels for video items are checked in parallel, rather than sequentially, as illustrated. 
   The master video processor determines how many video items of each specific video item is being served out (e.g. how many video V 1   s  are being streamed out, how many video V 2   s  are being played, how many V 3   s  are being played etc). The number of video items being played currently is checked, for each video item (movie) against an evaluated known, total capacity of the farm to serve out each specific video item. It is desired to have the level of resources in the farm such that it is possible to serve out another specified number of each video item, in addition to those currently being served out. This additional, reserve capacity, number of servable video items may be the same for each video item (i.e. the farm is capable of serving out 3 more V 1   s,  3 more V 2   s,  3 more V 3   s  etc), or it may be different for at least one of the servable video items (e.g. 5 more V 1   s  in reserve, 2 more V 2   s , one more V 3 , etc). It may be desirable to have a higher reserve capacity to serve out a popular video movie than a relatively unpopular movie. For example a newly released movie may be in more demand by users and it may be appropriate to have more reserve capacity to serve out that movie than an older “classic” movie (such as Gone with the Wind). More users are likely to want to access a new release in a short time. 
   Thus upon checking the usage of video, referred  3110  in  FIG. 31 , the processor  3010  compares the actual number of videos of each specific title being served (reference  3310  in  FIG. 33 ) out with the potential capable of currently being served out (reference  3312 ) and establishes a reserve capacity  3314  to serve out video V 1  in the short-term future. This reserve capacity  3314  is compared with a maximum threshold level,  3316 , and with a minimum threshold level  3318  and the capacity of the farm to serve out extra additional copies of V 1  in the future is increased, reference  3320 , or decreased, reference  3322 , depending upon whether the minimum or maximum threshold is met or exceeded. 
   The capability of the farm  2910  to serve out a specific video V 1  can be increased by starting up appropriate video serving application software on a video server that already has the specific video V 1 , or by creating extra copies of it on the servers  2912  to  2922 , and/or making available greater telecommunications capacity for V 1 , e.g. by opening up video serving applications on ports (parts of the network address space) of the video server that were previously used for something else (e.g. voice telecomms or text communications). Similarly, capacity to serve out V 1  can be reduced, freeing up capacity to serve out other videos, by shutting down software applications that access V 1  in the memory of one or more servers and/or by overwriting or deleting V 1  in the memory of one or more servers. It is probably best as a first measure simply to disable the ability of the server to serve out V 1  (still retaining V 1  in memory of the server, e.g. in disc storage accessible by the server). This is easier to reverse in the future and often it is the processing power of a server&#39;s CPU, or the telecoms availability at its connecting ports, that restricts serving capacity rather than absolute lack of memory accessible by the server for extra copies of popular videos. 
     FIG. 32  schematically illustrates software on the processor  3010  checking other parameters which can effect the overall ability of the farm to serve out content. Boxes  3210 ,  3212 ,  3214  show the processor checking a number of different parameters (in this case 3) for each of the servers in the network (in this case 6). The parameters are checked in separate threads of execution (i.e. in parallel). Box  3216  shows a comparison of each parameter with one or more respective thresholds (e.g. parameter/with maximum threshold 1 and minimum threshold 1, and parameter 2 with maximum threshold 2 and minimum threshold 2). Box  3218  shows the processor sending out control signals in response to threshold conditions being true. The actions initiated by the control signals are preprogrammed, typically by a system administrator (person), and can typically be amended and new different actions, or new different threshold conditions can typically be input (again typically by a systems administrator). 
     FIG. 34  illustrates one parameter being monitored: bandwidth available for new users at a specific video server, say server  2922 . The master server  3022  polls each of the other servers  2914 - 2918  in the network to ask them how much bandwidth they are using. Each server runs a routine on its external network communications NIC card which monitors an appropriate parameter and reports to the master server. Thus bandwidth being used is established for each server, referenced  3410 . The potential available bandwidth to each server is known to the master server (referenced  3412 ), or to each server itself. This enables a bandwidth free for future use  FIG. 3414 , to be established. This is compared with an upper threshold  3416  and if it is above that (too much bandwidth available  3418 ) then remedial action is taken. In this case box  3420  illustrates the allocation to a video server (e.g. server  2922 ) which is adjudged to have too much free bandwidth of additional requests to serve out new videos. That is to say, in a load balancing routine controlled by the master server  2912  requests to be served a video item can be allocated to whichever video server is adjudged to have sufficient, or best, telecommunication availability. This can at least be one of the factors in deciding to which video server a request for a video is sent (assuming more than one server has the video available for serving). 
     FIG. 34  also shows a comparison  3422  of the free bandwidth available for use, for each server, with a lower threshold. If it is established that there is too little free bandwidth,  3424 , then remedial action is taken. This action could be, as shown in  3426 , the decision not to direct new requests for videos to be served out to the particular server that is getting close to its bandwidth capacity. 
   The actions  3470  and  3426  need not be as described. For example, a video actually being served out of the server that is adjudged to be too busy (too great a strain on telecommunications links) may be started up on another server, and (optionally) shut down on the busy server with an arrangement so that a user currently receiving the video from the busy server does not notice the transfer of the source of the video to the less busy server. 
   The thresholds may be adaptive, in the sense that a threshold for a specific server may go up or down depending upon what is happening elsewhere in the network. For example, whilst it may normally be undesirable to start up more videos on a server that is using 80% of its telecomms bandwidth, the master server may not have any choice if that server is the only server to have a copy of the requested video available for serving to a new user. 
   As a further example, the network may have a control database that maintains network-wide global, serving state details for each server. This may be held in the master server, or elsewhere. 
   A guide to what might be appropriate code is: 
   EXAMPLE 1 
   
       
       
         
           Database (vf0, vf, vf, vf) { 
           query (“select * from showing”)} 
           (.inactive&lt;3): ‘cool’+.titleID 
           (.inactive&gt;3): ‘heat’+.titleID 
           } every 2 seconds 
         
       
     
  
   EXAMPLE 2 
   
       
       
         
           exec (‘bandwidth vf2’) { 
           &lt;1024 k: ‘bringup vf3’ 
           &gt;2048 k: ‘mover vf2’ 
           } every 10 seconds 
           } 
         
       
     
  
   The wrapper whole database ( . . . ) { } specifies a database to run queries against, within that, queries are of the ‘exec’ or ‘query’ form. The fist example here specifies that is a title that is currently showing has more than three inactive connections, it should reduce that serving capacity for that title by calling an external process called ‘cool’ with an argument specifying which title to cool. Conversely, if there are less than three inactive connections for a given title, then more serving processes for that title should be started up, by calling an external process called ‘heat’ with an argument specifying which title needs more serving capacity from the farm. In both cases, cool and heat then run queries against serving capacity of the farm and make judgements based on appropriate serving loads on resource servers to determine where those new serving processes are started up. 
   The case of example 1 illustrates the desire that a given video title served should never have too many active processes able to serve it: hence if more than three active connections, reduce the ability to serve that title—in this case it is assumed that this would be the result of running the external process ‘cool’ with the title to cool as a specified argument (i.e. title  12  would be ‘cooled’). 
   The second case illustrates the desire to check the available bandwidth from a video server called vf2—the separate code called “bandwidth” can be run up on either the server vf2 or upon a remote server connected to vf2 via a network. When run upon vf2“bandwidth” returns the data transfer rates from vf2, typically obtained from the network card of vf2. If vf2&#39;s transfer rate is above an upper threshold value, for example 2 MB/sec, another server is brought into use in order to reduce the load on vf2. If vf2&#39;s transfer rate is below a lower threshold, for example 1 MB/sec, it will typically be allocated more content to serve as it is not fully utilising its data transfer capacity. 
   When run upon a remote server “bandwidth” samples the data transfer rate that is available from vf2. In this case if the sampled available transfer rate is below a threshold value, for example 1 MB/sec, vf2 is using a significant faction of its available data transfer capacity and therefore another serve is brought in. Conversely, if the sampled available transfer rate is above a threshold value, for example 2 MB/sec this indicates a significant fraction of vf2&#39;s data transfer capacity is unused. Therefore vf2 can be allocated more content to serve. 
   In either case, it is assumed that the external processes “bring up” or “move” will cause those events to occur. 
   All of the items within the database ( ) { } block are run in separate threads, i.e. not sequentially—so in this manner as soon as the condition become true remedial action is taken. The condition can also be set for various times. (see the ‘every N seconds’). This ensures that the monitoring process does not swamp the CPU upon which it is being executed and also that if measuring statistics, they are measured over an appropriate time period—i.e. in the case of network statistics it is not burst capacity that is being measured. 
   It will be appreciated that although  FIGS. 33 and 34  used capacity was monitored and unused capacity evaluated from that, it may be possible to monitor unused capacity directly. 
   The master server is typically aware of its own activities as a video server. If it is not actually a video server then clearly it need not know of its own serving activities/capabilities. 
   There are at least three things which can impair the ability of a video server to serve out a video to a user. Firstly, the telecommunication capability from the server&#39;s output port or connection to the user; secondly, the internal telecommunication within the server from the server&#39;s memory to its output port or connection (the video has to get from memory to I/O port); and thirdly the CPU performance (the CPU has to control, manage, and perhaps format or encode the datastream, and call it from memory). All three of these can be parameters to be monitored. We have already discussed the first. It is possible to monitor the I/O streaming performance of the disc substream (disc to I/O port)—the storage I/O performance. It is also possible to monitor CPU performance (e.g. how many of its clock cycles per second are actually being used). 
   By “memory” of the server is meant fast access chip memory, disc (non-volatile) memory inside the server, and memory attached to the server, but not necessarily physically in its housing. 
   It will be appreciated that each video server could run its own diagnostic on itself and communicate the results to the master server. Alternatively the master server could interrogate each server for their self-performed diagnostic result. Alternatively the master server could perform the diagnostic routines on the other servers. 
   When a server is completely cut off from the remainder of the network, or completely. “dead” it cannot communicate anything to the master server. The absence of information/an appropriate response to a query can itself serve as information to the master server to be acted upon. 
   Performance/capacity information may be obtained for each video item: each video movie may be evaluated as a separate thread of enquiry. 
   It will be appreciated that a demand director/load balancing server could take into account not only the question of whether a particular video server has a particular video content upon it, but also whether its telecommunications, CPU, and memory access were capable of serving out a requested video effectively, and could allocate requests with this capacity in mind. Furthermore, if it seemed appropriate to re-distribute video content over the video servers in the network this could be done automatically. For example, if a particularly busy video server had one copy of movie  101 , and only one other quieter video server had a copy of movie  101 , the master server could cause movie  101  to be copied as a precaution, e.g. from the “quieter” server, to another server so that there was an increased spare capacity to serve out movie  101 . 
   Similarly, if a specific server developed a fault and was inoperative, or could not be communicated with (fault in telecommunications) then the master server could take that into account whilst dynamically controlling the distribution of video content over the receiving servers and/or whilst allocating requests for videos to be served out to specific ones of the remaining video servers. 
   The master video server  2912  checks parameters beyond usage levels of specific video movies. 
   It is desirable to load balance telecommunications over the video farm so as to avoid bottlenecks in data transfer/video streaming. 
   Other parameters which could be monitored, and used to control overall network performance—affecting things include:
         Memory usage   Latency (response time to “pings”)   CPU utilisation   Average I/O rate per second   Other performance indicative statistics.       

   The above could be per server (and usually will be), but could also be evaluated for the network as a whole. For example, it may be possible to determine that nothing is wrong with any server but that nevertheless the network is struggling to meet demand and that more servers and/or better telecoms and/or better CPU&#39;s are needed. The remedial action may be automatic (e.g. co-opting in another server), or it may comprise the automatic generation of a report or alert to be acted upon by a human. 
   The response to monitored parameters meeting pre-programmed conditions could be based upon existing demand, or could be policy-based to take into account projected future demand. For example, greater free reserve bandwidth may be required at a time of day when it is known people like to watch video movies (e.g. 8.00 pm) and the acceptable thresholds may be adjusted, automatically or manually (e.g. by altering a program) to allow for that. The software allows programmable specification of network and serving conditions that require remedial action and the action(s) to be taken based upon those conditions becoming true. 
   The memory of a video, or resource, server typically includes non-volatile disc memory. 
   It will be appreciated that the inventions described can be used with each other, in any combination. 
   It will be appreciated that in some embodiments the invention uses a local area network, rather than a wide area network, and some embodiments involve rich media (e.g. video) farms of servers (very local servers—local to each other, often in the same room). For WAN arrangements, especially those involving the internet, and possibly involving thousands of miles of telecoms cables, the speed of light (for optical cables) can still not be fast enough to avoid issues associated with large distances between client and server, especially for time dependent consumable resources, such as streamed video files. 
   Many embodiments of the invention allow a resource (e.g. video) to be streamed out/delivered from a server using a particular application software on that server to cause the data representing the video movie to be streamed out properly. The same video may be servable out of a server using different application software, e.g. capable of handling/formatting the video data differently for different client requests. For example Real Player, Windows Media Play, and Quick Time, are three known, and different video serving application software which can operate on the same video data/file (or different video data (file) records) to serve out a video to a user/client in different protocols or formats. 
   A particular server may have the video file, or other data record of the video, in its memory, or in local attached memory. Said server may have first application software capable of serving out the video file present in local memory in the server, or in a server farm to which said server belongs, or it may not. 
   The first application software may be adapted to serve out the video file in a first way to comply with a first protocol. The first application software, when presented on the said server, may be installed on the server, or it may not actually be installed: it could simply creatable by said server using “first application installation” software that is installed on the server. Or, the application software may need to be telecommunicated to said server (or the first application installation software telecommunicated) to enable said server to have the capability of serving out the video file. 
   The first application software may be running on the said server, or it may be installed but not running: it may need to be brought up to a running condition. The first application software even when running on the server may be engaged in actually serving out the video file or it may not: it still may be capable of serving out a further video when instructed to do so. 
   Thus, to cause said server to serve out said video a migrator controller may or may not have to migrate the video file itself to the server, depending upon whether the server already has a video file available or use in serving out the video. The first application software, necessary to serve out the video in the first way, may need to be migrated to said server, or it may not, depending upon whether it already exists and whether, this currently fully utilised in serving out video. 
   The first application software may need to be installed if it already exists on the server, or it may not, depending upon whether there is already installed first application software free for use (not otherwise occupied). Or first application installation software may or may not need to be migrated to the said server, depending upon whether it already exists on the server in a useable form. 
   An instruction to said first server to install the first application software may need to be transmitted to said server. 
   An instruction to run installed first application software may need to be transmitted to the said server. 
   Similar points apply to second, and further, application software capable of serving out the video file in second, and further, ways that comply with second, and subsequent protocols. 
   Which of a plurality of video-serving application software it is necessary to have running on the server to satisfy a request for the video depends upon the format of the video requested by the client. 
   Just as different data software/software may or may not need to be transmitted to a server to enable it to serve out an additional video at any particular time, when a specific server stops serving out a video in a particular format it may be appropriate to bring down the running of a specific video serving application software in order to reduce demand on the processing unit of the server. This may involve leaving the application software installed, but not running, or de-installing it. Usually the application-installation software would be left on the server, but it might also be de-installed. Usually the video file would be left on the server, but it also might be de-installed/removed from memory there. 
   Many embodiments of the invention determine whether it is necessary to transmit to a selected server that is to serve out a specific video in response to a specific demand for the video by a client the particular kind of video serving application software necessary to serve the video out in a way that will meet the demanded format, and will migrate/transmit to the selected server the minimum data/software necessary for it to achieve the serving out of the requested video into the requested format (i.e. they will not automatically transmit to the server everything it might conceivably need (application software and video file), just what it does not already have free for use, or that it cannot create itself). This tailoring of the migrated software and data to the specific needs (present or future) of the server reduces the utilisation of bandwidth in the migration process, leaving more bandwidth free for the actual satisfying of client requests for videos. 
   Also, in a system where the resources that are servable out are of different kinds (e.g. different kinds of video formats, and/or web pages, and/or audio only media, and/or other rich media), there may be other serving out application software necessary to serve out the actual data representative of those different kinds of resources. 
   In determining which servers are capable of satisfying a particular demand a demand server has to establish what application software it is necessary to have running on the chosen resource server, and that the selected resource server not only has access to the data contact of the resource to the served out but also to the appropriate serving-out application software necessary to serve the data out in the required way. 
   It will be appreciated that a signal from a demand director to use video serving application software that is already running on a video server to serve out a particular video title, and a signal to bring up to a running condition installed video serving application software, or to use application-installing software to install and run a video serving application, has fewer bits in it than actually transmitting a video serving application-installing software to a server, which in turn has fewer bits than actually transmitting video serving application software itself to the server, which in turn has fewer bits than transmitting a video file data record itself. 
   When moving data around a farm, or local area network, or indeed around a wide area network, many embodiments of the invention assess the need to move video data records, e.g. files, (for example), or whether it is possible to move something that has fewer bits. For example migrating or copying a particular video-serving application software program to a specific server that already has video data ready for serving may enable that specific server to serve out an additional copy of that video. This may consume less network resource than automatically, without consideration, migrating the desired video file and the necessary application software to serve it out in a specific format. 
   Similarly, migrating or copying video-serving application installation software, a condensed packaged software program which can be used by the recipient server to create the required format/protocol of video serving software, can reduce the network resources consumed in enabling a new server to have the capacity to run video serving application software of the desired format/protocol. This may be done in advance, before there is an actual demand for a video (or other rich media or other resource) to be served out, so as to maintain capacity to respond to a future request to serve out video in that format/protocol. For example, if a particular video server has a plurality of unused video serving application software of a first format/protocol running or installed, but no unused video serving application software of a second, different, kind of format/protocol, running or installed it may be desirable to have that server run or install an appropriate software program of the second format in place of one of the application software programs of the first format (so that there is reserve capacity of video serving application software of both formats on the video server). 
   The second format of video serving application software may be copied, installed or brought up running from within the server in question, or it may be migrated to the server in question from another server. Distributing ready-for-use, unallocated, running or installed (or installation) video serving application software over a farm, or local area network, or of video servers, without necessarily migrating video files themselves, in order to be ready to serve out videos from the servers in a variety of formats/protocols is what is achieved by some embodiments of the invention.