Patent Publication Number: US-8126986-B2

Title: Advanced content and data distribution techniques

Description:
RELATED APPLICATION 
     The present application claims priority as a divisional of U.S. patent application Ser. No. 10/949,993, entitled “ADVANCED CONTENT AND DATA DISTRIBUTION TECHNIQUES” filed on Sep. 23, 2004, which is incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the field of content precaching in a networked environment; more particularly, the present invention relates to filtering a set of content objects in a web environment to match the resources of the client that is going to use the objects. 
     BACKGROUND OF THE INVENTION 
     The World Wide Web (“web”) uses the client-server model to communicate information between clients and servers. Web servers are coupled to the Internet and respond to document requests from web clients. Web clients (e.g., web “browsers” are programs that allow a user to simply access web documents located on web servers. 
     An example of a client-server system interconnected through the Internet may include a remote server system interconnected through the Internet to a client system. The client system may include conventional components such as a processor, a memory (e.g., RAM), a bus which coupled the processor and memory, a mass storage device (e.g., a magnetic hard disk or an optical storage disk) coupled to the processor and memory through an I/O controller and a network interface, such as a conventional modem. The server system also may include conventional components such as a processor, memory (e.g., RAM), a bus which coupled the processor and memory, a mass storage device (e.g., a magnetic or optical disk) coupled to the processor and memory through an I/O controller and a network interface, such as a conventional modem. 
     To define the addresses of resources on the Internet, Uniform Resource Locator (URL) system are used. A URL is a descriptor that specifically defines a type of Internet resource and its location. To access an initial web document, the user enters the URL for a web document into a web browser program. Then, a request is made by a client system, such as a router or other network device, and is sent out over the network to a web server. Thus, the web browser sends a request to the server that has the web document using the URL. The web server responds to the request and sends the desired content back over the network to the requester. For example, the web server responds to the HyperText Transfer Protocol (HTTP) request by sending the requested object to the client. In many cases, the object is a plain text (ASCII) document containing text (in ASCII) that is written in HyperText Markup Language (HTML); however, the object may be a video clip, movie or other bandwidth intensive content. 
     A problem with the Internet is that it has limited bandwidth resources and different points in the Internet may experience network congestion, resulting in poor performance especially for bandwidth-intensive applications. The Internet backbone is often painfully slow. The bandwidth limitation is mainly due to one or more congested links between the web server and the client. Broadband access can help in solving the first mile problem but does not help if the congestion occurs deeper in the network. The “first-mile” is the first link from the server to the Internet. This can become a bottleneck if the content provider does not provision for sufficient bandwidth on this link or if there is a “flash-flood” of requests to the server. 
     One prior art solution to accommodate the slowness of the Internet backbone is to move content closer to individuals desiring the content. To that end, content may be cached on the carrier edge and requests for such content may be serviced from these caches, instead of the web server servicing the requests. Distributing content in this manner can require large numbers of cache memories being deployed at the carrier edge and each cache memory stores content from a number of sites. When a request is made for content from a site that has been stored in one (or more) of the cache memories that is closer (from a network proximity viewpoint) to the requester than the original website, the request is satisfied from the cache. In such a situation, the interactive experience for text and images is improved significantly only if content from the site has been stored in the cache and the individual making the request is close enough to one of the servers supporting such a cache to satisfy requests with the content stored therein. This is referred to as carrier edge caching. One provider of such a service is Akamai. Also, such an arrangement for caching content requires that the content owner and the entity caching the content enter an agreement with respect to the access for that content so that the content can be stored ahead of time. Some of the providers of a carrier edge caching service use dedicated links (e.g., via satellites) to feed web pages and embedded objects to these servers and circumvent the Internet backbone entirely. Providing carrier edge caching for high resolution video requires a particularly large number of servers to be deployed, since the number of clients each server can handle simultaneously is very small. 
     While carrier edge caching takes the load off the backbone and has the potential to significantly improve the end user&#39;s experience for text and image-based content, there are two major shortcomings with this approach. First, it requires hardware infrastructure to be deployed on a giant scale. Without servers in all major ISP&#39;s point of presence (POPs) and satellite receivers in central offices (COs), caching on the carrier edge does not work effectively. To deploy and maintain this hardware infrastructure is very cost intensive. Second, the last mile access link remains the bottleneck for affordable truly high resolution video for the foreseeable future. 
     While carrier edge caching has shortcomings, there are other problems associated with providing content over the Internet. For example, when providing content over the Internet, a content provider is limited in only being able to display the content in one way and without any insight into what content is already cached at a particular client. In other words, the content provider is limited in that it does not know what client side caching is occurring. This may limit a content provider&#39;s ability to control the number and order in which those content objects are displayed as that is under the control of the browser. This is of significance when the content provider only desires to allow display of content to which an individual has subscribed. 
     Another limitation on the content provider is that they cannot provide different sets of content objects to match different clients having different resources. In other words, a content provider cannot determine the resources that a client requesting content has before sending content objects to the client to tailor the set of content object for the particular client. This causes the content provider to provide the same set of content objects to all clients where the content objects are selected based on the likelihood that the majority of clients will be able to display the content objects, which is not near optimal. 
     SUMMARY OF THE INVENTION 
     A method and apparatus for displaying locally stored content objects is disclosed. In one embodiment, the method comprises receiving a message containing one or more parameters indicative of one or more characteristics of a client, and sending one of multiple groups of one or more content objects from a set of content objects to the client based on the one or more parameters. Each of the groups is suited for use with clients having a different set of one or more parameters. 
     Other features and advantages of the present invention will be apparent from the accompanying drawings and from the detailed description that follows below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be understood more fully from the detailed description given below and from the accompanying drawings of various embodiments of the invention, which, however, should not be taken to limit the invention to the specific embodiments, but are for explanation and understanding only. 
         FIG. 1A  illustrates a flow diagram of one embodiment of a process for controlling the display of documents. 
         FIG. 1B  is a flow diagram of one embodiment of a process for providing content objects to a client. 
         FIGS. 2 ,  3 ,  4 , and  5  illustrate embodiments of a precaching architecture. 
         FIG. 6  is an exemplary protocol to facilitate precaching. 
         FIG. 7  is a block diagram of one embodiment of a computer system. 
     
    
    
     DETAILED DESCRIPTION 
     A method and apparatus for integrating the display of locally stored content objects into web pages is described. In one embodiment, the method comprises receiving a message containing one or more parameters indicative of one or more characteristics of a client, and sending one of multiple groups of one or more content objects from a set of content objects to the client based on the one or more parameters. Each of the groups is suited for use with clients having a different set of one or more parameters. In one embodiment, the objects are part of a web page and a browser receives the page over a network. In one embodiment, the page includes a program (e.g., script) and one or more links to objects that are accessible over the network. The client obtains a list of one or more locally stored objects based on information in the script. The client stores these objects, The client then is able to display a web page using one or more locally stored objects. 
     The content objects may include web pages, video files, audio files, source code, executable code, programs (e.g., games), archives of one or more of these types of objects, databases, etc. A chapter, for purposes herein, is a set of content objects classified according to content. 
     In the following description, numerous details are set forth. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form, rather than in detail, in order to avoid obscuring the present invention. 
     Some portions of the detailed descriptions that follow are presented in terms of algorithms and symbolic representations of operations on data bits within a computer memory. These algorithmic descriptions and representations are the means used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. An algorithm is here, and generally, conceived to be a self-consistent sequence of steps leading to a desired result. The steps are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical, magnetic, or optical signals capable of being stored, transferred, combined, compared, and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like. 
     It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the following discussion, it is appreciated that throughout the description, discussions utilizing terms such as “processing” or “computing” or “calculating” or “determining” or “displaying” or the like, refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system&#39;s registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices. 
     The present invention also relates to apparatus for performing the operations herein. This apparatus may be specially constructed for the required purposes, or it may comprise a general-purpose computer selectively activated or reconfigured by a computer program stored in the computer. Such a computer program may be stored in a computer readable storage medium. A machine-readable medium includes any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computer). For example, a machine-readable medium includes read only memory (“ROM”); random access memory (“RAM”); magnetic disk storage media; optical storage media; flash memory devices; electrical, optical, acoustical or other form of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.); etc. Each may be coupled to a computer system bus. 
     The algorithms and displays presented herein are not inherently related to any particular computer or other apparatus. Various general-purpose systems may be used with programs in accordance with the teachings herein, or it may prove convenient to construct more specialized apparatus to perform the required method steps. The required structure for a variety of these systems will appear from the description below. In addition, the present invention is not described with reference to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement the teachings of the invention as described herein. 
     Overview 
     A method and apparatus for integrating the display of locally stored content objects into web pages is described.  FIG. 1A  is a flow diagram illustrating one embodiment of a process for manipulating content objects. The process may be performed by processing logic that may comprise hardware (e.g., circuitry, dedicated logic, etc.), software (such as is run on a general purpose computer system or a dedicated machine), or a combination of both. 
     Referring to  FIG. 1A , the process comprises processing logic (e.g., a client, a browser) receiving a web page over a network connection (processing block  101 ). The page includes a program (e.g., script) and one or more links to content objects that are accessible over the network. As described in more detail below, in one embodiment, the content object may come from a content provider or another peer. 
     Processing logic, such as a web browser, prior to allowing the page to be displayed, obtains a list of one or more locally stored objects from a process running on the same machine as the web browser (e.g., a daemon process, called “agent”) (e.g., script) (processing block  102 ). 
     Thereafter, processing logic (e.g., the web browser) displays the page with links to zero, one or more locally stored content objects (processing block  103 ). 
     In one embodiment, a web browser running on the client changes the link to a content object after determining that a client has downloaded or is in the process of downloading this content object (or one or more additional objects) or portions thereof, such that these content objects are in the cache of the client. A daemon process or agent also running on the client provides this information to the browser. For example, the agent may provide information to a program (e.g., script) in an HTML document that causes a web page to be displayed in a certain fashion (e.g., only showing content objects already in the client&#39;s cache or only those subscribed to). In another example, such information may cause the web browser to embed an object in another page to display a content object to an individual. 
     In one embodiment, a web browser on the client changes a web page by replacing at least one string in the page based on the information provided by an agent running locally to the client. The string may be a portion of a program (e.g., script). In one embodiment, the web page includes a program that uses the information to indicate how a content object is to be presented or stored at the client and changing the web page comprises modifying the program to change a representation of the content object. The local information upon which a change in the web page is based may be whether an individual is subscribed to one or more other objects and/or whether one or more other objects are stored in a cache of the client. 
     Changing web pages by replacing strings in the page to indicate how a content object is to be presented or stored at the client is described in U.S. patent Ser. No. 10/194,623, entitled “Web-integrated Display of Locally Stored Content Objects,” filed Jul. 11, 2002, and assigned to the corporate assignee of the present invention. 
     In one embodiment, the content objects in the web page may be different for different clients. In such a case, the different sets of objects are filtered based on client resources such as a client with more and/or better resources gets a set of content objects that takes advantage of those resources, while a client without those resources would get a different set of resources. This is described in greater detail below. 
     One Embodiment of an Architecture for Content Precaching 
     The teachings described herein may be utilized in a networked environment that supports content precaching.  FIG. 2  illustrates one exemplary embodiment of an architecture for content precaching. Referring to  FIG. 2 , one or more content providers (e.g., web servers, video servers, audio servers, etc.)  202  are coupled to the Internet  206  or another networked environment. One or more clients  203  is coupled directly to Internet  206 , or indirectly coupled to Internet  206  through a client appliance  205 . 
     Clients  203  or  204  may comprise a PC, a work station, a network appliance device, a web pad, a wireless phone or other communication device, a set-top box, etc. Client appliance  205  may be implemented on a service gateway (e.g., a router, bridge, switch, other network device) in the LAN or as an end point on the LAN. Clients  203  or client appliance  205  may run software and reside in a LAN or other networked environment. In one embodiment, the precache memory is part of client  203 . In another embodiment, the precache memory is part of client appliance  205 , or on another client machine that is linked to client  203  by way of a LAN or some other networking subsystem. 
     Client  203  or client appliance  205  may be coupled to the Internet by a modem link, a digital subscriber line (DSL), cable modem, (fixed) wireless connection, fiber, etc. This coupling may be either a direct connection, or indirectly connected through a router, switch, or other similar device. 
     One or more clients may be peers. A peer is a “nearby” or local host, such as, for example, a host in the same LAN, a host connected to the same ISP, or any other networked device offering reasonable connectivity (e.g., bandwidth, latency). In  FIG. 2 , any or all of clients  203  or client appliances  205  may be in peer relationships with each other. 
     Master controller  201  is coupled to Internet  206  or some other networked environment. In one embodiment, master controller  201  is a server host or cluster of server hosts along with storage (e.g., network-attached storage, database engines), and typically resides in a controlled environment at one or a few locations strategically placed in the Internet to allow for reasonable connectivity. 
     In one embodiment, the precaching described herein involves building a user profile, subscribing for update notifications for new content (e.g., objects) based on information in the user profile, downloading the new content, and intercepting user&#39;s requests for a web server to transparently return the content to the user. As described in more detail below, a user profile may be built by tracking user access patterns, receiving profile information from another entity, and/or being configured with a profile (or portion thereof) from a user. 
     A client may subscribe for an update of new content based on information in the user profile. In one embodiment, periodic checking is performed to obtain an update of new content and includes sending the requests to the controller, which determines if there are any new content objects that correspond to content specified in the profile. A determination of whether new content exists may be performed by querying a master controller, subscribing with the master controller, and/or crawling the networked environment. Each of these will be described in more detail below. 
     In one embodiment, to facilitate the precaching process, the master controller maintains one or more databases of available objects and the locations of the objects. As new content becomes available, the controller searches the database of client profiles to determine the set of clients that will want a copy of the new content. The controller sends a message to each of the clients in the set to instruct them to download the content. The message contains the location from where an object may be downloaded to the client making the request. When the content has already been downloaded by a peer client, the controller may indicate to the other clients making the request that the peer client has the content and provides an indication to allow the requesting client to download the content from the peer client. Thus, in such a case, there is peer-to-peer precaching. 
     In an alternative embodiment, the controller checks for new content, in response to a request by a client, by searching one or more database(s) to determine if the content object has been already downloaded by a client in the system. 
     In one embodiment, the clients run on a platform and maintain profiles. A client may be an end point of a network or one or multiple hops away from the end point of a network (e.g., a local area network). By forwarding its profile to the controller and having the controller indicate when to download new content objects, the client is able to obtain and precache content objects prior to web browser or other end user program requests based on profiles. The content objects are downloaded and stored in a precache memory (or disk) when the network access link is not being used interactively. 
     When a web browser or other end user program makes a request for a content object, the client intercepts the request and checks to determine if it has the content object stored locally. If it is stored locally, then the client obtains the content and sends the content object to the browser or other end-user program using any inter-process communication (IPC) mechanism; in doing so, the object may simply be transferred to another task, process, or thread running on the same machine as the client, or it may travel over a local network (e.g., LAN) to a different machine that is running the browser or end-user program. If the content object is not available locally, then the client retrieves the object, or a low-quality representation of the object, over the wide area network from any server which hosts the content object. 
     Thus, each of the clients sends a profile to the master controller (NOC). The master controller gathers information about new objects being published and compares this to the profiles of each client to determine which objects the client&#39;s should download. The information of more objects being published may come from content servers. In other words, the master controller indicates to the client(s) when to download specific objects (and when to delete content). The master controller provides this indication in the form of commands. In other words, after downloading, each client has a collection of cached objects residing on disk, which is managed by the master controller. 
     Discovery of Content 
     Master controller  201  can discover content that becomes available at content servers  202 . One way in which new content can be discovered is through direct reports  210  coming from content servers  202 . Such direct reports  210  could be generated periodically, or in response to an event on server  202  (e.g., new content being placed on the server by the server administrator). Direct reports  210  are usually generated by software running on servers  202 . 
     Another way in which master controller  201  can discover the availability of content on content servers  202  is by use of a server appliance  207  that is co-located on the server  202 &#39;s site, or close to it. Server appliance  207  can locally crawl ( 220 ) through the content on server  202  frequently to check for the availability of new content. It can then report new changes, or provide a summary of all content on server  202 , by sending messages  230  to master controller  201 . In this context, the server  202  need not run any special software that can communicate directly with the master controller. 
     A third way in which master controller  201  can discover the availability of content on content servers  202  is by directly crawling ( 240 ) the content available on content server  202 . This crawling operation  240  is similar to the way in which web search engines retrieve files from an Internet web server. 
       FIG. 3  is an alternative view of  FIG. 2  illustrating the gathering of profiles. Referring to  FIG. 3 , clients  303  maintains profiles for local users. In one embodiment, the profile is built based on observing user access patterns, and from those access patterns, determining what types of content the end user will want to access in the future. In another embodiment, the profile may be built up or augmented by information provided directly by the master controller  301  or the end users or both. A local network administrator may also add to the profile. 
     Profiles for one or more clients  304  may also be maintained by a client appliance  305 . In this case, it would not be necessary for clients  304  to run special software to collect and report profiles. 
     Clients  303  report on the profiles they maintain to master controller  301  using messages  310 . Similarly, client appliances  305  report on the profiles they maintain to master controller  301  using messages  320 . Messages  310  and  320  can be generated periodically, or in response to some event (e.g., a request from master controller  301 ). 
       FIG. 4  is an alternative view of  FIG. 2  illustrating the initiating of downloads directly from the server. Referring to  FIG. 4 , master controller  401  uses its knowledge of what content is available on content servers (as described in  FIG. 2 ), and its knowledge of client profiles for different clients  403  and  404 , to initiate downloads of content that will likely be needed in the future at clients  403  and  404 . Master controller  401  sends messages  410  to clients  403  and client appliances  405  which contain commands to initiate downloads of content data from locations  402  specified in the messages  410 . Clients  403  then send a message  420  to the content server  402  from which the content is to be downloaded. Content servers  402  then respond to these download requests  420  by returning the content data  430  to clients  403 . Client appliances  405  retrieve content data from servers  402  in a similar manner. 
       FIG. 5  is an alternative view of  FIG. 2  illustrating initiating downloads from peers. Referring to  FIG. 5 , master controller  501  uses its knowledge of which clients  503  and client appliances  505  have already downloaded specific content objects to initiate downloads of content directly from a peer client. In one embodiment, master controller  501  sends a message  510  to client  503 . 1  to initiate download of a content object from peer client  503 . 2 . Client  503 . 1  sends a message  520  to peer client  503 . 2  to retrieve the specified content. Client  503 . 2  then acts as a content server by responding to request  520  by sending the specified content data  530  directly back to client  503 . 1 . In another embodiment, master controller  501  can send a command to a client to upload a specified content object to a specified peer client; this is useful when the client sending the content data cannot be directly contacted by the requesting client, perhaps because it resides behind a firewall. Client appliances  505  can get content from peer clients  503  and/or other client appliances in a similar manner. 
     In an alternate embodiment, clients  503  or client appliance  505  may directly query the master controller  501  for new content objects that match their local profiles, and receive from the master controller  501  a list of the new objects that are available, as well as their locations (e.g., content servers  502 , peer clients  503 , or peer client appliances  505 ). These queries may occur periodically or in response to some external event (e.g., a request from the master controller). Clients  503  or client appliances  505  can then select a suitable location to directly download the content from. In this embodiment, master controller  501  need not maintain profiles for all the clients, and messages  310  and  320  would be unnecessary. 
     In one embodiment, master controller  501  knows four things: 1) the content clients want based on profiles received from clients; 2) the new content that is available; 3) the location of the new content (e.g., servers, carrier edge caches, peers, etc.); and 4) network information such as, for example, network connectivity (e.g., network topology information, bandwidth, delay, and dynamically changing snapshots of network congestion and/or utilization). Using this information, master controller  501  schedules downloads of new content objects to clients  503  and client appliances  505 . Such downloads may take the form of commands such as, for example, “get object from server 1” or may take the form of instructions such as, for example, “instruct client 2 to obtain the object from client 1.” The network information and information about which downloads are taking place allow master controller  501  to do provisioning taking into account resource availability. 
     In one embodiment, master controller  501  is able to coordinate downloads so that prior to a download of content completing to a particular client, another download of that content may start occurring form that particular client. This kind of pipelining of downloads can significantly reduce the delay before a content object is replicated to a potentially very large number of clients and/or client appliances. 
     Clients  503  download content objects from the locations specified in messages  410  or  510  from the master controller. For example, in one embodiment, client  503  may download bandwidth intensive content such as, for example, movies, video, software, images, sound files, etc. Client  503  stores the content locally in one or more precache memories. The precache memory may be part of a client  503  (or is at least accessible by it over a fast link, for example, over a LAN). The content may be downloaded on the end user&#39;s premises. In one embodiment, the downloading occurs without excessive interference with any other interactive network traffic. 
     A user request may be generated (e.g., from a web browser) to download specific content from the network. Client software running on an end system can observe these requests. Alternately, a client appliance can observe such a request originating from an end system to which it is connected (e.g., through a LAN). Clients or client appliances monitoring these requests can detect when the request is for a content object that is in the local precache memory of the client or client appliance. If such a request occurs, clients or client appliances can satisfy the request by returning the stored (precached) content object from its local precache memory. If the request is for a content object that is not in the precache memory clients or client appliances can forward the request on to their original destination (e.g., content server, carrier-edge cache, etc.). Thus, requests for a specific type of bandwidth intensive content are intercepted. In one embodiment, clients and client appliances are configurable to intercept requests for a certain type of content object. 
     Thus, with content cached locally, clients and client appliances detect requests for embedded objects, check their precache memory to determine if the embedded objects are stored locally, and return the object from the precache memory if available. If the content is not available, the request is sent out into the network (e.g., Internet) to an appropriate location where the content or an alternate representation of the content may be found. 
     Client-Specific Filtering 
     In one embodiment, to compensate for different users having different computer systems with different capabilities, the NOC is able to target systems that have better hardware and/or software with better quality content. In such cases, those users having less hardware and/or software resources are sent lower quality content. Such functionality is performed by the system manager or other back-end software representing the NOC. In one embodiment, the NOC is a server running software. 
     In one embodiment, the provider publishes objects into different channels, or chapters, and different clients subscribe to different channels. The provider publishes an object&#39;s description into individual channels. Thus, there is a list of object descriptions for each channel. 
     In one embodiment, to selectively target users based on client (machine) characteristics, the client machines send the characteristics and/or parameters when they connect to the NOC or change one or more of those characteristics or parameters. Such parameters may include, but are not limited to, CPU type (e.g., Pentium, Atalon), CPU speed (MHz), memory (megabytes, physical memory size), video card name, video card memory (Ram), operating system, the set of installed application programs (RealPlayer, Windows Player), network bandwidth, and type of network connectivity (modem, cable, T1, etc.) 
     In one embodiment, the process to implement the providing of higher quality content requiring better resources is performed by the NOC.  FIG. 1B  is a flow diagram of one embodiment of a process for providing content objects to a client. The process is performed by processing logic that may comprise hardware (e.g., circuitry, dedicated logic, etc.), software (such as is run on a general purpose computer system or a dedicated machine), or a combination of both. 
     Referring to  FIG. 1B , in one embodiment, the process comprises the NOC receiving a message from a client when the client first connects to the NOC that indicates parameters and/or characteristics of resources of the client (processing block  121 ). Note that the NOC keeps the information provided by the client and does not forward such information to the provider. In one embodiment, the information is maintained by the NOC as long as the client remains connected to the NOC. In other words, the information is maintained by the NOC for the period of one connection. Alternatively, the NOC may save the information. The information may be maintained in the database. 
     Then, in response to receiving the message from the client indicating its capability, the NOC provides the content that is best suited for the resources of the client (processing block  122 ). In other words, the NOC provides content objects selected based on the resources of the client. The NOC sends instructions to the client to make it download certain content objects, which match its hardware and software configuration. 
     In one embodiment, in order to determine which content is best suited for the individual client, the NOC utilizes filters provided by the content provider. In one embodiment, each channel includes an ordered list of objects, which are typically delivered in order to a client that subscribes to the channel. However, the channel also includes one or more filter specifications that specify ranges of values of hardware and software characteristics, such as, for example, CPU speed. In one embodiment, the filter specification defines machine requirements that are necessary in order for a client to view the content at its best quality. For example, a filter specification may be the following: 
     If CPU is Pentium with &gt;500 MHz and &lt;1 GHz and has a video card with &gt;16 MB of Ram. 
     In one embodiment, each channel has one or more types of filters such that each channel is an ordered list of filters with an associate list of objects for each filter. In one embodiment, each channel includes one or more filters followed by the object that is associated with the filter, as well as a default filter if the filter specification associated with the earlier filters in the channel does not apply to the particular client device being supplied subscribing to the channel. 
     When providing content, the NOC determines what parameters the client has indicated when connecting to the NOC in terms of whether they match the first filter. If the resource list provided by the client matches the first filter, the NOC makes the client download the object associated with that filter. If not, the NOC goes to the next filter and determines whether the client&#39;s resource list satisfies the filter specification of the second filter. If so, the NOC provides the object list associated with that filter. If the resources of the client meet none of the specifications of the filters for the channel, the NOC provides the default object list to the client (i.e., the objects associated with the default filter). 
     This may be alternatively viewed as classifying each client&#39;s system into different classes based on their available resources. In one embodiment, each type of filter is given a name. In such a case, each client&#39;s systems may be associated with particular filter names. By naming a particular filter, a provider may utilize the same name of the filter over multiple channels. Thus, the filters define the class and there is an object list for each class. 
     In one embodiment, the parameters and/or characteristics of the resources of the client are only those that do not change over the life of a single connection. Alternatively, parameters that do change over the life of a connection are included in the resource indication provided by the client. In such a case, the client sends a subsequent message to the NOC to indicate a change in one or more of its parameters. For example, measured network bandwidth may change over time for a particular client. When a change does occur, the client sends a message to the NOC to notify the change. 
     By providing the filtering described above, multiple users subscribed to the same channel may have different end user experiences, each optimized for the resources that are available on the client machine. 
     Versioning 
     In one embodiment, a channel contains certain content and is published by a content provider with one or more objects. These objects are delivered to all subscribed clients. However, at a later time, the content provider may decide that they want to update a particular object with new information or make changes to correct to an object (e.g., to correct a mistake in an object). In one embodiment, the content provider may specify a newer version of the object and have the newer version sent to clients that already have the older version of the object. Newer clients that subscribe to the channel after the newer version is available would get only the newer version and never have access to the older version. 
     In one embodiment, clients that currently have the older version would continue to be able to use the older version until the newer version is completely available (downloaded). In other words, the older version is not deleted until the newer version is available on the client machine. Alternatively, as soon as a newer version is made available by the content provider, a message may be sent to the client to disable the older version. 
     In one embodiment, such versioning may be used for fixing or replacing bad or outdated objects or adapting an object over time based on external factors. Note that this may be done transparently to the application. 
     In one embodiment, the provider adds a newer version to the. top of the. object list. The NOC chooses the topmost object (the latest object) to download to a particular client. While the client machine is downloading a newer version of an object, the older version is used, and only switches after the download has been completed and a check is made to see if the object is proper. In one embodiment, the check is performed by computing a checksum, such as a one-way hash (e.g. SHA1). 
     Note that in one embodiment, all the objects have the same name and a version number is used to distinguish between older and newer versions. In one embodiment, it is important that the name of the object not change. By maintaining the same name for newer and older versions of the same object, web pages that specify the name of an object to appear in a web page, need not be changed every time a different version of an object is created. 
     In one embodiment, if the downloads of an older version and a newer version overlap, there are two alternatives that may be implemented. In one embodiment, the download of both continues. Alternatively, the download of the older version is stopped while the latest version continues to be downloaded. 
     In one embodiment, objects consist of a number of files. Such objects are referred to herein as packages. If a newer version of such an object is made available, yet only one or more files have changed, it would be desirable to only change those files and not have to download an entirely new package. In one embodiment, a package includes an index to the files. The index indicates all file names, file lengths, and checksums. When a newer version is published of the same object, the NOC tells the client to download the new version of the object. The NOC downloads a table of contents of the newer version of the object and compares the checksum of the files in the newer version with those of the older versions. The NOC then only causes the new files in the package to be downloaded. In one embodiment, the NOC specifies the byte range of the new object it needs and when the client gets them it incorporates them in the package. Thus, the client then only gets those new or different portions of the package it needs. 
     Alternatively, the client determines which files are new, and which files have been deleted, and only downloads those portions of the new files it needs. 
     X-Delta 
     In one embodiment, the architecture of the network resembles a distributed web server where each client has a directory tree that is the same as the directory tree of a web server. Thus, the contents of a web server are distributed over all the clients. Clients download everything in the directory tree and have their own copy of the directory tree. The directory tree itself consists of one or more files that are published by the content provider. 
     In one embodiment, the client only downloads the changes to the directory tree consisting of one or more files. In one embodiment, this is done by creating a package consisting of the directory and publishing the package that is described above. Alternatively, the content provider indicates changes to the directory tree using an application running on their system, which indicates that there have been changes and that a new version has been published. Then all of the directory trees on the clients are updated to the new version. 
     A problem occurs due to the use of the package format where there is a difference within a file. Using the above directory structure, changes to the file itself require the downloading of the entire file. Also, the checksums as described above cannot be used for each file above where a change in one file may cause the checksum for all other files in the package that come after the file to be different. 
     In an alternative embodiment, the difference between two binary files is computed. This computation may be done by a numerous method such as X-Delta (sourcefurge.net/projects/xdelta), BSDiff (Colin Percival, “Naïve Differences of Executable Cache,” Oxford University). Once the differences can be computed, a difference file is provided instead of downloading the new version. The client receives the difference file and combines it with the original, or earlier, version to create the new version. The difference file may be created by the NOC or, alternatively, by the content provider itself. Creating a new file from an earlier file and a difference file is well known in the art. 
     Target Locations 
     In one embodiment, the field in the object specification determines where on the recipient&#39;s device the file should be stored. Normally, content downloaded by the client in response to a NOC request is stored in a random directory. However, for certain application programs, the file is stored in a specific directory. For example, games or other similar application programs, such as help programs, often require specific pages to be added or replaced into specific directories. 
     To implement the target location feature, certain variables may be used as part of the path name. For example, a target location string such as “$WINDOWS:$PROGRAMS\abc”would cause a Windows client machine to store the object as “\\Program Files\\abc.” In this example, if the client machine does not run Windows, the file would be stored in the default (random) location. 
     If an object contains multiple target-location strings for different operating systems, such as “$WINDOWS:$PROGRAMS\abc” and “$LINUX:$PROGRAMS\abc,” the client automatically selects the suitable target location based on its operating system. 
     In one embodiment, to specify the directory, the NOC may ask the client to specify where the particular directory is installed on the client machine. Such a command may request where in the local memory the software for a particular application is stored. 
     Note when multiple versions of a particular program may be utilized, the client may have to indicate what version is available. This may be done through the use of variables wherein which version of, for example, Windows, is being used and specified to the NOC. 
     In one embodiment, security is in place to prevent replacing existing files on a machine unless there is permission. For example, in one embodiment, where files in certain directories cannot be replaced. 
     Presentation of Objects 
     As discussed above, the techniques described herein allow for presenting information in useful ways to a user. In one embodiment, pages are generated dynamically using a local approach. In the local approach, the web page is dynamically generated based on information at the client. In other words, the resulting page that is rendered is based on local information, not content provider (e.g., server) information. The dynamic generation of the content object allows different versions of the object to be displayed based on the information at the client. For example, the page may only be displayed with objects that are already cached. For another example, the pages may be displayed with a particular logo on an object to indicate the object is in the cache or may have cached objects displayed differently (e.g., more prominently) than non-cached objects. 
     In the local approach, the content provider supplies the web page. As the web page comes to the client, the browser&#39;s request information from an agent running on the client (i.e., the object agent) to determine if objects set forth therein are cached locally and sends information to the browser regarding the cached objects so that the browser can change the web page to reflect information from the profile and the cached object(s). In one embodiment, the web page contains a program, or script. In one embodiment, the program may comprise JavaScript or another scripting language. 
     Subscribing to Chapters 
     In one embodiment, content providers can make a user subscribe to a chapter by providing a “subscribe” link on any of their web pages. In one embodiment, when a user clicks on a link, the client goes to the site and the site provides an indication of how to add a chapter to his/her profile. When the user clicks on this link to add a chapter to the profile, instead of going to the remote web site, the user is taken to the middleware agent running on the same machine. This agent returns a page asking the user to confirm whether they want to subscribe to the chapter. The page may result in a pop-up dialog, or it could be a normal web dialog. When the user hits the “confirm” button, the chapter is added to the profile. 
     An Exemplary Protocol 
       FIG. 6  illustrates one embodiment of a protocol for exchanging information between master controller  501  and a client, a server, and a peer. Referring to  FIG. 6 , initially, when the client first boots up, the client registers ( 601 ). Registration by the client involves sending information to enable master controller  501  to coordinate the precaching activity. 
     In one embodiment, once registration has been completed, all but one of the remaining operations are controlled from master controller  501  (e.g., in response to a NOC request or message). Thus, master controller  501  sends a request to which the client replies, with the exception of one situation. 
     After registration, master controller  501  requests the profile from the client ( 602 ). In one embodiment, master controller  501  indicates the size of the profile it is willing to accept or is able to accommodate. Then the client sends the profile to master controller  501  ( 622 ). In one embodiment, the profile is a list of content objects (e.g., 50 to 100 URLs) in order of access frequency, with content objects that are accessed more often being at the top of the profile. If the profile is larger than the maximum specified by master controller  501 , the profile may be made smaller by the client by removing links that have been accessed less frequently (e.g., that are at the bottom of the list of links). 
     Similarly, master controller  501  communicates with the web servers (e.g., content providers). A server registers with master controller  501  ( 603 ). In response to the registration, master controller  501  requests state information from the server ( 604 ). This request may be generated by master controller  501  periodically while the server remains registered. In response to the request, the server sends state information ( 605 ). The state information may include a listing of all content objects that are linked through the sites. The list may be limited to only those content objects that are rich media objects or bandwidth intensive objects in terms of downloading. Every time new content is added or removed, the server sends an add message ( 606 ) or a remove message ( 607 ) to master controller  501  to update the list (e.g., in a database) master controller  501  maintains of the content objects linked through the site. 
     In one embodiment, master controller  501  initiates one or more maintenance tests on the client ( 621 ). These tests are well known in the art. For example, master controller  501  can request traceroutes from this client to some other Internet address or a bandwidth test from the client to a different Internet address. Master controller  501  uses these tests to determine network connectivity and resource availability. With this information, master controller  501  is able to obtain information about the network topology, a network map, etc., as listed above. Note that such information may be provided to master controller  501  directly without the need of testing to discover it. At this point, master controller  501  has information about network topology, information about server size state, and information about clients. 
     In one embodiment, master controller  501  may send a reset cache message ( 609 ) if a cache checksum doesn&#39;t match a previously defined or calculated value. 
     Master controller  501  keeps track of where the content is. Specifically, master controller  501  keeps track of a particular content piece (e.g., video clips) and the identity of the servers and/or clients on which it is located. Occasionally, master controller  501  determines that a client is to download some object from a location and at this time, master controller  501  sends an initiate download message ( 610 ) to the client that identifies an object and the object&#39;s location. In one embodiment, the initiate download message includes the name of the object (e.g., universal resource identifier (URI) and its natural location (e.g., a URL corresponding to its location on the server of its origin, a URL corresponding to some peer client, etc.)). 
     In response to the download message, the client initiates the download by sending a get data command to a peer ( 611 ). After the peer begins to send the data ( 623 ), the client sends a message to master controller  501  indicating that the download has started ( 612 ). The download may take a while. Once the download has been completed, then the client sends a message to master controller  501  indicating that the download has been completed ( 613 ). This allows master controller  501  to know which downloads are occurring at any time. 
     In case the peer is behind a firewall, then the client cannot connect to the peer directly and download the data from behind the firewall. In that case, master controller  501  sends a message ( 615 ) directly to the peer to indicate that the peer is to upload the new content to the client. Master controller  501  also sends a message to the client to expect an upload ( 614 ) from some peer. A particular session key or number may be used to correlate uploaded information received by the client from other peer clients with the correct download identified by master controller  501 . The peer sends the upload ( 616 ). Finally, the client sends a heartbeat message ( 617 ) to master controller  501  so that master controller  501  knows that the client is up in and running. 
     In one embodiment, the messages are small. Therefore, because almost all requests come from master controller  501 , master controller  501  is able to schedule all the downloads to ensure that no single client or network link is being overloaded. 
     Building User Profiles 
     The client creates a profile for an end user that is coupled to the client. The profile may comprise a list of resource locators (e.g., URLs), object type, object size, and a time stamp associated with the URLs to provide information as to when the end user accessed the resource. In one embodiment, the profile comprises URLs and access times, identifying web sites or portions of web sites, and when the user tends to access them. 
     Profiles may be configured by, or built, using input from a network administrator or manager, such as master controller  501  in the NOC. For example, the master controller  501  could add or remove URLs and access times. To make a change to the profile, the client would be accessible via the network, such as by, for example, an Internet service provider (ISP), application service provider (ASP), or content provider, and the profile could be configured through that access. An example of its use might be where the ISP provides a service by which a video movie is provided once a day to an end user. The individual could choose to watch the movie or not because the movie would have been already downloaded. Profiles may also be configured by a content server or a content provider. 
     Alternatively, the profile may be manually set by an individual, such as, for example, the user. The user may provide the specific URLs and access times manually to the profile. For example, if a user checks a set of web sites at a predetermined time during the day, the user can configure the network access gateway to access the web sites prior to that time each day to obtain updated or new content. Such additions to the profile augment the accuracy of the precaching. 
     A profile may be developed for a user using a combination of two or more of these profile-building methods. Further priorities can be assigned to URLs stored in the precache memory in case of conflicting access times. In one embodiment, user configured URLs have priority over learned URLs (developed from tracking user access patterns) and network administrator configured URLs (e.g., from master controller  501 ). 
     In one embodiment, only one precaching client is running on a system at any one time. An open application program interface (API) to the profile may be provided to allow third parties to add URLs to user profiles, to schedule downloads, and to use the services provided by the precaching architecture for their applications. 
     Locating New Content 
     In one embodiment, clients may check for new content by subscribing with master controller  501  in the NOC. Clients  503  can subscribe with master controller  501  to get automatic notification when new content becomes available. This is advantageous on large web sites with millions of clients because it reduces, or even minimizes, time and resources used in crawling. 
     Using the information stored in the user profiles, master controller  501  periodically checks for new content. To facilitate this, client  503  may have previously passed updates to its profile, such as shown as arrow  310  in  FIG. 3 . Master controller  510  maintains a list of web sites and their embedded media objects. This list is compiled by using updated information from content providers  502 , such as, for example, shown as arrows  210  and  230  in  FIG. 2 , or by crawling web sites from the NOC, such as shown as arrow  240  in  FIG. 2 . The crawling process is similar to the way in which some Internet search engines create indices of web pages. 
     In one embodiment, content providers  502  support the system by periodically crawling locally all available web pages on their servers to look for new object content. This local crawl can be implemented by software, hardware or a combination of both. 
     The content providers  502  provide a summary of changes to master controller  501 . Alternatively, such information may be provided directly to a client. The summary information may comprise the link, time, type and size of each object. The summary may include a list of URLs for those objects. The master controller compares the content in the list with the profile information (e.g., the list maintained by the network access gateway) to determine what content has changed and therefore what content, if any, is to be downloaded. In one embodiment, the result of the local crawl is made available in a special file, namely an update index. Master controller  501  analyzes the update index to find the new download candidates. In one embodiment, content providers  502  manually build an update index. 
     Master controller  501  collects and aggregates the summaries. In one embodiment, each content provider  502  sends the summary to master controller  501 . In such a case, all the clients need only contact one server to download summary information for groups of participating content servers in the network. In one embodiment, master controller  501  may unicast or multicast the information to one or more clients  503 . 
     In an embodiment in which clients maintain their own profile, such as described in U.S. application Ser. No. 09/566,068, entitled “Intelligent Content Precaching,” filed May 5, 2000, assigned to the corporate assignee of the present invention and incorporated herein by reference, clients  503  directly crawl a web site and search for new content objects. Clients  503  perform a crawl operation by periodically checking web servers indicated in the profile for new or updated content objects that it believes end users or other local devices will be accessing in the near future. In one embodiment, in such a case, a client begins with a URL stored in the profile and follows links into web pages down to a configurable level. 
     In one embodiment, the controller obtains the first page from the server and determines if any bandwidth intensive objects are present. In one embodiment, a bandwidth intensive object may be identified by its size. If bandwidth intensive, embedded objects exist, the controller determines if new versions are available and downloads them. When new content objects have been identified, the controller indicates to the client to download only the bandwidth intensive (e.g., large), new content objects (as they become available). The content objects obtained as a result of crawling are stored locally. In one embodiment, the precache memory storing such objects also stores their URLs, data type, size, the time when the data was acquired and the actual data itself. This process is transparent to the network and no change is needed to the content servers or the network to operate the precaching client. 
     In an alternative embodiment, each new and/or updated content object is downloaded independent of size (after determining if the content object is a new version). 
     Some or all of these crawling techniques may be used in the same networked environment. For example, client  503  may crawl one or more sites to determine if any of the content objects have changed, while receiving information from master controller  501  or web servers employing a mechanism to crawl their sites to identify updated or new content and while caches in the network or content servers provide updated and new content to the client  503 . 
     Downloading 
     Master controller  501  in the NOC maintains a database of available objects and their physical location. When a new object is available for downloading to client  503 , master controller  501  determines the most suitable location from which client  503  may download the object. In one embodiment, master controller  501  does this by analyzing the database and the client&#39;s Internet protocol (IP) address, and relating this to network topology, map, and connectivity information known to it. A scheduler in the NOC returns a download trigger to client  503 . The trigger provides information to enable client  503  to download the object. This trigger information, or pointer, may comprise a location and an object name (e.g., URL). 
     A requested object can be downloaded from a variety of sources, e.g. a peer, a carrier edge cache, or the original server. In  FIG. 5 , arrow  530  represents a download from a peer. Management controller  501  determines the most suitable host based on parameters. In one embodiment, these parameters include peer-to-peer hop count and bandwidth. 
     If no suitable peer is available (e.g., if the request is the first request for an object or if suitable peers are too far away), the object can also be downloaded from a server installed on the carrier edge if the content provider supports carrier edge caching. If there is no suitable peer and no cache can be found, the object is downloaded from the original content provider server  502 . Client  503  downloads the object in the background without excessively interfering with interactive traffic, regardless of the location from which it downloads. 
     Applications 
     The peer-to-peer precaching technique facilitates provision of premium services, such as explicit downloads, mapped content, aggregated access statistics, etc. The premium service of explicit downloads is done by triggering operations (potentially at regular intervals or at specific times) to pull the customer&#39;s content (e.g., all new clips on a web site immediately go to all sites with the web site&#39;s URL in their profiles). 
     Mapped content allows customers to offer dense content dedicated to precache-enabled users. In one embodiment, this is implemented by offering a separate high resolution file of a video clip which is not linked into any web page, but is available to the master controller when it checks a target web site for new content. When the user clicks on a video icon on a web page, the transparent precache technology delivers the high resolution version instead of the potentially low resolution version. 
     In aggregated access statistics, access statistics and user profile statistics are provided to content providers and distributors. For example, individual user access profiles on the customer premises are retained, with the statistics being reported. By only reporting the aggregated statistics, privacy concerns are avoided. 
     Besides enhancing traditional web sites with high-quality video, the precaching technique can be applied in other areas, such as advertising, and DVD on demand. Running decent quality video advertising over the Internet has not been possible so far. A broadband connection can barely deliver a single low-quality video stream, and consumers would certainly not want video ads to eat up their interactive bandwidth. Thus, advertisers are currently limited to using “banner ads,” which are mostly implemented as blinking images (animated GIFs). With precaching, advertisements can be downloaded while the link is not used otherwise. Thus, full motion ads can be downloaded in the background, and embedded in web pages, without exhausting the interactive bandwidth. The peer-to-peer video precaching technique helps advertisers to succeed in their hunt for eye balls. In addition, the precaching technique allows the advertisers and content providers to retain their ability to keep track of the number of “hits” of the embedded ads. 
     The precaching technique also makes online distribution of DVD video feasible. The hassle with late fees, midnight video store runs and rewinding charges would be avoided using an online renting model. MPEG2 video, the coding standard used on DVDs, requires an average bandwidth of 3.7 Mbits/sec. The average length of a DVD movie is two hours. An average movie needs approximately 3.5 Gbytes of disk space. Over a 500 kbits/sec Internet connection, three hours of DVD-quality movie can be downloaded in 24 hours. If the connection is twice as fast (e.g., 1 Mbit/sec), three full DVD movies can be delivered over the Internet in a day. 
     Thus, a technique of personalized content delivery using peer-to-peer precaching has been described. In particular, this technique saves content providers bandwidth on their server farms and carrier edge caches. It also improves the interactive experience of a large number of web sites. While the previous discussion focuses on clients running on end system PCs, the technique can be implemented to run in access gateways, home gateways, set-top boxes, etc. 
     An Exemplary Computer System 
       FIG. 7  is a block diagram of an exemplary computer system (e.g., PC, workstation, etc.) that may be used to provide one or more of the operations described herein. Referring to  FIG. 7 , computer system  700  may comprise an exemplary client  503  or server  502  computer system. Computer system  700  comprises a communication mechanism or bus  711  for communicating information, and a processor  712  coupled with bus  711  for processing information. Processor  712  includes a microprocessor, but is not limited to a microprocessor, such as, for example, Pentium™, PowerPC™, Alpha™, etc. 
     System  700  further comprises a random access memory (RAM), or other dynamic storage device  704  (referred to as main memory) coupled to bus  711  for storing information and instructions to be executed by processor  712 . Main memory  704  also may be used for storing temporary variables or other intermediate information during execution of instructions by processor  712 . 
     Computer system  700  also comprises a read only memory (ROM) and/or other static storage device  706  coupled to bus  711  for storing static information and instructions for processor  712 , and a data storage device  707 , such as a magnetic disk or optical disk and its corresponding disk drive. Data storage device  707  is coupled to bus  711  for storing information and instructions. 
     Computer system  700  may further be coupled to a display device  721 , such as a cathode ray tube (CRT) or liquid crystal display (LCD), coupled to bus  711  for displaying information to a computer user. An alphanumeric input device  722 , including alphanumeric and other keys, may also be coupled to bus  711  for communicating information and command selections to processor  712 . An additional user input device is cursor control  723 , such as a mouse, trackball, trackpad, stylus, or cursor direction keys, coupled to bus  711  for communicating direction information and command selections to processor  712 , and for controlling cursor movement on display  721 . 
     Another device that may be coupled to bus  711  is hard copy device  724 , which may be used for printing instructions, data, or other information on a medium such as paper, film, or similar types of media. Furthermore, a sound recording and playback device, such as a speaker and/or microphone may optionally be coupled to bus  711  for audio interfacing with computer system  700 . Another device that may be coupled to bus  711  is a wired/wireless communication capability  725  to communication to a phone or handheld palm device. 
     Note that any or all of the components of system  700  and associated hardware may be used in the present invention. However, it can be appreciated that other configurations of the computer system may include some or all of the devices. 
     Whereas many alterations and modifications of the present invention will no doubt become apparent to a person of ordinary skill in the art after having read the foregoing description, it is to be understood that any particular embodiment shown and described by way of illustration is in no way intended to be considered limiting. Therefore, references to details of various embodiments are not intended to limit the scope of the claims, which in themselves recite only those features regarded as essential to the invention.