COMMUNICATION SYSTEM COMPRISING A NETWORK AND CALL PROCESSOR

Abstract: A communication system comprises a network (5) connecting two or more end stations (1-4) and operating in accordance with a network protocol to make and break connections between the end stations. A call controller (8) is connected to the network (5), the call controller being responsive to call handling requests to generate instructions which cause the network to carry out the call handling requests while operating in accordance with the network protocol.

Description: COMMUNICATIONSYSTEMCOMPRISINGA NETWORKANDCALL PROCESSOR The invention relates to a communication system and is particularly concerned with communication systems for handling voice and video communications. Local area networks have been developed over the last few years to handle the communication of data between end stations such as PCs using certain network protocols such as token ring and ATM. However, these networks have typically been used for data communication only. Other forms of communication such as voice, video and the like have each been handled using separate communication systems with the result that a user needs to have available to him a range of devices suited to each type of medium. In accordance with one aspect of the present invention, a communication system comprises a network connecting two or more end stations and operating in accordance with a network protocol to make and break connections between the end stations; and a call controller connected to the network, the call controller being responsive to call handling requests to generate instructions which cause the network to carry out the call handling requests while operating in accordance with the network protocol. We have devised a method of adapting a communication system which includes a network such as an ATM network to enable it to provide a control for other media such as voice. In particular, the invention separates the primary low level connection features of a network, which consist essentially of the ability to make and break a connection between end stations, from higher level functions. The call controller is able to instruct the network or end stations to generate an appropriate combination of primitive make and break instructions so as to effect a call handling request. This enables the communication system to emulate a conventional voice communication system, for example, such as a PABX, which conventionally provides the user with a wide range of call handling facilities such as call transfer, call back and the like. Typically, the call controller will comprise a central unit but in some applications, more than one call controller could be provided, for example each call controller being associated with a local group of end stations. In a further example, the call controller could be distributed amongst all the end stations thus allowing the end stations to establish overlaid signalling channels to one another directly. In that case, the end stations will each contain software which implements higher level functions through a sequence of make-connection and break- connection commands to the network, under control of the overlaid signalling passing through the overlaid signalling channels which they establish between them. The call controller could be connected to each end station separately from the network but preferably the network also provides connection between the call controller and the end stations. This simplifies the physical structure of the system. Preferably, each active end station is permanently connected for message communication with the call controller although in some cases, in particular where the call controller is distributed amongst the end stations, the end stations are only connected to the call controller for exchange of call handling requests when a call handling request needs to be passed. Typically, the low level instructions to make or break connections from the call controller will be directed to one or more of the end stations but in some cases, the instructions could be directed to part of the network itself such as a network switch. The network can comprise any conventional communication network, primarily adapted for use as a local area network, for example an ATM network. In this latter case, the call handling requests from the call controller will typically include one or more ATM addresses of end stations together with a make/break connection instruction. Similarly, for other forms of network such as token ring, token ring addresses are passed. The end stations will typically comprise data/voice processing apparatus such as a PC but may also include transfer devices such as gateways to other communication systems. In particular, this allows the communication system to be connected to other voice communication systems such as the public switched telephone network. We also provide in accordance with a second aspect of the present invention, a call controller for connection to a network of a communication system according to the first aspect of the invention, the call controller comprising processing means responsive to call handling requests to generate and convey suitable instructions to the network to cause the network to carry out the call handling requests while operating in accordance with the network protocol. We have also appreciated that the inventive concept of separating the low level connection of devices through a network for information transfer, and the high level connection of devices for control purposes can be extended. Thus, in accordance with a third aspect of the present invention, a communication system comprises a network connecting two or more end stations and operating in accordance with a network protocol to make and break connections between the end stations, each end station including at least one information handling device; and a device controller for controlling the connection and configuration of the information handling devices both within and between the end stations. With this aspect of the invention, it is possible for the device controller to select particular information handling devices from the same or different end stations to process data in accordance with a particular data processing requirement. The information handling devices comprise any device which is capable of sending, receiving, or both sending and receiving, information traffic such as multimedia traffic. Examples include voice and video cards, network interface cards, a camera and a video screen. The third aspect of the present invention is particularly suited for use with the first and second aspects of the invention since this allows a call connection to be set up which takes account of changes in format of data generated at one end station and received at another end station as well as allowing the devices within an end station to be selected depending upon the type of data being transmitted. Thus, for example, if an end station is capable of handling both voice and video data, the device controller can select one or more devices within the end station for handling the particular type of data (voice or video) which is being transmitted. In this application, certain information handling devices may not be associated with call control functions. For example, a data compression device could be provided connected to the network, through which data is routed by the device controller, but which is located at an end station which does not itself initiate or receive calls. Typically, the device controller will include a store which contains information indicating for each end station the devices available so that the device controller can determine what devices are available at each end station involved in a connection and thus configure appropriate selections of devices. The information in the store may be updated dynamically as devices register and deregister with the device controller. Some examples of communication systems according to the invention will now be described with reference to the accompanying drawings, in which:- Figure 1 is a schematic diagram of an example of a communication system; and, Figure 2 is a schematic diagram illustrating the remote control of local devices. The communication system shown in Figure 1 comprises a number of end stations of which four 1-4 are shown. Each end station is connected to an ATM network 5 of conventional form and so the details are not shown in Figure 1. The end stations 1-3 have a similar construction. Each of the end stations 1-3 comprises a voice handling card IA, 2A, 3A connected to a telephone handset IB, 2B, 3B. A keyboard 1C, 2C, 3C is connected to an input interface ID, 2D, 3D. The voice card IA, 2A, 3A and input interface ID, 2D, 3D are connected to a network interface card IE, 2E, 3E each of which is connected to the network 5. The components IA, ID, IE are mounted within a PC having a processor IF. Similarly, the end stations 2,3 have processors 2F and 3F. The end station 4 comprises a wide area network (WAN) gateway which connects the network 5 with another network 6 such as a PSTN which provides communication to a large number of telephones such as a telephone 7. A central call controller 8 is provided which communicates with the network 5 and thus with the end stations 1-4. The call controller 8 includes a processor 9 and a store 10. When one end station wishes to communicate with another, the system operates as follows. At any instant, each active end station connected to the network 5, that is any end station which is able to receive or transmit calls, maintains an open channel of communication with the central controller 8 via the network 5. Physically, this channel of communication will be via a single connection from the end station to the network 5 although logically this channel must be distinguished from a channel which will be opened to carry voice or video data as will be described below. In this example, we will consider a call to be made between a user at end station 1 and a user at end station 2. Initially, the user at end station 1 enters an address, such as a telephone number, through the keyboard 1C of end station 2. This address is conveyed via the interface ID and interface IE through the network 5 along the open message channel to the central controller 8. The central controller 8 receives the message and determines that the user at end station 1 wishes to open a voice communication channel with the user at end station 2. By reference to information stored in the store 10, the processor 9 determines the ATM address of the end station 2 and transmits this address back to the end station 1 together with an instruction to cause the processor IF to construct an ATM message which will open a voice channel with the end station 2. This process will be conventional and utilise a conventional ATM protocol. Thereafter, the user at end station 1 can speak to the user at end station 2 via the network 5 with speech data being passed using the ATM protocol, the central controller playing no part in this communication. At the end of a call, the termination of the call will be notified back to the controller 8 which maintains a continuous monitoring of the performance of all the end stations attached to the network 5. The controller 8 will then issue an instruction to the end station to terminate the voice channel with the end station 2 using the ATM protocol. The advantage of the invention lies in the ability for permitting users of the end stations to request higher level functions other than simple make and break connection. For example, consider the situation in which the user of end station 1 wishes to transfer his call so that the user at end station 2 is connected to the user at end station 3. To achieve this, the user at end station 1 enters a "transfer call" instruction through the keyboard 1C which is transmitted through the message channel to the central controller 8. The central controller 8 then instructs the end station 1 to break the connection with the end station 2 and instructs the end station 2 to make a connection via the ATM protocol with the end station 3. The call then continues between the end stations 2 and 3. It is important to recognise that the network infrastructure does not need to understand "transfer" as a function, even in its external interfaces, but merely needs to provide make and break connection primitives. In the above description, the connection of a call was carried out by the end station 1 which had initiated the call connection instruction. However, it would also be possible for the central controller 8 to instruct the end station 2 to make the connection with the end station 1. In a further example, the controller 8 could instruct a switch within the network 5 to make connections with each of the end stations 1,2. This is sometimes known as "proxy signalling" within ATM. As mentioned above, although in the preferred example a single, central controller 8 is provided, more than one central controller could be used, particularly where there are groups of end stations in geographically remote locations. Furthermore, it would also be possible to omit a single unit for the central controller completely and allow the end stations to establish overlaid signalling channels to one another directly. The end stations will then contain the software which implements higher level functions through a sequence of make-connection and break- connection commands to the network infrastructure, under control of the overlaid signalling passing through the overlaid signalling channels which they establish between them. In this case, it is possible, optionally, only to establish the overlaid signalling channels when a message needs to be passed and in this way avoid requiring a permanent n x n way mesh of signalling channels between end stations. As far as the end station 4 is concerned, the controller 8 will treat this in a similar way to the other end stations but where a call is to be connected from one of the end stations 1-3 through the gateway 4 to the network 6, the central controller 8 will initially notify the gateway 4 to expect a call and the address of the final destination. Once the gateway 4 has determined that the final destination has been accessed, it will then notify the central controller 8 which in turn will notify the originating end station to set up a connection between itself and the gateway 4 using the ATM protocol. So far, we have described each end station as being treated as a single unit by the controller 8. We have realised, however, that it is possible for individual devices within the end stations to be controlled by the central controller 8. Within each end station, local interfaces (APIs) exist to allow manipulation of the device. Examples of such devices would include a sound- card; a video camera; and compression hardware. "Device control" consists of the ability to address these local device APIs. The basic primitives of device control are: 1. Make traffic-source. 2. Make traffic-sink. 3. Locally connect a given source to a given sink. Some devices accept only duplex links (e.g. telephones in most situations) , some can act only as a source (e.g. a camera) , some only as a sink (e.g. a video screen) . Different devices may have vastly more complex APIs for their manipulation (e.g. "focus" for a camera) . Some of these commands may change the traffic which flows between sources and sinks. However, creation and destruction of sources and sinks, together with their local connection, remain the core primitives of device control. Within the context of device control, a network- interface device is simply another device. When it creates a source it is collecting a traffic stream from the network, and conversely when it creates a sink it is delivering a traffic stream to the network. It's "make source" and "make sink" primitives may be parameterised by the remote network address to which it is to attach for the purposes of sending and receiving data respectively. A particular network end station may have several network-interface devices (indeed, they can be added and removed dynamically, as can other devices) , and hence can have several network addresses. In the context of local device control, the network-interface is not a privileged device but simply one among several. The control of devices is to be done remotely, by a centralised server resource. This server could be implemented in a distributed manner, but logically it is a central resource sitting at the centre of the network. Devices, including network-interface devices, make themselves known to the control server 8. This registration process conveys to the control server the type of the device, and also subsequently permits messages to travel between the call control server and the network stations. These messages can contain instructions for the control of the registered device(s) at the given network station. When devices register with a control server, they will be assigned to a particular user or group of users. This may be done on the basis of information provided by the device software, or by preconfigured information at the server, or both. Figure 2 illustrates in a schematic block diagram form the logical arrangement of devices and control. Thus, in this case, an end station is shown as comprising video software 20, sound software 21 and network traffic streaming software 22. These software components 20-22 are connected to a local traffic stream passing system 23. Each software unit is also connected to a message delivery system 24 which passes messages from the central controller (not shown) . These messages arrive in a similar manner to that shown in Figure 1 through the network and thus through a network interface card 25, a network protocol stack 26 and a message passing layer 27. In this way, the central controller 8 is able to select which of the software units 20-22 is to be used and in what manner (i.e. as a sink or source) . When local device control is used in conjunction with the call control system described with respect to Figure 1, a wide variety of different call connection functions can be set up by the central controller 8. Thus, when a call is requested, the central controller will instruct the connection of the call using its own rule system by manipulating the many local devices registered with it. The central controller may choose which devices it wishes to use during a call on any criteria it desires, including, but not only, making the best quality connection, making a connection of lowest cost, load balancing between different routes, taking note of which devices belong to users in the call and requests for a particular type of connection from the user. It should be noted that there need be no physical connection between call control applications (which asks for calls to be made and for things to be done to calls) and devices, including network-streaming software, which are manipulated by the central controller to form the initiation of the call. In Figure 2, a single network protocol stack 26 is shown. However, there could be more than one protocol stack providing links with different networks such as A to and Ethernet and these links could be through separate network interface cards or through a single card, for example in the case where an ATM network can be operated in the native mode and also while emulating TCPIP protocol.

Claims: CLAIMS 1. A communication system comprising a network connecting two or more end stations and operating in accordance with a network protocol to make and break connections between the end stations; and a call controller connected to the network, the call controller being responsive to call handling requests to generate instructions which cause the network to carry out the call handling requests while operating in accordance with the network protocol. 2. A system according to claim 1, wherein the call controller comprises a central unit. 3. A communication system according to claim 1 or claim 2, wherein the call controller is connected to each end station via the network. 4. A system according to any of the preceding claims, wherein the instructions from the call controller are directed to one or more of the end stations. 5. A system according to any of the preceding claims, wherein the network is an ATM network. 6. A system according to any of the preceding claims, wherein voice data is carried between connected end stations. 7. A call controller for connection to a network of a communication system according to any of the preceding claims, the call controller comprising processing means responsive to call handling requests to generate and convey suitable instructions to the network to cause the network to carry out the call handling requests while operating in accordance with the network protocol. 8. A communication system comprising a network connecting two or more end stations and operating in accordance with a network protocol to make and break connections between the end stations, each end station including at least one information handling device; and a device controller for controlling the connection and configuration of the information handling devices both within and between the end stations. 9. A system according to claim 8, wherein the at least one information handling device is capable of sending, receiving, or both sending and receiving multi media traffic. 10. A communication system according to any of claims 1 to 6 and any of claims 8 and 9.

Inventors: BERRINGTON NEIL, CROFT STEPHEN JOHN, GREATWOOD DUNCAN MACDOUGALL, BERRINGTON, NEIL, CROFT, STEPHEN, JOHN, GREATWOOD, DUNCAN, MACDOUGALL
Applicants: MADGE NETWORKS LTD, MADGE NETWORKS LIMITED
Application year: 1997
Main classification: H04Q11
IPC codes: H04L12, H04M3, H04Q3, H04Q11