WO2001078318A1

WO2001078318A1 - Method for establishing a logical connection in a telecommunication network

Info

Publication number: WO2001078318A1
Application number: PCT/US2001/011110
Authority: WO
Inventors: Gunnar A. Sjolund; Conway S. Cho
Original assignee: First Virtual Communications, Inc.
Priority date: 2000-04-05
Filing date: 2001-04-04
Publication date: 2001-10-18

Abstract

A method and apparatus are provided for interconnecting endpoints in a packet switched network wherein each link and endpoint in the network appears to be merely a receiver of an incoming call. In a specific embodiment, a Conferencing Management Controller (22) is provided which subsumes the functions of a multipoint control unit and Gatekeeper (24) without requiring the allocation of resources of a Media Processor to each link. In a more specific embodiment a conferencing management controller (22) comprises a Gatekeeper (24) with an associated Media (26) and Call Controller (27) for establishing calls to at least two endpoints as call receivers and directing the endpoints to communicate via direct path media for exchanging payload while maintaining control over the link.

Description

METHOD FOR ESTABLISHING A LOGICAL CONNECTION IN A TELECOMMUNICATION NETWORK

BACKGROUND OF THE INVENTION This invention relates to packet switched communication and in particular the invention related to the establishment of logical connections between two nodes at endpoints in a telecommunication network instigated by a third control point where the control point is resource constrained.

In 1996, the International Telecommunication Union adopted and published ITU-T Recommendation H.323 entitled "Visual Telephone Systems and Equipment for Local Area Networks Which Provide a Non-Guaranteed Quality of Service." This protocol specified the standards for video conferencing via packet-based or IP based networks. The H.323 Protocol also specifies centralized multipoint conferencing using an MCU which uses a Media Processor (MP) for mixing the media for distributing back to the endpoints.

Resources for establishing and supporting calls between terminal nodes or endpoints are frequently limited. In the past, in order to build a video-based call on a network between two clients on a network, calls had to be processed either directly between endpoints or through a Multipoint Control Unit (MCU) equipped with an MP. In each case, the Npplication Program Interface (NPI) of the call originating element must be exposed to the event trigger on the call originating element. If a third party device is to initiate the call, it must know of the NPI of each element to be able to work with the endpoint environment. This may be considered an intrusion in a proprietary system.

Referring to Figure 1, in a direct connection of the prior art, the initiating first endpoint (EPl) 5 using a closely coupled user interface queries a generic Gatekeeper (GK) 6 for permission to make a call to a particular telephone number, then the Gatekeeper 6 grants the first endpoint 4 permission to enter into a communication negotiation with the second endpoint (EP2) 7 by passing the network address of the second endpoint EP2 7 to the first endpoint EPl 5. Then the first endpoint EPl 5 negotiates and establishes a call to the second endpoint EP2 7 as the receiving party. The first endpoint 5 must initiate action to establish a call. Thereafter, the two endpoints can exchange payloads directly. Referring to Figure 2, in an MCU-mediated connection of the prior art, there is a gatekeeper which maintains an endpoint (EP) directory. The initiating first endpoint EPl 5 requests of an MCU 8 to establish a full point-to-point call using the resources of the MCU 8, and in particular using a media processor (MP) 9 on the MCU 8 allocated to the first endpoint EPl 5. The MP 9 is for mixing the payload for delivery to each of the endpoints via the high-bandwidth media 11 routed through the MCU 8. N call controller (CC) 13 in the MCU 8 functions to establish the call, and a multipoint controller (MC) 15 does the negotiations between endpoints. N device specific scheduler 17 within the MCU 8, which is closely associated with the functionality of the MCU 8 or knows intimately the functionality of the endpoints, must imtiate a call if the endpoint (e.g. EPl) does not initiate the call. The MCU 8 functionality is thus limited to a class of multiple point-to-point calls which requires the resources of the MP 9 for each connection.

There are two types of conferenced calling in the prior art: centralized and decentralized. Decentralized conferencing requires that endpoints have a media mixing capability. Centralized conferencing requires that a central switching point have a media mixing capability called a Media Processor (MP). What is needed is a mechanism applicable to video conferencing, which is noninvasive as to resource utilization and does not require the full resources to be concentrated at a central switching point or require endpoints to support decentralized conferencing. Thus, proprietary resources can be interconnected and conferenced with one another without having a need for full knowledge of internal operations of those resources.

SUMMARY OF THE INVENTION According to the invention, a method and apparatus are provided for interconnecting endpoints in a packet switched network wherein each link and endpoint in the network appears to be merely a receiver of an incoming call. In a specific embodiment, a conferencing management controller (CMC) is provided which subsumes the functions of an MCU and Gatekeeper without requiring the allocation of resources of an MP to each link. In a more specific embodiment a conferencing management controller comprise a Gatekeeper with an associated Media and Call Controller for establishing calls to at least two endpoints as call receivers and directing the endpoints to communicate via direct path media for exchanging payload while maintaining control over the link. The CMC does not need an MP in this type of call linkage. The CMC may also include an endpoint directory element and a user directory element, the user directory element for fielding call requests via a remote user interface or a local scheduler to initiate the calls such that the Gatekeeper and its associated Media and Call Controller function to initiate calls, while the endpoints serve merely to receive incoming calls. In a further embodiment, the CMC may use an MP element for mixing one set of the payload calls while directing that a subset of endpoints establish direct path media connections for exchanging payloads.

The invention has the advantage of making efficient use of resources by minimizing the requirement of payload mixing via the Media Processor function, while at the same time spoofing all nodes of the network so that it appears that only inbound calls are being processed at the nodes. Hence, there is no need to expose proprietary API elements of the nodes to other elements of the system.

The invention will be better understood by reference to the following detailed description in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a block diagram of a first prior art communication link. Figure 2 is a block diagram of a second prior art communication link. Figure 3 is a block diagram of a communication link for broadband connections according to a specific embodiment of the invention.

Figure 4 is a depiction of a protocol for establishing and controlling a communication link between endpoints via a CMC according to the invention.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS Referring to Figure 3, there is shown an apparatus 10 according to the invention for noninvasively interconnecting endpoints 12 and 14 in a packet switched network wherein each link and each endpoint 12 and 14 in the network appear to be merely a receiver of an incoming call. The apparatus 10 includes a conferencing management controller (CMC) 22 having at least a gatekeeper (GK) 24 and a multipoint controller (MC) 26 and call controller (CC) 27, as defined and specified by

Recommendation ITU-T H.323 (1996). Reference is made to this standard for further information about the scope and function of these elements. The MC 26 with CCs 27 as subunits is available from a variety of vendors, such as RAD Vision Inc. USA of Mahwah, New Jersey, Ezenia! Inc. (aka VideoServer) of Burlington, Massachusetts, Accord Telecommunications, Inc. of Atlanta, Georgia, and WhitePine Software, Inc. of Nashua, New Hampshire. Types of Gatekeepers 24 are also available from many of these sources. In addition a Gatekeeper 24 is available from FVC.COM, Inc., the original assignee of the present invention. The GK 24 performs conventional functions in connection with the invention of fielding both incoming and outgoing call requests and resolving network addresses.

A user directory 28 is a database application which maps entries of user numbers to entries in an endpoint directory 30. The endpoint directory 30 is a list of endpoint aliases which maps endpoint aliases to true endpoint network addresses for use by the GK 24. The MC 26 is for establishing calls to at least two endpoints 12 and 14. According to the invention, the MC 26 always initiates the calls to the" endpoints 12 and 14 so that each of the endpoints believes that it was the other endpoint that initiated the call. As call receivers, either endpoint 12 or 14 does not realize that the communication may have originated at the CMC 22 at the initiation of an external agent, such as a User Input 31 directing a request to the user directory 28. Each endpoint 12 or 14 and is made to believe that the call originated at the counterpart endpoint 14 or 12. Hence, the endpoints establish direct path media communications with one another via the path 40 as if each were receiving an incoming call. The endpoints thus exchange payload while the MC 26 remains in control over the link 40. Referring to Figure 4, there is shown a protocol diagram according to the invention which illustrates the inventive method. The MC 26, in response to an external prompt, initiates a setup command to each of the endpoints 12 and 14 (Step 1). In a specific embodiment, the MC 26 sends a setup command according to ΪTU-T recommendation Q.931 ("User-Network Interface Level 3 Specification for Basic Call Control" 1993). Thereafter each endpoint calls back to the GK 24 for permission to answer the call (Step 2). This is typically an ARQ (Admission ReQuest) according to RAS protocol ITU-T H.225 (1996). The GK 24 then issues an ACF (Admission ConFirm) according to the same RAS protocol to each of the endpoints 12 and 14 (Step 3). The endpoints confirm the setup by issuing a connect signal to the MC 26 according to the Q.931 protocol convention (Step 4). There is now a logical connection established between the two endpoints. Then two connections are established between the endpoints 12 and 14 and the MC 26, typically according to ITU-T Recommendation H.245 ("Control Protocol for Multimedia Communication" 1997) Step 5). This is the precursor to actual connection of a video stream whereby an endpoint reports its capabilities to each other. The endpoints do not realize that the transport is via the MC 26. Finally, based on the report of exchanged capabilities, direct media streams are opened between the endpoints 12 and 14 (Step 6). Typically four media streams are opened, two each for audio and video, to establish full duplex functionality. The invention does not require the use of a media processor (MP) as part of the transport of media streams. However, the invention can be used with MCUs which are equipped with MPs to facilitate multipoint simultaneous multiparty calls. In such an instance, a CMC controls MCU to establish calls, so that the MCUs each act as call- receiving endpoints. The MCUs then use their MP capabilities to carry and mix media traffic. Nevertheless the MCUs need not disclose their API interface to other nodes in the network.

The invention has been explained with reference to specific embodiments. Other embodiments will be evident to those of ordinary skill in the art. It is therefore not intended that this invention be limited except as indicated by the appended claims.

Claims

WHAT IS CLAIMED IS:

1. An apparatus for interconnecting endpoints in a packet switched network wherein each link and each endpoint in the network appears to be merely a receiver of an incoming call, said apparatus comprising: a conferencing management controller (CMC) having at least a gatekeeper (GK); and a multipoint and call controller (MC), the GK for fielding incoming call requests and resolving network addresses, and the MC for establishing calls to at least two endpoints as call receivers and directing the endpoints to communicate via direct path media for exchanging payload while maintaining control over the link.

2. The apparatus according to claim 1 further including a user directory element for fielding incoming call requests to the CMC and initiating call requests via the GK to the MC as a call receiver.

3. The apparatus according to claim 2 further including a scheduling element for initiating prescheduled incoming call requests via the directory element.

4. A method for building calls between endpoints in a packet switched communication network using a conferencing management controller (CMC), said method comprising: fielding incoming call requests and resolving network addresses in a gatekeeper (GK), establishing calls to at least two endpoints as call receivers using a multipoint controller (MC); and directing, via the MC, that the endpoints communicate via direct path media for exchanging payload while the MC maintains control over the link between the endpoints.

5. The method according to claim 4 further including the steps of using the CMC with a multipoint control unit (MCU) having a media processor (MP) to mix one set of the payload calls while directing that a subset of endpoints establish direct path media connections for exchanging payloads.