Multiplex communications – Data flow congestion prevention or control – Control of data admission to the network
Reexamination Certificate
1998-12-16
2003-03-04
Ngo, Ricky (Department: 2661)
Multiplex communications
Data flow congestion prevention or control
Control of data admission to the network
C370S232000, C370S235000, C709S223000
Reexamination Certificate
active
06529475
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates generally to a communications system and in particular to a method and system for improving flow of data traffic within a communications network. Still more particularly, the present invention relates to a method and system for improving flow of data traffic within a multimedia communications network by reducing congestion.
2. Description of the Related Art
The H.323 standard is an umbrella recommendation from the International Telecommunication Union (ITU) that sets standards for multimedia communications over Local Area Networks (LANs) that do not provide a guaranteed Quality of Service (QoS). These networks dominate today's corporate desktops and include packet-switched Transmission Control Protocol/Internet Protocol (TCP/IP) and Internet Packet Exchange (IPX) over Ethernet, Fast Ethernet and Token Ring network technologies. Therefore, the H.323 standard is an important building block for a broad new range of collaborative, LAN-based applications for multimedia communications.
The H.323 standard is the newest member of a family of ITU umbrella recommendations which cover video telephone multimedia communications over a variety of pipelines. The H.323 standard is in many senses a derivative of H.320, 1990 umbrella recommendation for video telephone over switched digital telephone networks. The H.323 standard borrows heavily from H.320's structure, modularity, and audio/video compression/ decompression (codec) recommendations.
The H.323 standard provides a foundation for audio, video, and data communications across IP based networks, including the Internet. By complying to the H.323 standard, multimedia products and applications from multiple vendors can interoperate, allowing users to communicate without concern for compatibility. The H.323 standard will be the keystone for LAN based products for consumer, business, entertainment, and professional applications.
Communications under the H.323 standard can be considered a mix of audio, video, and control signals. Audio capabilities, Q.931 call setup, RAS control, and H.245 signaling are required. All other capabilities including video and data conferencing are optional. When multiple algorithms are possible, the algorithm utilized by the encoder are derived from information passed by the decoder during the H.245 capability exchange. H.323 terminals are also capable of asymmetric operation (different encode and decode algorithm) and can send/receive more than one video and audio channel.
The H.323 standard addresses call control, multimedia management, and bandwidth management for point-to-point and multipoint conferences. It is designed to run on common network architectures. As network technology evolves, and as bandwidth management techniques improve, H.323-based solutions will be able to take advantage of the enhanced capabilities. The H.323 standard is not tied to any hardware or operating system and H.323-compliant platforms will be available in all sizes and shapes, including video-enabled personal computers, dedicated platforms, and turnkey boxes.
Often, users want to conference without worrying about compatibility at the receiving point. The H.323 standard establishes standards for compression and decompression of audio and video data streams, ensuring that equipment from different vendors will have some area of common support. Besides ensuring the receiver can decompress the information, the H.323 standard establishes methods for receiving clients to communicate capabilities to the sender. The standard also establishes common call setup and control protocols.
The H.323 standard utilizes both reliable and unreliable communications. Control signals and data require reliable transport because the signal must be received in the order in which they were sent and cannot be listed. Audio and video streams lose their value with time. If a packet is delayed, it may not have relevance to the end user. Audio and video signals utilize the more efficient but less reliable transport.
Because the H.323 standard is Real-Time Transport Protocol (RTP) based, it can operate on the Internet's Multicast Backbone (Mbone), a virtual network on top of the Internet that provides a multicast facility, and supports video, voice and data conferencing. The H.323 [H.323v2] standard has been proposed to perform call control (i.e. make connections) of real-time service on IP networks. The H.323 standard allows end-points or terminals wanting to make connections to negotiate bandwidth and coding requirements before the connection is established. In this standard there are three key players:
End-point: These are terminals which need to make connections. They request the connection through a gatekeeper (if one is on the network) and they also negotiate the connection parameters.
Gatekeeper: These entities perform bandwidth control (on LANs) and routing of connection packets towards the destination terminal.
Gateway: This entity can be thought of as a collection of end-points, but these entities also translate from other bearer protocols (such as time-division multiplexing (TDM)) to the IP protocol.
FIG. 1
clearly illustrates the interconnectivity of these components.
FIG. 1
depicts a network with several gatekeepers
100
, routers
101
, endpoints
102
, gateways
108
, and terminals
104
. Gatekeepers
100
, routers
101
, gateways
108
, endpoints
102
, and terminals
104
are interconnected via network links
106
. Note that gatekeepers
100
are linked together to form the framework of the network while gateways
108
, endpoints
102
and terminals
104
serve as the branches to this framework.
The Gatekeeper is a H.323 entity that provides address translation, control access, and sometimes bandwidth management to the LAN for H.323 terminals, Gateways, and Multipoint Control Units (MCUs). Gatekeepers perform two important call control functions which help preserve the integrity of the corporate data network. The first is address translation from LAN aliases for terminals and gateways to IPX addresses, as defined in the Registration/Admission/Status (RAS) specification. The second function is bandwidth management, which is also designated within RAS. For instance, if a network manager has specified a threshold for the number of simultaneous conferences on the LAN, the Gatekeeper can refuse to make any more connections once threshold is reached. The effect is to limit the total conferencing bandwidth to some fraction of the total available, the remaining capacity is left for email, file transfers, and other LAN protocols. The collection of all Terminals, Gateways and Multipoint Control Units managed by a single gatekeeper is known as a H.323 Zone.
Improvements in communications arise from changing user's needs and demands. Previously, public network needs were driven by telephoning and voice data. Data traffic has grown slowly until recently. With the lower cost in telecommunications and the higher increase in processing power of computers, the number of users accessing communications networks has increased. The needs of these users include, for example, video telephone, low cost video conferencing, imaging, high definition television (HDTV), and other applications requiring multimedia data transfers. Multimedia combines different forms of media in the communication of information between a user and a data processing system, such as a personal computer. A multimedia application is an application that utilizes different forms of communications within a single application. Multimedia applications may, for example, communicate data to a user on a computer via audio, text, and video simultaneously. Such multimedia applications are usually bit intensive, real time, and very demanding on communications networks.
The H.323 standard sets multimedia standards for the existing infrastructure (i.e. IP-based networks). Design to compensate for the effect of highly variable LAN latency, the H.323 standard allows customers to utilize multimedia applicati
Wan Guang
Weston-Dawkes Jonathan
Bracewell & Patterson L.L.P.
Gigliotti Thomas A.
Ngo Ricky
Nortel Networks Limited
Phan Tri H.
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