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%INC5%Usage of Preempt/Resume techniques for Multimedia transport over low-speed Frame Relay links Disclosure Number: IPCOM000013046D
Original Publication Date: 1999-Nov-01
Included in the Prior Art Database: 2003-Jun-12

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Didier Giroir


This paper relates to Frame Relay telecommunication networks and, more particularly, proposes the use of a mechanism to improve the quality of service provided by such Frame Relay networks when different flows of information, with different delay constraints are considered. This paper suggests to use between the Frame Relay switching nodes within the Frame Relay network that are interconnected via low speed links (i.e. Less than T3/E3 speeds), the improved preempt/resume protocol as described in "Method and Apparatus for Transmission of High Priority Traffic on High-Level Data Link Control-Like or Frame Relay Networks". This paper describing the improved preempt/resume protocol has been published in IBM's Topology Disclosure Bulletin v40 n1 p 1-4 in January 1997. For Frame Relay communication networks, there is a widely accepted requirement and a large potential market for the transport of some form of real time information, alongside with the regular data packets. Transporting variable length data packets was the original scope of the Frame Relay protocol, as opposed to Asynchronous Transfer Mode technology which has addressed from the very beginning the transport of multiple categories of data, including real time data. Transporting real time data traffic within Frame Relay networks allows for example, to use the existing infrastructure to carry not only computer related information but also the packets associated with (usually) low or medium quality voice circuits. Such real time packets would otherwise have to be transported over a totally different infrastructure than the Frame Relay network, with all the associated additional expenses. While this seems an achievable objective when modern high speed Frame Relay networks are concerned, the problem gets really complex in less sophisticated network infrastructure. Using this preempt/resume protocol between Frame Relay switching nodes allows Frame Relay networks using low speed lines (less than T3/E3 speeds) between some or all of the Frame Relay switching nodes composing the Frame Relay network, to support the transport of high priority traffic mixed with data traffic with less stringent delay constraints. The improved preempt/resume protocol allows such Frame Relay networks to transport delay sensitive information, such as voice packets. These voice packets may then coexist with variable length data packets, without the unacceptable impacts on delays and delay variations for the real-time traffic that are always associated with low-speed lines when variable length data packets of any size (up to the limit imposed by the Frame Relay protocols) are allowed to flow over such low-speed lines. The classical, well know problem occurs when a Frame Relay Switch starts transmitting some variable length data packet (whose length may be of several thousands of bytes) from a data packet virtual circuit and when during the current transmission, a real time packet (or many of these) is also ready for transmission on a different "real time" virtual circuit over the same transmission link. With regular link