Multiplex communications – Pathfinding or routing – Through a circuit switch
Patent
1996-10-24
1999-12-07
Nguyen, Chau
Multiplex communications
Pathfinding or routing
Through a circuit switch
370380, 370395, H04L 1256
Patent
active
059995289
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates in general to digital communication systems, and more particularly to a novel switching system using asynchronous transfer mode (ATM) transmission and switching of information.
BACKGROUND OF THE INVENTION
The emergence of high-speed asynchronous transfer mode (ATM) communications is a recent result of the diverse demands now being made on enterprise backbone networks. Early enterprise networks were dominated by voice traffic with only a relatively small amount of circuit bandwidth devoted to data and other applications. More recently, a range of new applications has evolved resulting in significant changes to existing backbone networks. High-bandwidth video telephony and video conferencing, for example, are rapidly becoming essential requirements in digital communication systems. Similarly, the bandwidth requirements for LAN (Local Area Network) interconnection across multiple sites is also increasing as established prior art LAN systems such as Ethernet.TM. and Token Ring are upgraded to meet the demands of faster communication and more sophisticated processing.
For example, Fibre Distributed Data Interface (FDDI) LANs operating at 100 Mbps are presently being deployed while even higher bit rates LAN types are emerging as a result of text-based personal computers being replaced by multi-media work stations and associated servers. Typically, multi-media work stations and their associated servers support document architectures that comprise not only text but also high resolution still images and moving images with sound. Thus, instead of inter-site LAN traffic being dominated by file transfers of textual information as in the prior art, LAN file transfers in newer systems are migrating towards higher volume, high bit-rate mixed-media traffic.
The combined effect of such developments has necessitated the development of a more flexible method for the allocation of transmission bandwidth in order to efficiently utilize inter-site leased circuits associated with enterprise networks.
The developments discussed above are not limited to private networks, but are occurring in public carriers as well.
In order to meet these new demands in private and public digital communication systems, an international standard operating mode has been developed for use with broadband integrated services digital networks (BISDN) based on the asynchronous transfer mode (ATM) of transmission and switching. The aim of the ATM protocol is to provide a more flexible facility for the transmission and switching of mixed-media traffic comprising data, voice, still and moving images and video. Traditionally, constant bit rate traffic such as voice has been transmitted and switched using pre-assigned time slots, whereas data is normally transmitted in the form of variable length frames which are multiplexed together on a statistical basis. According to the ATM protocol, transmission and switching is performed on fixed-sized units referred to as "cells". Cells from different sources (eg. voice, data, video, etc.), are multiplexed together on a statistical basis for transmission purposes.
Each standard ATM cell is 53 bytes in length, comprising a 48-byte information field (also referred to as the "payload"), and a five-byte header containing routing and other fields.
Like packet and frame switching, ATM operates on a virtual call/connection basis. This means that prior to any user information cells being sent, a virtual connection is first placed through the network. During this phase, a virtual connection identifier (VCI) is assigned to the call at each interexchange link along the route. The assigned identifier, however, has only local significance to a link and changes from one link to the next as the cells relating to a connection pass therethrough. This means, therefore, that the routing information carried in each cell header can be relatively small.
In particular, each incoming link/port has associated therewith a routing table that contains the corresponding output link/port and a new V
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Bews Steve
Bisson Germain
Chow Henry
Gassewitz Michael
Ghadbane Jim
Newbridge Networks Corporation
Nguyen Chau
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