Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Patent
1997-02-04
1999-06-29
Hsu, Alpus H.
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
370466, 370471, 370474, H04L 1256
Patent
active
059178230
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a PVC backbone for packet switching networks capable of implementing CCITT X protocols, such as the X.25 protocol.
BACKGROUND OF THE INVENTION
The primary protocol to be implemented by the X.25 service is the X.25 CCITT standard, 1988 version. Other related protocols are X.75, X.32, and the "triple X" PAD (Packet Assembler-Dissembler) (X.3, X.28, X.29).
Until now, packet switches have been built on trunking and routing systems that use simple circuit switching or point-to-point data communications technologies. This provided no flexibility and control of the individual virtual circuits when parts of the backbone network became congested.
X.25 is an interface specification for statistically multiplexing several independent data streams onto common facilities. It uses a link layer based on HDLC frames, using LAPB between the DTE and the DCE.
An object of this invention is to provide an improved network supporting X-series packet and call protocol.
BRIEF SUMMARY OF THE INVENTION
Accordingly the present invention provides a packet switching network supporting X-series protocol access wherein PVC trunks are employed as the backbone trunks for the network.
The invention also provides a node for use in a data transmission system comprising a hardware platform having sufficient memory, processing power and fanout to support X-series protocol access; processing means providing support for HDLC and LAPB at the link level, and standard X-series packet and call-control protocol; a packet transport system for transmitting packets between data communications equipment (DCE's) with no errors, no loss and in-sequence; and a routing system to establish a virtual connection between DCEs within specified time limits, and maintain connectivity in the event of failures, errors and congestion.
Preferably, the node includes a management system that provides the configuration data for the above system, and integrated management services, a system for reliably gathering accounting data from the nodes, and a system for validating Network User Identifiers.
The X-series protocol may be X.25 operating at speeds of 9.6 K to T1/E1.
Each node that supporting X.25 has one or more X.25 Packet Engines. This Packet Engine supports X.25 interfaces to users on either its own access ports, or through subrate interfaces. The X.25 Packet Engines connect to other X.25 packet engines through frame relay PVCs. These PVCs terminate on software processes within the Packet Engines. They act as trunks over which the X.25 data packets are multiplexed by the X.25 transport and routing software on the Packet Engine.
This invention employs the frame relay protocol described in: ANSI T1.602, ANSI T1.606, ANSI T1S1/90-175, ANSI T1.617 - DSS 1, ANSI T1.618 - DSS1, CCITT Recommendation I.122, CCITT Recommendation Q.922, CCITT Recommendation Q.933.
The flow control procedures are based on CCITT Recommendation Q.922 and Frame Relay Forum Technical Committee Document Number FRFTC 92.15 "Frame Relay X.25 Interworking Implementation Agreement."
The X.25 protocol is described in CCITT Recommendation X.25.
The invention still further provides a method of transferring data comprising receiving X.25 LAPB frames, characterized in that it comprises the steps of establishing a permanent virtual connection between data communications equipment (DCE's), encapsulating the X.25 LAPB frames into frame relay frames and attaching a DLCI identifier, transmitting the encapsulated frames over bewteen the DCE's over the PVC, and stripping off the frame relay header from the received encapsulated frames to restore the LAPB frames.
This invention overcomes the above difficulties experienced in conventional systems by using PVCs, for example frame relay PVC's, as the backbone trunks for a packet switching network. This allows the use of frame relay explicit congestion notification to individually flow control virtual circuits. By integrating the frame relay PVCs into a routing system that monitors the states of the PVCs and uses an
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International Conference on Networks, Sep. 5, 1991, Singapore pp. 393-400 A.K. Roy, "Frame Relay and its Transport Dilemma" see the whole document.
Communications International, vol. 19, No. 2, Feb. 1992, GB pp. 46-48 N Rickard "Frame Relay the Best of Both Worlds?".
Allan Keith
Benning Rex
Hurd Jim
Hsu Alpus H.
Newbridge Networks Corporation
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