WO1997008874A1 - Ameliorations relatives aux reseaux de communications - Google Patents

Ameliorations relatives aux reseaux de communications Download PDF

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Publication number
WO1997008874A1
WO1997008874A1 PCT/GB1996/002058 GB9602058W WO9708874A1 WO 1997008874 A1 WO1997008874 A1 WO 1997008874A1 GB 9602058 W GB9602058 W GB 9602058W WO 9708874 A1 WO9708874 A1 WO 9708874A1
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WO
WIPO (PCT)
Prior art keywords
frame
data
network
routing information
bridge
Prior art date
Application number
PCT/GB1996/002058
Other languages
English (en)
Inventor
Mark Kenneth Loney
Mark Alexander Leith Smallwood
Original Assignee
Madge Networks Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Madge Networks Limited filed Critical Madge Networks Limited
Priority to AU68275/96A priority Critical patent/AU6827596A/en
Publication of WO1997008874A1 publication Critical patent/WO1997008874A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
    • H04L12/46—Interconnection of networks
    • H04L12/4604—LAN interconnection over a backbone network, e.g. Internet, Frame Relay
    • H04L12/462—LAN interconnection over a bridge based backbone
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
    • H04L12/42—Loop networks
    • H04L2012/421—Interconnected ring systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
    • H04L12/44—Star or tree networks
    • H04L2012/445—Star or tree networks with switching in a hub, e.g. ETHERNET switch

Definitions

  • the invention relates to communication network and in particular a connecting device for such a network.
  • networks to which the invention apply include token passing rings as well as FDDI networks.
  • This frame is then sent around the first network until it reaches the bridge which recognises that the frame is destined for an end station on another network and so diverts the frame into its memory.
  • a controller within the bridge device reviews the frame once it is received in the memory to determine on which output port it should be directed (since typically a bridge device will be connected to more than two networks) , and in some cases will make changes in the control information, following which the frame is sent out onto the desired output port for onward transmission.
  • the destination end station may be on the output ring or the frame may have to traverse one or more further bridge devices.
  • the routing of a frame through a bridge device is generally carried out using one of two techniques.
  • an end station transmits a special Source Route Broadcast frame which is transmitted to all end stations on all networks and, as it passes through each bridge device, is modified to indicate the network on to which it is being transmitted.
  • the source route broadcast frame includes the desired destination end station identifier and once that end station receives the broadcast frame it indicates its presence and the frame is returned to the originating end station.
  • the originating end station can determine from the information now contained in the returned frame the identities of the various networks and bridges through which the frame has passed and this information is incorporated into the data frame which is to be sent so as to control the routing of the data frame.
  • each bridge device contains a look-up table which is continuously updated with information defining for each end station on all the networks the output port of the bridge concerned to which a frame directed to that end station should be coupled. This information is built up by the bridge by monitoring source addresses on incoming frames.
  • Conventional bridge devices require a significant amount of time to pass frames between networks. For example, delays of as much as 2000-3000 microseconds can be introduced, depending on the size of the frame. The delay, or latency, introduced by bridge devices can severely degrade network performance with today's applications, and make it virtually impossible to support emerging applications such as network video and multi media.
  • a connecting device for connecting a communication network to a bridge device for transferring data to another network in which each network carries data in frames including routing information associated with the data comprises an analysing unit for monitoring an arriving data frame, the analysing unit being adapted to monitor the routing information in the frame and to generate control data relating to the routing information; and output ports through which the control data and the frame respectively are supplied to a connected bridge device.
  • the connecting device further comprises a memory for storing addresses of end stations to which an incoming frame may be routed, the analysing unit being adapted to compare the routing information with the stored end station addresses and to generate control data to indicate a match, where appropriate.
  • control data can be used to indicate other routing information such as the address of another network or bridge device.
  • control data is generated for each byte of the frame and is typically passed in parallel with the corresponding byte through the output ports.
  • the control data will usually include a "null" byte since for many frame bytes, an active control data byte will not be required.
  • an interface unit positioned between the analysing unit and the communication network to extract a clock signal from the communication network and to form a digital data stream which is supplied to the analysing unit.
  • a further advantage of providing a separate connecting device is that an additional monitoring device could be provided for monitoring the output from one or a number of the output ports. This provides a convenient way of monitoring the flow of data along the network.
  • the device may further include an auxiliary analyser for monitoring the output from one or a number of the output ports and for generating an override control signal which is supplied to the bridge device if the frame routing information satisfies a predetermined condition. This is particularly useful where transparent bridging is carried out and where the connecting device may have indicated that the frame was not apparently destined for the connected bridge device since no address match was detected but in fact the frame is intended to pass through the bridge device under a transparent bridging protocol.
  • the transmitting means is preferably responsive to a control signal from the auxiliary analyser to modify a data frame which has been transmitted onto the network. This enables the frame to be modified to indicate that a match has occurred and, where appropriate, that a copy of the frame has been passed to the connected bridge device. In a token ring protocol, this would involve setting the ARI and FCI bits appropriately.
  • the connecting device will further comprise transmitting means for transmitting data frames onto the communication network, the transmitting means being connectable either to pass an incoming frame directly through onto the network or to pass a data frame from the bridge device to the network.
  • Figure 1 is a block diagram of the network
  • FIG. 2 is a block diagram of one of the connection devices used in Figure 1.
  • Figure 1 illustrates a token passing ring communication network formed by a set of four token passing rings 1-4 having respective addresses 123, 444, 456, and
  • Each ring 1-4 is connected to a number of end stations 5 such as PCs, file servers and the like, each having its own unique address.
  • the rings are connected together by bridges.
  • a bridge 6 connects the rings 1,2,3 and a bridge 7 connects the rings 3 and 4.
  • the connection to each bridge 6,7 is achieved via respective connection devices 8-12.
  • the connection devices 8-12 are identical.
  • each end station 5 could also be connected to the respective network via a similar connection device.
  • the bridges 6,7 can have a variety of conventional forms and a typical example is described in WO-A-95/04970. They could also be constructed as described in our British Patent Application No. 9518522.9.
  • FIG. 2 illustrates the construction of the connection device 8.
  • the input end of the ring 1 is connected to an analogue/digital converter interface 13 which extracts from the incoming electrical signal a clock signal and generates a clock signal output 14 and a digital, serial output 15 representing an incoming frame. These outputs are fed to a serial/parallel converter 16 which generates a digital, parallel output which is fed to an analysing unit 17.
  • the unit 17 has a number of parallel output ports 25 divided into two sets, one for control data bytes and the other for frame data bytes. The output ports are connected to the remainder of the bridge 6 as indicated schematically at 18.
  • Data to be transmitted onto the ring from the bridge device is fed to a transmitter unit 20 whose serial output is supplied to the interface 13 from where it is passed in analogue form onto the ring.
  • all incoming frames are passed to the analysis unit 17 whether or not they are destined for the attached bridge device. If the frame is not destined for the bridge device, it is fed out to the transmitter unit 20 along link 26. Otherwise, the analysis unit 17 monitors an incoming frame and generates a four bit control byte depending upon the information contained in the frame.
  • the format of a typical data frame according to the IEEE 802.5 protocol is set out below.
  • Routing Information for Source Routing
  • control data is generated according to the protocol set out in Table 1 below.
  • RX_DATA (SUCCESS 1) .
  • L l frame contains an error I Intermediate frame bit
  • Received EDI bit 1 0 0 xxxxxx TT TXCODE. Transmit completion code. Will not occur within a received frame. 1 0 1 xxxxxxxx RX_IDLE. Ignore idle cycles.
  • Each incoming byte of a frame is associated with a corresponding control data byte as will be explained below.
  • Table 2 sets out the frame data and corresponding control data which is generated by the analysis unit 17 in the device 8 when the frame is sent using a source route broadcast protocol in which the RI data defines the route of the frame.
  • the address of the station 5 on the ring 1 is ⁇ "123456789abc" and the address of the destination station 5 on the ring 4 "112233445566".
  • the ring 1 is identified as "123”, the bridge 6 as "a”, the ring 3 as
  • connection device 8 identifies from the sequence "123 a 456" that a match exists and thus generates a control data byte "0100" indicating success reason 2, i.e. a source routing match.
  • the next control data byte is expected to be success reason 3 and in this case is "0000" indicating that there are no other address matches.
  • the next control data byte "0010" (success reason 4) gives the index into the destination ring/bridge that generated the match. That is the location in the incoming frame of the destination ring/bridge identification data.
  • This control data is sent in parallel with the frame to the bridge device via the appropriate output ports 25.
  • control data enables the bridge device to act much more rapidly in routing the incoming frame by reference to the control data.
  • the connection device also includes a monitoring unit 21 which is attached to the output ports 25 from the analysis unit 17 and monitors the data transmitted from the output ports. Since the (frame) data output from one set of these ports is a copy of the data being transmitted around the ring, the monitoring unit 21 is able effectively to monitor the data passing around the ring for statistical and other purposes.
  • the analysis unit 17 is set up to handle source route broadcast switching. However, in some cases transparent bridging may be carried out and to deal with this a further processor 22 is provided. This is connected to the output ports 25 from the analysis unit 17 and also to the remainder of the bridge device 18 and to the transmission unit 20.
  • the analysis unit 17 will decide that there is no match with the destination address or routing information in the incoming frame and generate a corresponding (unsuccessful) control data output.
  • the unit 22 monitors the output from the analysis unit 17 and if it determines that the destination address of the incoming frame is matched with an address in its
  • the unit 22 will issue an override control to the remainder of the bridge device 18 to override the effect of the control data issued from the analysis unit
  • the unit 22 also controls the transmission unit 20 to modify a frame which has been received by the bridge device 6 by setting the appropriate bit or bits in the FCI or ARI field respectively. This is done “on the fly” as the frame is output by the transmission unit 20.
  • the transmission unit 20 can transmit data frames originating from the bridge device 18, in a conventional manner.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Small-Scale Networks (AREA)

Abstract

La présente invention concerne un système de connexion (8-12) d'un réseau de communications (1-4) à un dispositif en pont (6, 7), pour le transfert de données à un autre réseau, dans lequel chaque réseau transporte des données dans des trames incluant les informations d'acheminement correspondant aux données. Chaque système de connexion (8, 12) comprend une unité d'analyse (17) pour surveiller une trame de données qui arrive. Cette unité d'analyse est conçue pour surveiller les informations d'acheminement figurant dans la trame et pour produire des données de commande relatives aux informations d'acheminement. Le dispositif comprend également des ports de sortie (25) par lesquels les données de commande et la trame, respectivement, sont fournies à un dispositif à pont connecté.
PCT/GB1996/002058 1995-08-29 1996-08-22 Ameliorations relatives aux reseaux de communications WO1997008874A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU68275/96A AU6827596A (en) 1995-08-29 1996-08-22 Improvements relating to communication networks

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB9517618.6A GB9517618D0 (en) 1995-08-29 1995-08-29 Improvements relating to communication networks
GB9517618.6 1995-08-29

Publications (1)

Publication Number Publication Date
WO1997008874A1 true WO1997008874A1 (fr) 1997-03-06

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1996/002058 WO1997008874A1 (fr) 1995-08-29 1996-08-22 Ameliorations relatives aux reseaux de communications

Country Status (3)

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AU (1) AU6827596A (fr)
GB (1) GB9517618D0 (fr)
WO (1) WO1997008874A1 (fr)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4866421A (en) * 1987-06-18 1989-09-12 Texas Instruments Incorporated Communications circuit having an interface for external address decoding
EP0409539A2 (fr) * 1989-07-19 1991-01-23 NCR International, Inc. Méthode de routage pour les trames de réseaux de communication
US5245606A (en) * 1992-01-02 1993-09-14 National Semiconductor Corporation Computer network bridge circuit
EP0594198A2 (fr) * 1992-10-22 1994-04-27 Digital Equipment Corporation Commutateur à coordonnées pour la synthèse des topologies interconnectées à fonds de panier multiples

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4866421A (en) * 1987-06-18 1989-09-12 Texas Instruments Incorporated Communications circuit having an interface for external address decoding
EP0409539A2 (fr) * 1989-07-19 1991-01-23 NCR International, Inc. Méthode de routage pour les trames de réseaux de communication
US5245606A (en) * 1992-01-02 1993-09-14 National Semiconductor Corporation Computer network bridge circuit
EP0594198A2 (fr) * 1992-10-22 1994-04-27 Digital Equipment Corporation Commutateur à coordonnées pour la synthèse des topologies interconnectées à fonds de panier multiples

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
MARTINA ZITTERBART, AHMED N. TANTAWY, DIMITRIOS N. SERPANOS: "A High Performance Transparent Bridge", IEEE/ACM TRANSACTIONS ON NETWORKING, vol. 2, no. 4, August 1994 (1994-08-01), NEW YORK, US, pages 352 - 362, XP000477032 *

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Publication number Publication date
GB9517618D0 (en) 1995-11-01
AU6827596A (en) 1997-03-19

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