Bridge apparatus and a communication system between networks using the bridge apparatus

• US 5,220,562 A
• Filed: 05/08/1990
• Issued: 06/15/1993
• Est. Priority Date: 05/12/1989
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Nakamura, Kazunori, Kimura, Koichi, Hiyama, Kunio, Onishi, Katsuyoshi, Takada, Osamu, Takiyasu, Yoshihiro, Yamaga, Mitsuhiro
• Primary Examiner(s): Kuntz, Curtis
• Assistant Examiner(s): GHEBRETINSAE, TEMESGHEN
• Application Number:
  US07/520,712
• Time in Patent Office: 1,134 Days
• Field of Search: 370/85.13, 370/85.14, 370/85.15, 370/94.1, 370/60, 340/825.05, 340/825.5, 340/825.52
• US Class Current: 370/404
• CPC Class Codes: H04L 12/4616 LAN interconnection over a LAN backbone
• CPC Class Codes: H04L 45/742 Route cache; Operation thereof

Abstract

Frontend LANs connecting plural stations are connected to plural nodes of a backbone LAN respectively. The backbone LAN is constituted by plural physical or logical links, and each node corresponds to each frontend LAN. A first data block is segmented into one or plural second data block units of fixed length and transferred to destination nodes, a bridge is provided in order to assemble the second data blocks into the first data block. The bridge can transmit the second data blocks to arbitrary links, and the receiving is performed through one link. The bridge a decoder also has a decoder for decoding whether the learning should be performed or not, based on the learning indication information existing in the second data block including the routing information.

Claims

1. A communication system for inter-connecting a plurality of frontend networks with a loop-type backbone network, the communication system comprising:

the backbone network including a plurality of logical or physical highways;

at least one node means connected to the backbone network, said node means including a bridge means connected to a corresponding one of the frontend networks, said bridge means including

a segmenting means for segmenting a first data block of variable length received from the frontend network, into at least one of second data blocks of preselected, fixed length to be sent along the backbone network,

a searching means for searching a routing information table with a destination station address contained in said first data block,

a registering means for registering routing information including a source station address of said first data block in said routing information table, and

an assembling means for reassembling said first data block from at least one of said second data blocks received from the backbone network; and

a switching means for selectively connecting said bridge means to at least one of said backbone network highways to transmit said second data blocks along the backbone network.

2. The communication system according to claim 1, wherein said switching means connects said bridge means to all of said backbone network highways in order to broadcast forward said second data blocks in accordance with results of said searching means searching the routing information table.

3. The communication system according to claim 1, wherein each of said second data blocks has a learning indicator field and an error check field.

4. The communication system according to claim 1, wherein said node means includes a plurality of said bridge means.

5. The communication system according to claim 4,

wherein said switching means connects each of said bridge means to a predetermined one of said highways in order to receive said second data block from the backbone network.

6. The communication system according to claim 1, wherein said bridge means directly transmits at least one of said first data blocks reassembled by said assembling means to the frontend network connected to said bridge means when a transmission becomes ready.

7. The communication system according to claim 1, wherein

said assembling means includes a receive controller and a re-assemble buffer means, said re-assemble buffer means having a re-assemble management table and a set of fixed length buffers with a chain pointer, and

said receive controller includes means for storing said second data blocks consecutively received from said bridge means, and means for executing assembling said second data blocks transmitted from the bridge means to said first data block by using said chain pointer of said fixed length buffers and said re-assemble management table.

8. The communication system according to claim 1, wherein each of said second block has a backbone MAC header including at least a cell position field and a sequence number field, and said assembling means includes a receive controller for executing an error check of said cell position field and sequence number field.

9. The communication system according to claim 1, wherein said assembling means includes a receive controller having a group address register means for storing group address and a receive decision means for deciding to selectively receive one of said broadcasted second data blocks from said backbone network in accordance with said group address and destination address included in one of said broadcasted second data blocks so as to limit a number of said bridge means which can receive one of said broadcasted second data blocks.

10. A communication system for transferring data between a plurality of frontend networks with a loop-type backbone network, each of the frontend networks being connected with at least one station, the communication system comprising:

the backbone network including a plurality of physical or logical highways;

a plurality of nodes connected to the backbone network; and

,

each of the plurality of nodes including bridge means corresponding to frontend networks and a switching means for selectively connecting said bridge means to said highways, said bridge means including;

a first converting means for converting a first data block of variable length received from a corresponding frontend network into at least one second data block of fixed length, said first data block having a destination station address and a source station address, each second data block having error check information and learning indicator information to be transferred to the backbone network,

a second converting means for converting at least one of said second data blocks received from the backbone network into said first data block, and

a searching and registering means for searching a routing information table with said destination station address to determine at least one of said highways to be connected by said switching means on which to transmit said second data block and for registering routing information including said source station address in said routing information table.

11. The communication system according to claim 10, wherein said second data block is transferred from the backbone network with said error check information and said learning indicator information thereof, and

said searching and registering means executes a learning routine in response to said learning indicator information and an output of an error checking means.

12. The communication system according to claim 10, wherein each of said second data blocks has an AFC field including at least a learning indicator field, said learning indicator field being used as said learning indicator information.

13. The communication system according to claim 10, wherein each of said second data blocks has a backbone MAC header including at least a cell position field, said cell position field being used as said learning indicator information.

20. The node according to claim 13, wherein a plurality of said bridge means are connected to said loop access control means, and said routing information further includes a corresponding bridge address.

14. A method for transferring data between a plurality of frontend networks, each of the frontend networks connecting at least one station through bridge circuits to a backbone network, the backbone network including a plurality of physical or logical loop highways, the method comprising the steps of:

receiving a first data block of variable length having a destination and source station address from one of the frontend networks;

segmenting the first data block into at least one of fixed length second data blocks each including a control field having a learning indicator field, a content field, and an error check code field;

determining on which highway to transmit each second data block by searching a routing information table with said destination station address;

transmitting each second data block on the determined highway; and

registering routing information including said source station address of the corresponding segmented first data block in said routing information table.

15. The data transferring method according to claim 14, further comprising steps of:

checking said error check code field of said second data block transmitted from the backbone network.

16. The data transferring method according to claim 15, further comprising steps of:

learning said routing information derived from said second data block in accordance with said learning indicator field thereof and a result of said checking step.

17. In a communication system in which a plurality of frontend LANs which connect a plurality of stations are connected through a plurality of physical or logical loop highways, a node comprising:

a loop access control means for selecting the logical highways on which to transmit a plurality of fixed length backbone LAN cells to another node; and

a bridge means connected between said loop access control means and corresponding frontend LANs, said bridge means including a converting means for converting each variable length frontend LAN frame received from one of the frontend LANs into at least one of said backbone LAN cells, each of said backbone LAN cells having a learning indicator field and an error code check field.

18. The node according to claim 17, wherein said learning indicator field has information denoting whether said cell is a first, single one of said backbone LAN cells.

19. The node according to claim 18, further comprising:

a storing/searching means for storing routing information including a set of a station address and a node address, said storing/searching means storing said routing information in response to said learning indicator field when said node receives said backbone LAN cells from the physical or logical loop highways.

21. A communication system for communicating among a plurality of stations on a plurality of frontend LANs via a loop-type backbone LAN, the communication system comprising:

the backbone LAN including a plurality of physical or logical highways;

a bridge means connected to each of the frontend LANs, said bridge means including;

a segmenting means for segmenting a variable length first block from the frontend LAN to at least one of second data blocks, each of said second data blocks having a fixed length, and

a searching means for searching a routing information table with a destination table; and

a switching means for selectively connecting said bridge means to at least one of said logical highways to transfer said second data block to another one of the bridge means.

22. The communication system according to claim 21, wherein said bridge means further includes a re-assembling means for re-assembling said second data blocks received from the backbone LAN into said first data block.

23. A communication system for communicating among a plurality of stations on a plurality of frontend LANs via a backbone LAN, the communication system comprising:

a backbone LAN including a plurality of physical or logical highways;

a bridge means connected to each of the frontend LANs, said bridge means including;

a segmented means for segmenting a variable length first data block from the frontend LAN to at least one of second data blocks, each of said second data blocks having a fixed length, and

a searching means for searching a routing information table with a destination station address contained in said first data block; and

switching means for connecting said bridge means to all of said physical or logical highways to transfer said second data blocks by broadcast in accordance with a searching result of said searching means.

24. In a communication system between a plurality of stations connected to a plurality of frontend networks, each of the frontend networks being connected to one of a plurality nodes of a backbone network that includes a plurality of logical or physical loop highways, the one node having a routing information table, a method of learning routing information in the node comprising the steps of:

segmenting a frontend network frame received from the frontend network into at least one backbone network cell to be transmitted to the backbone network;

searching the routing information table to retrieve a search result corresponding to a destination station address contained in said frontend network frame; and

selecting one or all of the highways in response to the result of said searching step on which to transmit said backbone network cell to the backbone network.

25. In a communication system between a plurality of stations connected to a plurality of frontend networks, each of the frontend networks being connected to one of a plurality of nodes of a backbone network that includes a plurality of logical or physical loop highways, in which each node has a table for storing routing information, a means to convert first data block received from the frontend network to at least one second data block, and a means to transmit each second data block to a designated one of the nodes, a method of learning the routing information in the node comprising the steps of:

searching the table with a destination station address contained in each first data block received from the frontend network;

adding learning indicator information to each second data block, which learning indicator information includes station position information;

transmitting each second data block with said added learning indicator information to a corresponding one of the highways;

receiving each second data block with said added learning indicator information from all of the highways; and

registering said station position information from the learning indicator information of each received second data block into the table.

26. A communication system for interconnecting a plurality of frontend networks with a loop-type backbone network, the communication system comprising:

the backbone network including a plurality of logical or physical highways;

at least one node means connected to the backbone network, said node means including a bridge means connected to a corresponding one of the frontend networks, said bridge means includes

a segment means for segmenting a first data block of variable length received from the frontend network, into second data blocks of fixed length to be transmitted along the backbone network, each of said second data blocks having a destination address field, a source address field, a backbone MAC header field, and a cell content field,

a searching means for searching a routing information table with a destination station address contained in said first data blocks, and

an assembling means for re-assembling said first data block from at least one of said second data blocks received from the backbone network, said assembling means including a receive control means and a reassemble buffer means for buffering reassembled said first data block, and said receive control means having means for storing a group broadcast information and means for selectively receiving broadcasted second data blocks in accordance with said destination field and said group broadcast information; and

,

a switching means for selectively connecting said bridge means to at least one of said backbone network highways to transmit said second data block along the backbone network.