Token ring bridge distributed in a switched fabric

• US 6,563,832 B1
• Filed: 03/10/1999
• Issued: 05/13/2003
• Est. Priority Date: 11/30/1998
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Decker, Eric, Campbell, Randall G., Lingle, Kevin R., Stuart, Carson, Cartee, Claude Alan, Potter, Kenneth H. Jr., Carroll, David A., Kidd, Jeffrey W., Adams, Kara J.
• Primary Examiner(s): Jung, Min
• Application Number:
  US09/266,239
• Time in Patent Office: 1,525 Days
• Field of Search: 370/401, 370/402, 370/403, 370/404, 370/405, 370/406, 370/407, 370/408, 370/450, 370/451, 370/452, 370/463, 370/254, 370/255, 370/256, 370/257, 370/258
• US Class Current: 370/403
• CPC Class Codes: H04L 12/417 with deterministic access, e.g. token passing
• CPC Class Codes: H04L 12/433 with asynchronous transmission, e.g. token ring, register insertion
• CPC Class Codes: H04L 12/46 Interconnection of networks
• CPC Class Codes: H04L 12/4604 LAN interconnection over a backbone network, e.g. Internet, Frame Relay
• CPC Class Codes: H04L 12/462 LAN interconnection over a bridge based backbone
• CPC Class Codes: H04L 12/467 Arrangements for supporting untagged frames, e.g. port-based VLANs
• CPC Class Codes: H04L 12/4695 VTP [VLAN trunking protocol]

Abstract

A distributed token ring (TR) bridge has a logical switch fabric that is distributed over a TR switching network of switches interconnected by trunk links. The distributed TR bridge includes a plurality of TR switches, each having a Bridge Relay Function (BRF) logically coupled to at least one Concentrator Relay Function (CRF). Distribution of the switch fabric essentially comprises logically distributing the BRF function among the network of switches.

Claims

1. A distributed token ring (TR) bridge comprising:

at least one trunk link;

a plurality of switches coupled to the trunk link, each switch including (i) token ring port interface circuitry organized as at least one Concentrator Relay Function (CRF) to connect to a plurality of token ring local area networks and (ii) trunk interface circuitry interconnected between the port interface circuitry and the trunk link, the interconnected trunk interface circuitry further organized as a Bridge Relay Function (BRF) that is distributed among the plurality of switches to create a single logical switch fabric to interconnect token ring local area networks.

2. The distributed TR bridge of claim 1 wherein the port interface circuitry comprises:

a first device that provides service layer for moving frames to and from TR media segments; and

a second device coupled to the first device, the second device configured to perform data buffering and frame manipulation operations.

3. The distributed TR bridge of claim 2 wherein the first device is a quad medium access control (QM) device having a plurality of TR ports and wherein the second device is a quad switch fabric interface (QS) device that services the plurality of TR ports via the QM device.

4. The distributed TR bridge of claim 3 wherein the trunk interface circuitry comprises:

a third device that provides a service layer for moving frames to and from the trunking link; and

a fourth device coupled to the third device, the fourth device configured to perform data buffering and frame manipulation operations.

5. The distributed TR bridge of claim 4 wherein the third device is a medium access control (MAC) interface circuit coupled to the trunk link and wherein the fourth device is a switch fabric interface (SF) device.

6. The distributed TR bridge of claim 5 further comprising a virtual local area network (VLAN) table coupled to the SF device, the VLAN table used by the SF device to acquire information such as CRF VLAN identifiers (IDs) pertaining to frames flowing through the device.

7. The distributed TR bridge of claim 6 further comprising:

a modified forwarding table coupled to each of the QS and SF devices, the modified forwarding table used by the devices to select destination ports for receiving the frames; and

a CRF table coupled to each of the QS and SF devices, the CRF table providing information such as a VLAN ID corresponding to a CRF ring number.

30. A computer readable media, comprising:

instructions for execution on a processor for the practice of the method of claim 1 or claim 24.

31. Electromagnetic signals propagating on a computer network, comprising:

the electromagnetic signals carrying instructions for execution on a processor for the practice of the method of claim 1 or claim 24.

8. A method for distributing a token ring (TR) bridge among a plurality of switches interconnected by trunk links, each switch including port interface circuitry having a plurality of ports for receiving incoming frames from a plurality of TR segments connected to the ports, each switch further including trunk interface circuitry connected to the trunk links, the method comprising the steps of:

organizing (i) the port interface circuitry as a plurality of Concentrator Relay Functions (CRFs), the CRFs each having a plurality of ports, and each port to connect to a token ring local area network and (ii) the trunk interface circuitry as a Bridge Relay Function (BRF) to interconnect token ring local area networks;

coupling the BRF to the CRFs; and

distributing the BRF among the interconnected switches to create a single logical switch fabric that facilitates switching of frames among the ports of a CRF and bridging of the frames between CRFs coupled to the BRF.

9. The method of claim 8 further comprising the step of:

parsing each incoming frame at the interface circuitry to compute information such as destination and source virtual local area network (VLAN) identifiers (IDs) along with destination and source addresses for the frame; and

executing frame forwarding operations for the incoming frame at the interface circuitry using the computed information, the frame forwarding operations comprising source learning and forwarding decision operations.

10. The method of claim 9 wherein the step of parsing further comprises the step of processing each incoming frame depending upon a type of the frame forwarded by the interface circuitry.

11. The method of claim 10 wherein the types of frames include Non-Source Route (NSR), All Routes Explorer (ARE), Spanning Tree Explorer (STE) and Specifically Routed Frame (SRF).

12. The method of claim 11 wherein the step of processing comprises the step of, if the frame has an ARE, STE or SRF frame type:

analyzing contents of a routing information field (RIF) of the frame at the port interface circuitry prior to computing the source and destination addresses and VLAN IDs.

13. The method of claim 12 wherein the step of processing comprises step of, if the frame is an NSR frame type:

determining a bridging type of the distributed bridge prior to computing the source and destination addresses and VLAN IDs.

14. The method of claim 13 wherein, for source learning operations, the step of executing comprises the steps of:

accessing a modified forwarding table having a plurality of entries using a combination of the computed source VLAN ID and source address; and

determining whether the combination is stored in the modified forwarding table.

15. The method of claim 14 wherein the step of determining whether the combination is stored in the modified forwarding table comprises the steps of:

if an entry is not found in the table that matches the combination, creating a new entry containing the source VLAN ID, the source address and an inbound port number; and

,

marking a state of a remote/local bit of the entry as local.

16. The method of claim 14 wherein the step of determining whether the combination is stored in the modified forwarding table comprises the steps of:

if an entry is found that matches the combination, checking a state of a remote/local bit to ensure that it is marked local;

checking that an inbound port number matches the port number of the port interface circuitry; and

asserting a used bit to prevent the entry from being aged-out.

17. The method of claim 16 wherein, for forwarding decision operations, the step of executing comprises the step of:

if the frame has an ARE or STE frame type, setting a destination port mask to that defined for a specified destination VLAN ID.

18. The method of claim 17 wherein, for forwarding decision operations, the step of executing comprises the steps of:

if the frame has an NSR or SRF frame type, accessing the modified forwarding table to perform a lookup operation using a combination of the computed destination VLAN ID and destination address; and

determining whether the combination is stored in the modified forwarding table.

19. The method of claim 18 wherein the step of determining whether the combination is stored in the modified forwarding table comprises the step of:

if an entry is not found in the table that matches the combination, setting the destination port mask to that defined for the specified destination VLAN.

20. The method of claim 19 wherein the step of determining whether the combination is stored in the modified forwarding table comprises the step of:

if an entry is found that matches the combination and that is marked local, discarding the frame; and

if an entry is found that matches the combination and that is marked remote, setting the destination port mask that defined in the entry.

21. A switch, comprising:

a plurality of token ring ports, each port configured to connect to a token ring local area network;

a trunk port to connect to a trunk link;

a bus;

token ring port interface circuitry, to interface with the plurality of token ring ports and enabling transfer of a frame between any token ring local area networks connected to the plurality of token ring ports, the token ring interface circuitry connected to the bus; and

trunk interface circuitry to interface with the trunk port, the trunk interface circuitry connected to the bus to enable frame switching between the trunk port and any one of the plurality of token ring ports.

22. The switch as in claim 21, further comprising:

the token ring port interface circuitry organizing the plurality of token ring ports as a Concentrator Relay Function (CRF).

23. The switch as in claim 21, further comprising:

the trunk interface circuitry organized as a Bridge Relay Function (BRF) for interoperation with other switches.

24. A method of operating a switch, comprising:

configuring a plurality of token ring ports, each port to connect to a token ring local area network;

configuring a trunk port to connect to a trunk link;

interfacing a token ring port interface circuitry with the plurality of token ring ports and enabling transfer of a frame between any token ring local area networks connected to the plurality of token ring ports, the token ring interface circuitry connected to a bus; and

interfacing a trunk interface circuitry with the trunk port, the trunk interface circuitry connected to the bus to enable frame switching between the trunk port and any one of the plurality of token ring ports.

25. The method as in claim 24, further comprising:

organizing the token ring port interface circuitry to connect the plurality of token ring ports as a Concentrator Relay Function (CRF).

26. The method as in claim 24, further comprising:

organizing the trunk interface circuitry as a Bridge Relay Function (BRF) for interoperation with other switches.

27. A switch, comprising:

a plurality of token ring ports, each port configured to connect to a token ring local area network;

a trunk port to connect to a trunk link;

a bus;

means for interfacing token ring port interface circuitry with the plurality of token ring ports and enabling transfer of a frame between any token ring local area networks connected to the plurality of token ring ports, the token ring interface circuitry connected to the bus; and

means for interfacing trunk interface circuitry with the trunk port, the trunk interface circuitry connected to the bus to enable frame switching between the trunk port and any one of the plurality of token ring ports.

28. A plurality of switches, comprising:

said plurality of switches interconnecting a plurality of token ring local area networks through at least one trunk link, where each switch has,

a plurality of token ring ports, each port configured to connect to a token ring local area network of said plurality of token ring local area networks;

a trunk port to connect to a said at least one trunk link;

a bus;

token ring port interface circuitry, to interface with the plurality of token ring ports and enabling transfer of a frame between any token ring local area networks, of said plurality of token ring local area networks, connected to the plurality of token ring ports, the token ring interface circuitry connected to the bus; and

trunk interface circuitry to interface with the trunk port, the trunk interface circuitry connected to the bus to enable frame switching between the trunk port and any one of the plurality of token ring ports.

29. A method for operating a plurality of switches, comprising:

said plurality of switches interconnecting a plurality of token ring networks, each switch of said plurality of switches operating according the steps of,

at each switch of said plurality of switches, configuring a plurality of token ring ports, each port to connect to a token ring local area network of said plurality of token ring local area networks;

configuring at least one trunk port to connect to at least one trunk link;

interfacing a token ring port interface circuitry with the plurality of token ring ports and enabling transfer of a frame between any token ring local area networks of said plurality of token ring local area networks connected to the plurality of token ring ports, the token ring interface circuitry connected to a bus; and

interfacing a trunk interface circuitry with said at least one trunk port, the trunk interface circuitry connected to the bus to enable frame switching between the trunk port and any one of the plurality of token ring ports, to enable frame switching through said at least one trunk link and between said plurality of token ring local area networks.