Distributed ring protocol and database

• US 6,674,727 B1
• Filed: 03/10/1999
• Issued: 01/06/2004
• 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: Potter, Kenneth H. Jr., Carroll, David A., Adams, Kara J., Fitzgerald, John K., Kramling, Gary William
• Primary Examiner(s): Jung, Min
• Application Number:
  US09/266,241
• Time in Patent Office: 1,763 Days
• Field of Search: 370/401-408, 370/450-452, 370/463, 370/254-258, 370/410, 370/474, 370/476
• US Class Current: 370/254
• 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 12/467 Arrangements for supporting untagged frames, e.g. port-based VLANs

Abstract

A Distributed Ring Protocol (DRiP) arrangement includes a database and protocol for maintaining and distributing information within a distributed token ring (TR) bridge having a logical switch fabric that is distributed over a TR switching network of switches interconnected by trunk links, such as Inters witch Link (ISL) trunks. The DRiP information is used by switches within the ISL switched fabric to determine the status (configured and/or activated) and association (within a switch) of ports of the distributed bridge.

Claims

1. A system for maintaining and distributing information within a distributed token ring (TR) bridge having a logical switch fabric that is distributed over a TR switching network of switches interconnected by trunk links, the system comprising:

a database contained within each switch of the switch fabric, the database including virtual local area network (VLAN) identifiers (IDs) that map to ring numbers and their associated ports within each switch, the database further including indications as to status of the ports mapped to the VLAN IDs; and

a protocol for distributing the information contained in the database among the switches of the fabric, the protocol defining a communication exchange of messages between the switches, wherein the messages comprise periodically-exchanged messages and specifically-issued messages, the specifically-issued messages being exchanged when there is a change in status of any VLAN ID.

2. The system of claim 1 wherein the periodic and specifically-issued message exchanges enable creation of the database within each switch and further ensure coherency of the databases maintained by the switches.

3. The system of claim 2 wherein the ring numbers pertain to Concentrator Relay Functions (CRFs) and their associated ports of the fabric, the ports coupled to physical token rings adapted to attach to end stations and bridges, and wherein the trunk links are interswitch link (ISL) trunk 1.

4. The system of claim 3 wherein the database and protocol cooperate to provide a distributed ring protocol (DRiP) arrangement that limits all routes explorer (ARE) frames received at each switch of the switch fabric, as well as control formation of a virtual CRF loop created by the ISL links of the network.

5. The system of claim 4 wherein the periodically-exchanged and specifically-issued messages comprise advertisement messages and wherein the protocol comprises a plurality of categories of advertisement messages distributed by each switch to advertise the status of VLAN IDs associated with the CRFs.

6. The system of claim 5 wherein one of the plurality of categories of advertisement messages is a configured category pertaining to CRF ports that have no end stations or bridges inserted into their physical rings.

7. The system of claim 6 wherein another of the plurality of categories of advertisement messages is a configured and active category pertaining to CRF ports that have active end stations or bridges inserted into their physical rings.

8. The system of claim 7 wherein each advertisement message comprises:

a version field containing a version number of the message;

a code field having contents that specify a type of message, such as periodically-exchanged or specifically-issued;

a VLAN-info count field containing a number of VLANs advertised in the message; and

a header length field containing a number of bytes of header for the type of message.

9. The system of claim 8 wherein each advertisement message further comprises:

a configuration revision number field containing a sequence number for determining whether an advertisement message has been received by the switches of the logical switch fabric;

a last changed revision number field containing a last revision number of a change associated with an originating medium access control (MAC) address; and

a MAC address field containing an identifier of the switch sending the advertisement message.

10. The system of claim 9 wherein the identifier of the MAC address field comprises an identifier that uniquely identifies an originator of the advertisement message.

11. The system of claim 10 wherein the identifier comprises a MAC address of the originator of the advertisement message.

12. The system of claim 9 wherein each advertisement message further comprises a VLAN-info field for each active or configured CRF on a switch.

13. The system of claim 12 wherein the VLAN-info field comprises:

a V-info-length subfield having contents that specify a length of the VLAN-info field;

a status subfield having contents that specify a status of the CRF as having an active port or as having no active ports, but configured ports; and

an ISL TR VLAN ID subfield that contains a VLAN ID of the CRF.

14. The system of claim 13 wherein the status subfield comprises:

a configured bit adapted to indicate that a port has been assigned to a particular VLAN ID on the switch; and

an active bit adapted to indicate that an endstation is transmitting on the port and ARE reduction can be performed on the port.

15. The system of claim 7 further comprising:

a processing element within each switch; and

software processes executing on the processing element, the software processes comprising (i) a DRiP core element for constructing and maintaining the database utilizing the advertisement messages and (ii) a DRiP platform-specific element configured for advertisement message handling and specific-function notification within each switch.

16. The system of claim 15 wherein the database comprises a plurality entries, each entry assigned on a per VLAN ID basis and indexed by the VLAN ID of a CRF, each entry further containing a plurality of bits comprising:

a shared bit for informing the software processes that the VLAN ID may be shared and/or distributed among multiple switches;

a local active bit indicating the active status of a local CRF port having the VLAN ID;

a local configured bit indicating the configured status of the local CRF port;

a remote active bit indicating the active status of a remote CRF port having the VLAN ID; and

a remote configured bit indicating the configured status of the remote CRF port.

17. The system of claim 16 wherein the remote active and remote configured bits are passed as status bits of a status subfield within the advertisement message.

18. A method for maintaining and distributing information within a distributed token ring (TR) bridge having a logical switch fabric that is distributed over a TR switching network of switches interconnected by trunk links, the method comprising the steps of:

mapping virtual local area network (VLAN) identifiers (IDs) to ring numbers and their associated ports within a database of each switch in the switch fabric;

providing indications in the database as to status of the ports mapped to the VLAN IDs;

distributing the information contained in the database among the switches of the distributed TR bridge using a protocol that defines a communication exchange of messages between the switches, wherein the messages comprise periodically-exchanged messages and specifically-issued messages; and

exchanging the specifically-issued messages when there is a change in status of any VLAN ID.

19. The method of claim 18 further comprising the steps of:

creating the database within each switch using the periodic and specifically-issued message exchanges; and

ensure coherency of the databases maintained by the switches using the periodic and specifically-issued message exchanges.

20. The method of claim 19 further comprising the step of, wherein the periodically-exchanged and specifically-issued messages comprise advertisement messages:

advertising the status of VLAN IDs associated with Concentrator Relay Functions (CRFs) and their ports of the switch fabric in accordance with a plurality of categories of advertisement messages distributed by each switch.

21. A switch apparatus, comprising:

a database contained within said switch, said database holding data to implement a logical switch fabric over a distributed token ring network of switches, said database including virtual local area network (VLAN) identifiers (IDs) that map to token ring network ring numbers and their associated ports within each switch of said network of switches, the database further including indications as to status of the ports mapped to the VLAN IDs; and

a protocol for distributing the information contained in the database among the switches of the fabric, the protocol defining a communication exchange of messages between the switches.

22. The apparatus of claim 21 further comprising:

said messages include periodically-exchanged messages and specifically-issued messages, the specifically-issued messages being exchanged when there is a change in status of any VLAN ID.

23. The apparatus of claim 22 further comprising:

the periodic and specifically-issued message exchanges enable creation of the database within each switch and further ensure coherency of the databases maintained by the switches.

24. The apparatus of claim 21 further comprising:

said ring numbers pertain to Concentrator Relay Functions (CRFs) and their associated ports of the fabric, the ports coupled to physical token rings adapted to attach to endstations and bridges, and wherein the trunk links are interswitch link (ISL) trunk links.

25. The apparatus of claim 21 further comprising:

said database and protocol cooperate to provide a distributed ring protocol (DRiP) arrangement that limits all routes explorer (ARE) frames received at each switch of the switch fabric, as well as control formation of a virtual CRF loop created by interswitch link (ISL) trunk lines of the network.

26. The apparatus of claim 22 further comprising:

said periodically-exchanged and specifically-issued messages include advertisement messages and wherein the protocol includes a plurality of categories of advertisement messages distributed by each switch to advertise the status of VLAN IDs associated with a control formation of a virtual CRF loop created by interswitch link (ISL) trunk lines of the network.

27. The apparatus of claim 26 further comprising:

one of the plurality of categories of advertisement messages is a configured category pertaining to CRF ports that have no endstations or bridges inserted into their physical rings.

28. The apparatus of claim 27 further comprising:

another of the plurality of categories of advertisement messages is a configured and active category pertaining to CRF ports that have active endstations or bridges inserted into their physical rings.

29. The apparatus of claim 26 further comprising:

each advertisement message includes,

a version field containing a version number of the message;

a code field having contents that specify a type of message, such as periodically-exchanged or specifically-issued;

a VLAN-info count field containing a number of VLANs advertised in the message; and

a header length field containing a number of bytes of header for the type of message.

30. The apparatus of claim 26 further comprising:

each advertisement message includes,

a configuration revision number field containing a sequence number for determining whether an advertisement message has been received by the switches of the logical switch fabric;

a last changed revision number field containing a last revision number of a change associated with an originating medium access control (MAC) address; and

a MAC address field containing an identifier of the switch sending the advertisement message.

31. The apparatus of claim 30 further comprising:

the identifier of the MAC address field includes an identifier that uniquely identifies an originator of the advertisement message.

32. The apparatus of claim 30 further comprising:

the identifier includes a MAC address of the originator of the advertisement message.

33. The apparatus of claim 30 further comprising:

each advertisement message further includes a VLAN-info field for each active or configured CRF on a switch.

34. The apparatus of claim 33 further comprising:

the VLAN-info field includes,

a V-info-length subfield having contents that specify a length of the VLAN-info field;

a status subfield having contents that specify a status of the CRF as having an active port or as having no active ports, but configured ports; and

an ISL TR VLAN ID subfield that contains a VLAN ID of the CRF.

35. The apparatus of claim 34 further comprising:

the status subfield includes,

a configured bit adapted to indicate that a port has been assigned to a particular VLAN ID on the switch; and

an active bit adapted to indicate that an endstation is transmitting on the port and ARE reduction can be performed on the port.

36. The apparatus of claim 21 further comprising:

a processing element within each switch; and

software processes executing on the processing element, the software processes including (i) a DRiP core element for constructing and maintaining the database utilizing an advertisement messages and (ii) a DRiP platform-specific element configured for advertisement message handling and specific-function notification within said switch.

37. The apparatus of claim 21 further comprising:

said database includes a plurality of entries, each entry assigned on a per VLAN ID basis and indexed by the VLAN ID of a CRF, each entry further containing a plurality of bits having,

a shared bit for informing the software processes that the VLAN ID may be shared and/or distributed among multiple switches;

a local active bit indicating the active status of a local CRF port having the VLAN ID;

a local configured bit indicating the configured status of the local CRF port;

a remote active bit indicating the active status of a remote CRF port having the VLAN ID; and

a remote configured bit indicating the configured status of the remote CRF port.

38. The apparatus of claim 37 further comprising:

said remote active and remote configured bits are passed as status bits of a status subfield within an advertisement message.

39. A method of operating a switch, comprising:

holding data to implement a logical switch fabric over a distributed token ring network of switches in a database contained within said switch, said database including virtual local area network (VLAN) identifiers (IDs) that ring network ring numbers and their associated ports within each switch of said network of switches, the database further including indications as to status of the ports mapped to the VLAN IDs; and

distributing, using a protocol, the information contained in the database among the switches of the fabric, the protocol defining a communication exchange of messages between the switches.

40. The method of claim 39, further comprising:

mapping said virtual local area network (VLAN) identifiers (IDs) to ring numbers and their associated ports within a database of said switch;

providing indications in the database as to status of the ports mapped to the VLAN IDs;

transmitting the information contained in the database to the switches of a distributed TR bridge using a protocol that defines a communication exchange of messages between the switches, wherein the messages include periodically-exchanged messages and specifically-issued messages; and

exchanging the specifically-issued messages when there is a change in status of any VLAN ID.

41. The method of claim 39, further comprising:

creating said database within said switch using the periodic and specifically-issued message exchanges; and

ensuring coherency of the databases maintained by said switch using the periodic and specifically-issued message exchanges.

42. The method of claim 41, further comprising:

advertising the status of VLAN IDs associated with Concentrator Relay Functions (CRFs) and their ports of said logical switch fabric in accordance with a plurality of categories of advertisement messages distributed by said switch.

43. A switch apparatus, comprising:

means for containing a database within said switch, said database holding data to implement a logical switch fabric over a distributed token ring network of switches, said database including virtual local area network (VLAN) identifiers (IDs) that map to token ring network ring numbers and their associated ports within each switch of said network of switches, the database further including indications as to status of the ports mapped to the VLAN IDs; and

means for distributing, by a protocol, the information contained in the database among the switches of the fabric, the protocol defining a communication exchange of messages between the switches.

44. The apparatus as in claim 43, further comprising:

means for creating said database within said switch using the periodic and specifically-issued message exchanges; and

means for ensuring coherency of the databases maintained by said switch using the periodic and specifically-issued message exchanges.

45. The apparatus as in claim 43, further comprising:

means for advertising the status of VLAN IDs associated with Concentrator Relay Functions (CRFs) and their ports of said logical switch fabric in accordance with a plurality of categories of advertisement messages distributed by said switch.