Extended domain computer network using standard links

• US 5,617,421 A
• Filed: 06/17/1994
• Issued: 04/01/1997
• Est. Priority Date: 06/17/1994
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Systems, Inc.
• Inventors: Scott, Frederick, Chin, Hon W.
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): TON, DANG T
• Application Number:
  US08/261,393
• Time in Patent Office: 1,019 Days
• Field of Search: 370/85.15, 370/94.1, 370/94.2, 370/94.3, 370/60, 370/60.1, 370/61, 370/85.5, 370/85.6, 395/200.01, 395/200.1, 340/825.02, 340/825.03, 340/825.51, 340/825.52
• US Class Current: 370/402
• CPC Class Codes: H04L 12/1854 with non-centralised forwarding system, e.g. chaincast
• CPC Class Codes: H04L 12/4641 Virtual LANs, VLANs, e.g. virtual private networks [VPN] LAN interconnection over a bridge based backbone H04L12/462; encapsulation techniques H04L12/4633; routing of packets H04L45/00; packet switches H04L49/00; virtual private networks for security H04L63/0272

Abstract

A method for establishing and maintaining virtual network domains in a segmented computer network having a first domain and a second domain. A first table entry for a first endstation in a first forwarding table of a first switching fabric circuit is created. The first table entry includes domain information specifying that the first endstation is in the first domain and port information specifying that the first endstation is coupled to a first port. A packet having the first endstation as a source is received by the first port of the first switching fabric circuit, and a destination for the packet is determined. If the packet specifies a second endstation of the first domain as the destination, the packet is forwarded to the second endstation. If the destination for the packet specifies more than one endstation, the domain of the source of the packet is determined, and the packet is forwarded to the specified endstations of the first domain. For a second embodiment, source and destination information are compared to determine forwarding information for a packet, and the packet is forwarded as specified by the forwarding information. For a third embodiment, intelligent selection between multiple paths to the same endstation is provided by the comparison of source and destination forwarding information.

Claims

1. In a segmented computer network having a first domain and a second domain, a method comprising the steps of:

creating a first table entry for a first endstation in a first forwarding table of a first switching fabric circuit, the first table entry including domain information specifying that the first endstation is in the first domain and port information specifying that the first endstation is coupled to a first port;

receiving a packet having the first endstation as a source by the first port of the first switching fabric circuit;

determining a destination for the packet;

forwarding the packet to a second endstation of the first domain if the packet specifies the second endstation as the destination;

determining the domain information of the source if the destination for the packet specifies more than one endstation; and

forwarding the packet to endstations of the first domain as specified by the domain information of the source.

2. The method of claim 1, wherein the step of creating the first table entry comprises the steps of:

creating a second table entry for the first endstation in a second forwarding table of a second switching fabric circuit, the second table entry including domain information specifying that the first endstation is in the first domain and port information specifying that the first endstation is coupled to a second port;

sharing the second table entry with the first switching fabric circuit via an interswitch link coupled between the second switching fabric circuit and the first port of the first switching fabric circuit; and

updating the first forwarding table to include the first table entry.

3. The method of claim 2, wherein the step of sharing the second table entry comprises the steps of:

creating a packet of forwarding information by a first switching processor of the second switching fabric circuit, the packet of forwarding information including table entries of the second forwarding table; and

forwarding the packet of forwarding information to a second switching processor of the first switching fabric circuit via the interswitch link.

4. The method of claim 2, wherein the interswitch link is a standard local area network (LAN) segment, the step of sharing the second table entry comprising the step of:

sending a standard LAN packet to the first port of the first switching fabric circuit via the interswitch link.

5. The method of claim 1, wherein the first port is in the first and second domains.

6. The method of claim 1, wherein the domain information and the port information of the first endstation is included in a first port of exit mask.

7. The method of claim 1, wherein the method further comprises the steps of:

determining the domain information of the source if the packet specifies an unknown destination; and

forwarding the packet to endstations of the first domain as specified by the domain information of the source.

8. The method of claim 1, wherein the step of creating the first table entry in the first forwarding table comprises the steps of:

receiving forwarding information from a network management endstation coupled to the segmented network, the forwarding information including domain information specifying that the first endstation is in the first domain and port information specifying that the first endstation is coupled to the first port; and

updating the first forwarding table to include the forwarding information.

9. In a segmented computer network having a first domain and a second domain, a method comprising the steps of:

receiving a broadcast packet by a first port of a first switching fabric circuit from a first local area network (LAN) segment that operates according to a LAN standard protocol;

forwarding the broadcast packet to a second switching fabric circuit via an interswitch link by the first switching fabric circuit, wherein the interswitch link operates according to the LAN standard protocol;

receiving the broadcast packet by the second switching fabric circuit;

determining domain information of the broadcast packet by the second

switching fabric circuit performing a look-up of a source address of the broadcast packet;

forwarding the broadcast packet to ports of the second switching fabric circuit by the second switching fabric circuit in response to the domain information such that the broadcast packet is forwarded to ports of the first domain if the domain information indicates that the source address of the broadcast packet is of the first domain and such that the broadcast packet is forwarded to ports of the second domain if the domain information indicates that the source address of the broadcast packet is of the second domain.

10. The method of claim 9, wherein the source address identifies a first endstation, the step of determining domain information comprising the steps of:

creating a first table entry for a first endstation in a first forwarding table of the first switching fabric circuit, the first table entry including domain information specifying that the first endstation is in the first domain;

sharing the first table entry with the second switching fabric circuit via the interswitch link;

creating a second table entry for the first endstation in a second forwarding table of the second switching fabric circuit, the second table entry including domain information specifying that the first endstation is in the first domain; and

performing a look-up of the second forwarding table by the second switching fabric circuit to determine the domain information of the first endstation.

11. The method of claim 10, wherein the step of sharing the first table entry comprises the steps of:

creating a packet of forwarding information by a first switching processor of the first switching fabric circuit, the packet of forwarding information including table entries of the second forwarding table; and

forwarding the packet of forwarding information to a second switching processor of the second switching fabric circuit via the interswitch link.

12. The method of claim 10, the step of sharing the first table entry comprising the step of:

sending a standard LAN packet to the first port of the first switching fabric circuit via the interswitch link, wherein the domain information of the first endstation is included in a data field of the standard LAN packet.

13. The method of claim 10, wherein the second table entry includes a port of exit mask specifying at least one port of the second switching fabric circuit to which the broadcast packet is forwarded by the second switching fabric circuit.

14. The method of claim 9, wherein the broadcast packet is an implied broadcast packet, the implied broadcast packet being a unicast packet specifying an unknown destination.

15. The method of claim 9, wherein the first port is in the first and second domains.

16. The method of claim 9, wherein the method further comprises the steps of:

determining the domain information of the source if the packet specifies an unknown destination; and

forwarding the packet to endstations of the first domain as specified by the domain information of the source.

17. The method of claim 9, wherein the step of creating the first table entry in the first forwarding table comprises the steps of:

receiving forwarding information from a network management endstation coupled to the segmented network, the forwarding information including domain information specifying that the first endstation is in the first domain and port information specifying that the first endstation is coupled to the first port; and

updating the first forwarding table to include the forwarding information.

18. A segmented computer network comprising:

an interswitch link, wherein the interswitch link operates according to a local area network (LAN) standard protocol;

a plurality of LAN segments that operate according to the LAN standard protocol;

a plurality of endstations coupled to the LAN segments;

a first switching fabric circuit, the first switching fabric circuit including a first port connected to the interswitch link, a second port coupled to at least one endstation via a first LAN segment and specified as being in a first domain, and a third port coupled to at least one endstation, via a second LAN segment and specified as being in a second domain, the first switching fabric circuit for forwarding a first packet to a port specified by a destination address field of the first packet if the first packet is a unicast packet, the first switching fabric circuit for forwarding the first packet to a port specified by domain information determined from a source address field of the first packet such that isolation between the first and second domains is maintained if the first packet is a broadcast packet;

a second switching fabric circuit, the second switching fabric circuit including a fourth port connected to the interswitch link and a fifth port coupled to at least one endstation via a third LAN segment and specified as being in the first domain.

19. The segmented computer network of claim 18, wherein the first switching fabric circuit comprises:

a first forwarding table for maintaining table entries for each endstation, wherein each table entry includes domain information for each endstation; and

a first processor, coupled to the first forwarding table, for performing look-ups in the first forwarding table.

20. The segmented computer network of claim 19, wherein the second switching fabric circuit comprises:

a second forwarding table for maintaining table entries for each endstation, wherein each table entry includes domain information for each endstation; and

a second processor, coupled to the second forwarding table, for performing look-ups in the second forwarding table.

21. The segmented computer network of claim 20, wherein the second processor shares table entries of the second forwarding table with the first switching fabric circuit, the second processor for creating a standard LAN packet according to the standard LAN protocol, the standard LAN packet including at least one table entry of the second forwarding table in a data field of the standard LAN packet, the second processor for sending the standard LAN packet to the first switching fabric circuit via the interswitch link.

22. The segmented computer network of claim 21, wherein the second switching fabric circuit includes a sixth port specified as being in the first and second domains.

23. The segmented computer network of claim 18, wherein the first switching fabric circuits equivalently processes broadcast packets, multicast packets, and unicast packets specifying unknown destinations.

24. In a segmented computer network having a first domain and a second domain, a method comprising the steps of:

receiving a packet by a first port of a first switching fabric circuit, the packet including a source address field and a destination address field;

performing a look-up on the destination address field to retrieve destination information for a destination, the destination information including a destination port of exit mask;

performing a look-up on the source address field to retrieve source information for a source, the source information including a source port of exit mask;

comparing the source information to the destination information to produce forwarding information by performing a logical AND operation using the source port of exit mask and the destination port of exit mask as operands to produce a final port of exit mask, the packet being forwarded as specified by the final port of exit mask; and

forwarding the packet to at least one port as specified by the forwarding information.

25. The method of claim 24, wherein the destination information further comprises an indicator bit for specifying that the step of comparing the source information to the destination information is to be performed only when the indicator bit is in a first state.

26. A segmented computer network comprising:

an interswitch link, wherein the interswitch link operates according to a local area network (LAN) standard protocol;

a plurality of LAN segments that operate according to the LAN standard protocol;

a plurality of endstations coupled to the LAN segments;

a first switching fabric circuit including a first port connected to the interswitch link, a second port coupled to at least one endstation via a first LAN segment and specified as being in a first domain, and a third port coupled to at least one endstation via a second LAN segment and specified as being in a second domain, the first switching fabric circuit for forwarding a first packet received from the first port to at least one port specified by comparing domain information determined from a source address of the first packet to domain information determined from a destination address of the first packet such that isolation between the first and second domains is maintained; and

a second switching fabric circuit, the second switching fabric circuit including a fourth port connected to the interswitch link and a fifth port coupled to at least one endstation via a third LAN segment and specified as being in the first domain, the second switching fabric circuit for sending the first packet.

27. The segmented computer network of claim 26, wherein the first switching fabric circuit comprises:

a first forwarding table for maintaining table entries for each endstation, wherein each table entry includes domain information for each endstation; and

a first processor, coupled to the first forwarding table, for determining domain information by performing look-ups in the first forwarding table.

28. The segmented computer network of claim 27, wherein the second switching fabric circuit comprises:

a second forwarding table for maintaining table entries for each endstation, wherein each table entry includes domain information for each endstation; and

a second processor, coupled to the second forwarding table, for determining domain information by performing look-ups in the second forwarding table.

29. The segmented computer network of claim 28, wherein the second processor shares table entries of the second forwarding table with the first switching fabric circuit, the second processor for creating a standard LAN packet according to the standard LAN protocol, the standard LAN packet including at least one table entry of the second forwarding table in a data field of the standard LAN packet, the second processor for sending the standard LAN packet to the first switching fabric circuit via the interswitch link.

30. The segmented computer network of claim 29, wherein the second switching fabric circuit includes a sixth port specified as being in the first and second domains.

31. The segmented computer network of claim 29, wherein each table entry comprises a port of exit mask.

32. The segmented computer network of claim 31, wherein performing look-ups based on the destination address field of the first packet results in a destination port of exit mask that specifies at least one port of the first switching fabric circuit to which the first packet is to be forwarded.

33. The segmented computer network of claim 32, wherein performing a look-up based on the source address field of the first packet results in a source port of exit mask that specifies at least one port of the first switching fabric circuit to which broadcasts packets originating from an endstation having the source address are forwarded.

34. The segmented computer network of claim 33, wherein the first switching fabric circuit compares the domain information of the destination address to the domain of the source address by performing a logical AND operation using the source port of exit mask and the destination port of exit mask as operands.

35. The segmented computer network of claim 34, wherein the first packet is a multicast packet specifying less than all the ports of the first switching fabric circuit that are included in the first domain.

36. The segmented computer network of claim 34, wherein the first packet is a unicast packet having a destination address that is not globally unique.

37. In a segmented computer network, a method comprising the steps of:

creating a table entry for a first endstation in a forwarding table of a first switching fabric circuit, the table entry including destination forwarding information specifying a first path to the first endstation and a second path to the first endstation, wherein the endstation is coupled to a second switching fabric circuit;

receiving a packet by a first port of the first switching fabric circuit, the packet including a source address field and a destination address field, the destination address field specifying the first endstation as a destination for the packet;

performing a look-up on the destination address field to retrieve the destination forwarding information for the first endstation;

performing a look-up on the source address field to retrieve source forwarding information of a source of the packet;

comparing the source forwarding information to the destination forwarding information to produce final forwarding information, wherein the final forwarding information specifies only one of the first and second paths;

forwarding the packet to the first endstation via the first path if the final forwarding information specifies the first path;

forwarding the packet to the first endstation via the second path if the final forwarding information specifies the second path.

38. The method of claim 37, wherein the destination forwarding information includes a destination port of exit mask and the source forwarding information includes a source port of exit mask.

39. The method of claim 38, wherein the step of comparing the source forwarding information to the destination forwarding information comprises the step of performing a logical AND operation using the source port of exit mask and the destination port of exit mask as operands to produce a final port of exit mask, the packet being forwarded as specified by the final port of exit mask.

40. The method of claim 39, wherein the destination forwarding information further comprises an indicator bit for specifying that the step of comparing the source forwarding information to the destination forwarding information is to be performed only when the indicator bit is in a first state.

41. The method of claim 37, wherein the destination forwarding information further comprises an indicator bit for specifying that the step of comparing the source forwarding information to the destination forwarding information is to be performed only when the indicator bit is in a first state.

42. A segmented computer network comprising:

a first interswitch link;

a second interswitch link;

a first switching fabric circuit including a first port connected to the first interswitch link, a second port coupled to the second interswitch link, and a third port coupled to a first endstation; and

a second switching fabric circuit including a fourth port coupled to the first interswitch link, a fifth port coupled to the second interswitch link, and a sixth port coupled to a second endstation, the second switching fabric circuit for creating a table entry for the first endstation in a forwarding table, the table entry including destination forwarding information specifying the first interswitch link as a first path to the first endstation and the second interswitch link as a second path to the first endstation, for receiving a packet from the second endstation, the packet including a source address field and a destination address field, the destination address field specifying the first endstation as a destination for the packet, for performing a look-up on the destination address field to retrieve the destination forwarding information for the first endstation, for performing a look-up on the source address field to retrieve source forwarding information of the second endstation, for comparing the source forwarding information to the destination forwarding information to produce final forwarding information, wherein the final forwarding information specifies only one of the first and second paths, and for forwarding the packet to the first endstation in response to the final forwarding information.

43. The method of claim 42, wherein the destination forwarding information includes a destination port of exit mask and the source forwarding information includes a source port of exit mask.

44. The segmented computer network of claim 43, wherein the second switching fabric circuit compares the source forwarding information to the destination forwarding information by performing a logical AND operation using the source port of exit mask and the destination port of exit mask as operands.