Method and apparatus for context-based prefix updates in border gateway protocol

• US 20060164995A1
• Filed: 03/14/2005
• Published: 07/27/2006
• Est. Priority Date: 01/27/2005
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Ward, David D., Djernaes, Martin
• Granted Patent: US 7,590,119 B2
• Time in Patent Office: Days
• US Class Current: 370/238
• CPC Class Codes: H04L 45/02 Topology update or discovery
• CPC Class Codes: H04L 45/025 Updating only a limited number of routers, e.g. fish-eye update
• CPC Class Codes: H04L 45/306 Route determination based on the nature of the carried application

Abstract

A method is disclosed for providing context-based routing table updates in Border Gateway Protocol (BGP) hosts. One or more contexts representing distinct routing tables are defined in a BGP host. As part of establishing a BGP session, a particular context of the one or more contexts is advertised to the BGP peer. In response to receiving from the BGP peer a route update message that includes information identifying the particular context, the routing table that is represented by the particular context is updated at the BGP host.

Claims

1. A method of providing routing table updates in Border Gateway Protocol (BGP) hosts, the method comprising the computer-implemented steps of:

defining one or more contexts in computer memory of a BGP host, wherein each context represents a distinct routing table;

as part of establishing a BGP session between said BGP host and a BGP peer, advertising a particular context of said one or more contexts to said BGP peer; and

in response to receiving from said BGP peer a route update message that includes information identifying said particular context, updating, at said BGP host, a particular routing table that is represented by said particular context.

2. A method as recited in claim 1, wherein:

defining one or more contexts includes associating each context of said one or more contexts with a unique context identifier and a unique context description;

advertising said particular context includes sending to said BGP peer a context identifier and a context description associated with said particular context; and

said information, that is included in said route update message, includes said context identifier.

3. A method as recited in claim 2, wherein:

said particular context is a first context;

said context identifier is a first context identifier; and

said route update message includes a context attribute, wherein;

said context attribute is a first BGP PATH attribute, and

the value of said context attribute associates a second BGP PATH attribute with a second context identifier that is associated with a second context of said one or more contexts that is different than said first context.

4. A method as recited in claim 3, wherein said second BGP PATH attribute is a NEXT_HOP attribute.

5. A method as recited in claim 4, wherein:

said particular routing table represented by said first context includes Internet Protocol version 4 (IPv4) address prefixes;

the value of said NEXT_HOP attribute includes an Internet Protocol version 6 (IPv6) address; and

said second context represents a different routing table that includes IPv6 address prefixes.

6. A method as recited in claim 5, wherein:

updating said particular routing table includes storing said IPv6 address; and

further comprising routing a network packet from an IPv4 network to an IPv6 network, wherein routing includes locating said IPv6 address in said different routing table.

7. A method as recited in claim 2, wherein advertising said particular context includes sending said context identifier and said context description to said BGP peer in a BGP CAPABILITIES parameter that is included in a BGP OPEN message.

8. A method as recited in claim 7, wherein advertising said particular context further includes sending a CONTEXT Address Family Identifier (AFI) value which indicates that said BGP host supports processing of routes that are represented by contexts.

9. A method as recited in claim 7, wherein said route update message further includes said CONTEXT AFI value.

10. A method as recited in claim 2, wherein said route update message is a BGP UPDATE message that includes a field for storing said context identifier.

11. A method as recited in claim 2, wherein updating said particular routing table includes:

extracting the value of said context identifier from said route update message;

only if the value of said context identifier matches the value of any context identifier associated with any context in said BGP host, then extracting the rest of the information included in said route update message.

12. A method as recited in claim 2, wherein said context description comprises one of an Address Family Identifier (AFI) that identifies a type of network address, and a Subsequent Address Family Identifier (SAFI) that identifies a type of communication forwarding mechanism.

13. A method as recited in claim 2, further comprising destroying the associations between said one or more contexts and their corresponding context identifiers upon the closing of said BGP session.

14. A method as recited in claim 2, further comprising preserving the associations between said one or more contexts and their corresponding context identifiers across different BGP sessions.

15. A method as recited in claim 1, further comprising:

sending one or more route update messages to said BGP host for updating only routing tables that are represented by contexts that have been advertised by said BGP host as part of establishing said BGP session; and

wherein said route update message for updating said particular routing table is a member of said one or more route update messages.

16. A method as recited in claim 1, wherein each distinct routing table stores a set of routes having address prefixes belonging to the same address family.

17. A method as recited in claim 1, wherein each distinct routing table stores a set of routes having address prefixes belonging to different address families.

18. A method as recited in claim 1, wherein a set of routes is stored in each distinct routing table, wherein each set of routes is used for routing packets that carry a particular type of information.

19. A method as recited in claim 18, wherein said particular type of information includes at least one of video information, audio information, and data information.

20. An apparatus for providing routing table updates in Border Gateway Protocol (BGP) hosts, comprising:

one or more processors; and

one or more stored sequences of instructions which, when executed by said one or more processors, cause said one or more processors to perform;

defining one or more contexts in computer memory of a BGP host, wherein each context represents a distinct routing table;

as part of establishing a BGP session between said BGP host and a BGP peer, advertising a particular context of said one or more contexts to said BGP peer; and

in response to receiving from said BGP peer a route update message that includes information identifying said particular context, updating, at said BGP host, a particular routing table that is represented by said particular context.

21. An apparatus as recited in claim 20, wherein said apparatus is a router.

22. An apparatus for providing routing table updates in Border Gateway Protocol (BGP) hosts, comprising:

means for defining one or more contexts in computer memory of a BGP host, wherein each context represents a distinct routing table;

means for advertising a particular context of said one or more contexts to a BGP peer, wherein said particular context is advertised as part of establishing a BGP session between said BGP host and said BGP peer; and

means for updating, at said BGP host, a particular routing table that is represented by said particular context, wherein said routing table is updated in response to receiving from said BGP peer a route update message that includes information identifying said particular context.

23. A computer-readable medium carrying one or more sequences of instructions for providing routing table updates in Border Gateway Protocol (BGP) hosts, which instructions, when executed by one or more processors, cause the one or more processors to perform:

defining one or more contexts in computer memory of a BGP host, wherein each context represents a distinct routing table;

as part of establishing a BGP session between said BGP host and a BGP peer, advertising a particular context of said one or more contexts to said BGP peer; and

in response to receiving from said BGP peer a route update message that includes information identifying said particular context, updating, at said BGP host, a particular routing table that is represented by said particular context.

24. A computer-readable medium as recited in claim 23, wherein:

the instructions for defining one or more contexts comprise instructions for associating each context of said one or more contexts with a unique context identifier and a unique context description;

the instructions for advertising said particular context comprise instructions for sending to said BGP peer a context identifier and a context description associated with said particular context; and

said information, that is included in said route update message, includes said context identifier.

25. A computer-readable medium as recited in claim 24, wherein:

said particular context is a first context;

said context identifier is a first context identifier; and

said route update message includes a context attribute, wherein;

said context attribute is a first BGP PATH attribute, and

the value of said context attribute associates a second BGP PATH attribute with a second context identifier that is associated with a second context of said one or more contexts that is different than said first context.

26. A computer-readable medium as recited in claim 25, wherein said second BGP PATH attribute is a NEXT_HOP attribute.

27. A computer-readable medium as recited in claim 26, wherein:

said particular routing table represented by said first context includes Internet Protocol version 4 (IPv4) address prefixes;

the value of said NEXT_HOP attribute includes an Internet Protocol version 6 (IPv6) address; and

said second context represents a different routing table that includes IPv6 address prefixes.

28. A computer-readable medium as recited in claim 27, wherein:

the instructions for updating said particular routing table further comprise instructions for storing said IPv6 address; and

the computer-readable medium further comprises instructions which, when executed by the one or more processors, cause the one or more processors to perform routing a network packet from an IPv4 network to an IPv6 network, wherein the instructions for routing comprise instructions for locating said IPv6 address in said different routing table.

29. A computer-readable medium as recited in claim 24, wherein the instructions for advertising said particular context comprise instructions for sending said context identifier and said context description to said BGP peer in a BGP CAPABILITIES parameter that is included in a BGP OPEN message.

30. A computer-readable medium as recited in claim 29, wherein the instructions for advertising said particular context further comprise instructions for sending a CONTEXT Address Family Identifier (AFI) value which indicates that said BGP host supports processing of routes that are represented by contexts.

31. A computer-readable medium as recited in claim 29, wherein said route update message further includes said CONTEXT AFI value.

32. A computer-readable medium as recited in claim 24, wherein said route update message is a BGP UPDATE message that includes a field for storing said context identifier.

33. A computer-readable medium as recited in claim 24, wherein the instructions for updating said particular routing table comprise instructions for performing:

extracting the value of said context identifier from said route update message;

only if the value of said context identifier matches the value of any context identifier associated with any context in said BGP host, then extracting the rest of the information included in said route update message.

34. A computer-readable medium as recited in claim 24, wherein said context description comprises one of an Address Family Identifier (AFI) that identifies a type of network address, and a Subsequent Address Family Identifier (SAFI) that identifies a type of communication forwarding mechanism.

35. A computer-readable medium as recited in claim 24, further comprising instructions which, when executed by the one or more processors, cause the one or more processors to perform destroying the associations between said one or more contexts and their corresponding context identifiers upon the closing of said BGP session.

36. A computer-readable medium as recited in claim 24, further comprising instructions which, when executed by the one or more processors, cause the one or more processors to perform preserving the associations between said one or more contexts and their corresponding context identifiers across different BGP sessions.

37. A computer-readable medium as recited in claim 23, further comprising instructions which, when executed by the one or more processors, cause the one or more processors to perform:

sending one or more route update messages to said BGP host for updating only routing tables that are represented by contexts that have been advertised by said BGP host as part of establishing said BGP session,

wherein said route update message for updating said particular routing table is a member of said one or more route update messages.

38. A computer-readable medium as recited in claim 23, wherein each distinct routing table stores a set of routes having address prefixes belonging to the same address family.

39. A computer-readable medium as recited in claim 23, wherein each distinct routing table stores a set of routes having address prefixes belonging to different address families.

40. A computer-readable medium as recited in claim 23, wherein a set of routes is stored in each distinct routing table, wherein each set of routes is used for routing packets that carry a particular type of information.

41. A computer-readable medium as recited in claim 40, wherein said particular type of information includes at least one of video information, audio information, and data information.