Packet forwarding in a network

1. A method of providing packet routing information, the method comprising:

encoding routing information from a source node to one or more destination nodes into a compact representation of set membership;

wherein the routing information comprises representations of one or more identifiers, each identifier identifying a respective network link, a respective node, or a full or partial path containing two or more network links; and

wherein the method comprises generating d candidate compact representations of set membership from d representations of the one or more identifiers, where d is an integer greater than one, and putting one of the candidate compact representations of set membership into a header of a packet that is to be sent from the source node to the destination node(s).

2. The method as claimed in claim 1 wherein the routing information is encoded at the source node or at a routing server.

3. The method as claimed in claim 1 and further comprising:

including, in the packet header, information identifying the compact representation of set membership included in the packet header.

4. A method of routing a packet through a network, the method comprising:

receiving the packet at a network node;

interrogating routing information contained in a header of the packet as a compact representation of set membership to determine one or more links along which the packet is to be sent from the network node and/or to determine one or more other nodes to which the packet is to be sent from the network node; and

forwarding the packet along the determined link(s) and/or to the determined other node(s);

wherein the routing information comprises one of a plurality of candidate representations of one or more identifiers, each identifier identifying a respective network link, a respective node, or a full or partial path containing two or more network links; and

wherein the routing further comprises selecting, from d look-up tables each corresponding to one of d candidate representations of the one or more identifiers, where d is an integer greater than one, a look-up table corresponding to the received representation of the one or more identifiers.

5. A network node for providing routing information for packets, the network node being adapted to encode the routing information from a source node to one or more destination nodes into a compact representation of set membership for inclusion into a header of a packet that is to be sent from the source node to the destination node(s), the routing information comprising representations of one or more identifiers;

wherein the network node is adapted to encode the routing information by:

generating d representations of at least some of the one or more identifiers, where d is an integer greater than one;

generating d candidate compact representations of set membership from the d representations of the one or more identifiers; and

selecting one of the candidate compact representation of set membership.

6. The network node as claimed in claim 5 and adapted to encode routing information comprising representations of one or more identifiers by:

generating d representations of at least some of the identifiers, where d is an integer greater than one;

generating d candidate compact representations of set membership from the d representations of the identifiers; and

sending two or more of the candidate compact representations of set membership to another node.

7. The method as claimed in claim 1 wherein each of the d candidate compact representations of set membership from d representations includes two or more of the one or more identifiers forming a complete path from the source node to the one or more destination nodes.

8. The method as claimed in claim 1 wherein generating the d candidate compact representations of set membership from d representations includes generating each d candidate compact representation of set membership such that all representations of the one or more identifiers that form a complete path of the respective candidate compact representation of set membership from the source node to the one or more destination nodes can be matched with a portion of the candidate compact representation of set membership.

9. The method as claimed in claim 8 wherein generating d candidate compact representations of set membership from d representations further includes logically combining a representation of a respective candidate compact representation of set membership with each representation of the one or more identifiers that form the complete path of the respective candidate compact representation of set membership to form the respective candidate compact representation as a composite of the representations of the one or more identifiers that form the complete path.

10. The method as claimed in claim 9 wherein logically combining includes performing a logical OR on the representation of the respective candidate compact representation of set membership and each representation of the one or more identifiers that form the complete path of the respective candidate compact representation of set membership.

11. The method as claimed in claim 1 wherein each of the d candidate compact representations of set membership indicates a match to a selected identifier by logically filtering the respective candidate compact representation of set membership with the representation of the selected identifier.

12. The method as claimed in claim 11 wherein logically filtering includes performing a logical AND on the respective candidate compact representation of set membership and the representation of the selected identifier.

13. The method as claimed in claim 1 wherein the one of the d candidate compact representations of set membership comprises a bloom filter.

14. The method as claimed in claim 1 further comprising:

optimizing d to reduce false positives.

15. The method as claimed in claim 1 wherein each of the one or more identifiers of a respective d candidate compact representation of set membership has d representations.

16. The method as claimed in claim 4 wherein interrogating routing information includes logically filtering a respective candidate compact representation of set membership with the received representation.

17. The method as claimed in claim 16 wherein logically filtering includes performing a logical AND on the respective candidate compact representation of set membership and the received representation to indicate if the received representation is a match of at least a portion of the respective candidate compact representation.