Hierarchical label distribution for inter-area summarization of edge-device addresses
A system and method are provided for separately distributing edge-device labels and routing information across routing areas of a computer network. Because the edge-device labels are distributed separately from network routing information, the process of distributing the edge-device labels does not preclude conventional edge-device address summarizations. Illustratively, a novel “label mapping” LSA is employed for distributing the edge-device labels across routing areas. The label-mapping LSA may be embodied as an area-scope OSPF opaque LSA (type 10) or an IS-IS LSP containing TLVs of area scope. Advantageously, the present invention is generally applicable whenever label values are allocated to edge devices in a multi-area computer network and data is “tunneled” through the network from one edge device to another.
1. A method for distributing edge-device labels between first and second routing areas of a computer network, the computer network containing one or more edge devices that are reachable in the first routing area, the method comprising:
identifying, in the first routing area, an edge-device address for each of the one or more edge devices;
storing the identified edge-device addresses in a first message;
distributing the first message in the second routing area to advertise, in the second routing area, the identified edge-device addresses;
allocating a different edge-device label value for each identified edge-device address;
storing the identified edge-device addresses and their corresponding edge-device label values in a second message; and
distributing the second message in the second routing area to advertise, in the second routing area, the identified edge-device addresses and their corresponding edge-device label values.
2. The method of claim 1 , wherein the step of distributing the first message in the second routing area to advertise the identified edge-device addresses further comprises:
summarizing the identified edge-device addresses; and
advertising the summarized edge-device addresses in the second routing area.
3. The method of claim 1 , wherein the second message is formatted as an Open Shortest Path First (OSPF) opaque link-state advertisement.
4. The method of claim 1 , wherein the second message is formatted as an Intermediate-System-to-Intermediate-System (IS-IS) link-state packet including a type-length-value (TLV) tuple configured to store the identified edge-device addresses and their corresponding edge-device label values.
5. The method of claim 1 wherein the first message is an Open Shortest Path First (OSPF) Summary link-state advertisement.
6. The method of claim 1 , wherein the computer network is configured as a network selected from a group consisting of:
a layer-2 virtual private network (L2VPN), a layer-3 VPN (L3VPN), a pseudowire edge-to-edge emulation (PWE3) based network, an Internet Protocol (IP) over Multi-Protocol Label Switching (MPLS) based network, a VPNv6 over MPLS based network, a BGP3 core network and a Request For Comments (RFC)-2547 based network.
7. The method of claim 1 , further comprising:
forwarding data packets in the second routing area using at least one of the edge-device labels distributed in the second routing area.
8. An area border device situated between first and second routing areas in a computer network, one or more edge devices being reachable in the first routing area, the area border device comprising:
a processor;
a first network interface adapted to communicate in the first routing area, the first network interface being configured to receive an edge-device address for each of the one or more edge devices that are reachable in the first routing area;
a second network interface adapted to communicate in the second routing area; and
a memory adapted to store instructions which are executable by the processor for performing the steps of:
advertising a first message over the second network interface, the first message containing the edge-device addresses received at the first network interface;
allocating a different edge-device label value for each received edge-device address; and
advertising a second message over the second network interface, the second message containing the edge-device addresses and their corresponding edge-device label values.
9. The area border device of claim 8 , wherein the memory further comprises instructions for performing the steps of:
summarizing the received edge-device addresses;
storing the summarized edge-device addresses in the first message; and
advertising the first message containing the summarized edge-device addresses over the second network interface.
10. The area border device of claim 8 , wherein the second message is formatted as an Open Shortest Path First (OSPF) opaque link-state advertisement.
11. The area border device of claim 8 , wherein the second message is formatted as an Intermediate-System-to-Intermediate-System (IS-IS) link-state packet including a type-length-value (TLV) tuple configured to store the identified edge-device addresses and their corresponding edge-device label values.
12. The area border device of claim 8 , wherein the first message is an Open Shortest Path First (OSPF) Summary link-state advertisement.
13. The area border device of claim 8 , wherein the second network interface is further configured to receive a data packet containing a particular edge-device label value and the memory further comprises instructions for:
performing a label-lookup operation based on the received data packet's particular edge-device label value; and
forwarding the received data packet over the first network interface in response to the label-lookup operation.
14. The area border device of claim 8 , wherein the area border device is an area border router.
15. An area border device situated between first and second routing areas in a computer network, one or more edge devices being reachable in the first routing area, the area border device comprising:
means for receiving an edge-device address for each of the one or more edge devices that are reachable in the first routing area;
means for storing the identified edge-device addresses in a first message;
means for distributing the first message in the second routing area to advertise, in the second routing area, the received edge-device addresses;
means for allocating a different edge-device label value for each received edge-device address; and
means for storing the identified edge-device addresses and their corresponding edge-device label values in a second message;
means for distributing the second message in the second routing area to advertise, in the second routing area, the received edge-device addresses and their corresponding edge-device label values.
16. A computer network, comprising:
a first routing area through which one or more edge devices are reachable;
a second routing area coupled to the first routing area;
means for identifying, in the first routing area, an edge-device address for each of the one or more edge devices;
means for storing the identified edge-device addresses in a first message;
means for distributing the first message in the second routing area to advertise, in the second routing area, the identified edge-device addresses;
means for allocating a different edge-device label value for each identified edge-device address; and
means for storing the identified edge-device addresses and their corresponding edge-device label values in a second message;
means for distributing the second message in the second routing area to advertise, in the second routing area, the identified edge-device addresses and their corresponding edge-device label values.
17. The computer network of claim 16 , further comprising:
means for summarizing the identified edge-device addresses; and
means for advertising the summarized edge-device addresses in the second routing area.
18. The computer network of claim 16 , further comprising:
means for forwarding data packets in the second routing area using at least one of the edge-device labels distributed in the second routing area.
19. A computer-readable medium storing instructions for execution on a processor for the practice of a method of distributing edge-device labels between first and second routing areas of a computer network, the computer network containing one or more edge devices that are reachable in the first routing area, the method comprising:
identifying, in the first routing area, an edge-device address for each of the one or more edge devices;
storing the identified edge-device addresses in a first message;
distributing the first message in the second routing area to advertise, in the second routing area, the identified edge-device addresses;
allocating a different edge-device label value for each identified edge-device address;
storing the identified edge-device addresses and their corresponding edge-device label values in a second message; and
distributing the second message in the second routing area to advertise, in the second routing area, the identified edge-device addresses and their corresponding edge-device label values.
20. An apparatus comprising:
a processor;
a first network interface operable to communicate into a first routing area and to receive an edge-device address for one or more edge devices that are reachable in the first routing area;
a second network interface operable to communicate into a second routing area; and
a memory operable to store instructions that when executed by the processor,
summarize edge device addresses,
send a first link-state advertisement over the second network interface, the first link-state advertisement containing the summarized edge device addresses,
associate an edge-device label value to each received edge-device address, and
send a second link-state advertisement over the second network interface, the second link-state advertisement mapping the edge-device addresses to their associated edge-device label values.
21. The apparatus of claim 20 , wherein the second link-state advertisement is formatted as an Open Shortest Path First (OSPF) opaque link-state advertisement.
22. The apparatus of claim 20 , wherein the second link-state advertisement is configured to have an area-wide scope that prevents the link-state advertisement from being sent beyond the routing area into which it is initially sent.
23. The apparatus of claim 20 , wherein first link-state advertisement is an Open Shortest Path First (OSPF) Summary link-state advertisement.
24. The apparatus of claim 20 , wherein the instructions that when executed by the processor summarize edge device addresses operate to aggregate the edge device addresses by consolidating ranges of addresses.