Neighbor-label distribution with label distribution protocol

Patent metadata

Field	Value
Publication number	US-9253084-B2
Application number	US-201414188148-A
Country	US
Kind code	B2
Filing date	Feb 24, 2014
Priority date	Feb 24, 2014
Publication date	Feb 2, 2016
Grant date	Feb 2, 2016

Abstract

Label Distribution Protocol (LDP) extensions are described that enable distribution of neighbor-label mappings for directly connected neighbor routers. A router capable of supporting the LDP extensions distributes neighbor-labels to be used by the router to label switch traffic destined for the directly connected neighbor router irrespective of a hop-by-hop Interior Gateway Protocol (IGP) path determined based on link metrics. In some examples, the neighbor-labels may increase backup coverage, e.g., link protection and/or node protection, in a network that, due to link metrics, does not have a viable loop-free alternate (LFA) path between an ingress router and an egress router of a label switched path (LSP). In other examples, the neighbor-labels may improve load balancing by enabling an ingress router in a first autonomous system (AS) to select a particular remote link on which to send traffic destined for remote routers in a second AS.

First claim

The invention claimed is:

1. A method comprising:
allocating, with a router, neighbor-labels to be used by the router to label switch traffic destined for respective ones of a plurality of neighbor routers directly connected to the router;
distributing, with the router to one or more Label Distribution Protocol (LDP) peer routers of the router, LDP neighbor-label mapping messages indicating mappings between the allocated neighbor-labels and the neighbor routers, wherein each of the LDP peer routers has one of a direct LDP session with the router or a targeted LDP session with the router;
receiving, with the router from one of the LDP peer routers, traffic encapsulated with one of the neighbor-labels; and
forwarding the traffic to one of the neighbor routers based on the one of the neighbor-labels.

2. The method of claim 1 , wherein forwarding the traffic comprises forwarding the traffic to the one of the neighbor routers regardless of metrics associated with a link between the router and the one of the neighbor routers.

3. The method of claim 1 , further comprising installing neighbor-label forwarding state associating the allocated neighbor-labels with links to the neighbor routers in forwarding information of the router.

4. The method of claim 3 , wherein forwarding the traffic to the one of the neighbor routers based on the one of the neighbor-labels comprises label switching the traffic onto the link to the one of the neighbor routers in accordance with the neighbor-label forwarding state for the one of the neighbor-labels.

5. The method of claim 1 , wherein receiving the traffic encapsulated with one of the neighbor-labels comprises receiving the traffic encapsulated with a label stack including a label for a forwarding equivalence class (FEC) destined for the router and the one of the neighbor-labels allocated by the router for the one of the neighbor routers.

6. The method of claim 1 , further comprising negotiating to determine whether each of the LDP peer routers supports neighbor-label procedures, wherein distributing the LDP neighbor-label mapping messages comprises distributing the LDP neighbor-label mapping messages only to the LDP peer routers that support the neighbor-label procedures.

7. The method of claim 6 , wherein negotiating comprises:
sending a neighbor-label capability advertisement to each of the LDP peer routers indicating that the router supports the neighbor-label procedures; and
receiving neighbor-label capability advertisements from at least one of the LDP peer routers indicating support of the neighbor-label procedures,
wherein each of the neighbor-label capability advertisements comprises one of a LDP initialization message or a LDP capability message that includes a neighbor-label capability parameter type-length-value (TLV).

8. The method of claim 1 , wherein each of the LDP neighbor-label mapping messages includes a forwarding equivalence class (FEC) type-length-value (TLV) with a neighbor FEC element type that specifies a FEC destined for one of the neighbor routers, and a label TLV that specifies one of the neighbor-labels mapped to the FEC for the one of the neighbor routers.

9. The method of claim 1 , further comprising, when the router no longer operates as a neighbor to one of the neighbor routers, sending a LDP neighbor-label withdraw message to each of the LDP peer routers indicating to not use the previously distributed neighbor-label mapping for the one of the neighbor routers.

10. The method of claim 9 , further comprising, in response to sending the LDP neighbor-label withdraw message, receiving a LDP neighbor-label release message from each of the LDP peer routers indicating that the LDP peer routers do not need the previously distributed neighbor-label mapping for the one of the neighbor routers.

11. A router comprising one or more processors configured to execute:
a routing engine to allocate neighbor-labels to be used by the router to label switch traffic destined for respective ones of a plurality of neighbor routers directly connected to the router, and distribute, to one or more Label Distribution Protocol (LDP) peer routers of the router, LDP neighbor-label mapping messages indicating mappings between the allocated neighbor-labels and the neighbor routers, wherein each of the LDP peer routers has one of a direct LDP session or a targeted LDP session with the router; and
a forwarding engine to receive traffic encapsulated with one of the neighbor-labels from one of the LDP peer routers, and forward the traffic to one of the neighbor routers based on the one of the neighbor-labels.

12. The router of claim 11 , wherein the forwarding engine forwards the traffic to the one of the neighbor routers regardless of metrics associated with a link between the router and the one of the neighbor routers.

13. The router of claim 11 , wherein the routing engine installs neighbor-label forwarding state associating the allocated neighbor-labels with links to the neighbor routers in forwarding information of the forwarding engine.

14. The router of claim 13 , wherein the forwarding engine label switches the traffic onto the link to the one of the neighbor routers in accordance with the neighbor-label forwarding state for the one of the neighbor-labels in order to forward the traffic to the one of the neighbor routers.

15. The router of claim 11 , wherein the forwarding engine receives the traffic encapsulated with a label stack including a label for a forwarding equivalence class (FEC) destined for the router and the one of the neighbor-labels allocated by the router for the one of the neighbor routers.

16. The router of claim 11 , wherein the routing engine negotiates to determine whether each of the LDP peer routers supports neighbor-label procedures, and only distributes the LDP neighbor-label mapping messages to the LDP peer routers that support the neighbor-label procedures.

17. The router of claim 16 , wherein, to negotiate, the routing engine:
sends a neighbor-label capability advertisement to each of the LDP peer routers indicating that the router supports the neighbor-label procedures; and
receives neighbor-label capability advertisements from at least one of the LDP peer routers indicating support of the neighbor-label procedures,
wherein each of the neighbor-label capability advertisements comprises one of a LDP initialization message or a LDP capability message that includes a neighbor-label capability parameter type-length-value (TLV).

18. The router of claim 11 , wherein each of the LDP neighbor-label mapping messages includes a forwarding equivalence class (FEC) type-length-value (TLV) with a neighbor FEC element type that specifies a FEC destined for one of the neighbor routers, and a label TLV that specifies one of the neighbor-labels mapped to the FEC for the one of the neighbor routers.

19. The router of claim 11 , wherein, when the router no longer operates as a neighbor to one of the neighbor routers, the routing engine sends a LDP neighbor-label withdraw message to each of the LDP peer routers indicating to not use the previously distributed neighbor-label mapping for the one of the neighbor routers.

20. The router of claim 19 , wherein, in response to sending the LDP neighbor-label withdraw message, the routing engine receives a LDP neighbor-label release message from each of the LDP peer routers indicating that the LDP peer routers do not need the previously distributed neighbor-label mapping for the one of the neighbor routers.

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Assignees

• Juniper Networks Inc

Inventors

• Esale Santosh

Classifications

• H04L45/507 Primary

  Label distribution · CPC title

• H04L45/18

  Loop-free operations · CPC title

• H04L45/22

  Alternate routing · CPC title