RSVP make-before-break label reuse

Patent metadata

Field	Value
Publication number	US-9843508-B2
Application number	US-201514682799-A
Country	US
Kind code	B2
Filing date	Apr 9, 2015
Priority date	Mar 6, 2015
Publication date	Dec 12, 2017
Grant date	Dec 12, 2017

Abstract

Techniques are described for reusing downstream-assigned labels when establishing a new instance of a label switched path (LSP) prior to tearing down an existing instance of the LSP using make-before-break (MBB) procedures for RSVP. The techniques enable a routing engine of any non-ingress router along a path of the new LSP instance to reuse a previously allocated label for the existing LSP instance as the downstream assigned label for the new LSP instance when the paths of the existing LSP instance and the new LSP instance overlap. In this way, the non-ingress router does not need to update a label route in its forwarding plane for the reused label. When the new LSP instance completely overlaps the existing LSP instance, an ingress router of the LSP may avoid updating an ingress route in its forwarding plane for applications that use the LSP.

First claim

What is claimed is:

1. A method comprising:
receiving, by a router from an ingress router of a label switched path (LSP) established between the ingress router and an egress router, a first message requesting establishment of a second LSP instance of the LSP, the second LSP instance having a second path that at least partially overlaps a first path of a first LSP instance of the LSP;
determining, by the router, whether to reuse a first label previously allocated by the router for the first LSP instance as a second label used to identify incoming traffic associated with the second LSP instance;
responsive to determining to reuse the first label as the second label, reusing, by the router, a label route installed in a forwarding plane of the router for the first LSP instance to forward incoming traffic including the second label for the second LSP instance without updating the label route;
sending, by the router to an upstream router along the second path of the second LSP instance, a second message including the second label for the second LSP instance, wherein, responsive to determining to reuse the first label, the second label included in the second message is the same as the first label previously allocated by the router; and
upon establishment of the second LSP instance and tear down of the first LSP instance by the ingress router, receiving, by the router from the upstream router along the second path of the second LSP instance, incoming traffic including the second label.

2. The method of claim 1 , wherein the router comprises the egress router of the LSP, and wherein determining whether to reuse the first label as the second label comprises reusing, by the egress router, the first label previously allocated by the egress router for the first LSP instance as the second label to identify the incoming traffic associated with the second LSP instance without updating a forwarding plane of the egress router.

3. The method of claim 1 , wherein the router comprises a transit router along the second path of the second LSP instance between the ingress router and the egress router of the LSP, and wherein determining whether to reuse the first label as the second label comprises:
receiving, by the transit router from a next hop router along the second path of the second LSP instance, a third message including a second downstream label used to identify outgoing traffic associated with the second LSP instance;
if the second downstream label is the same as a first downstream label previously received by the transit router from the same next hop router for the first LSP instance, reusing, by the transit router, the first label previously allocated by the transit router for the first LSP instance as the second label to identify the incoming traffic associated with the second LSP instance without updating a forwarding plane of the transit router; and
if the second downstream label is different than the first downstream label or the next hop router for the second LSP instance is different than a next hop router for the first LSP instance, allocating, by the transit router, a new label as the second label used to identify the incoming traffic associated with the second LSP instance, and updating the forwarding plane of the transit router.

4. The method of claim 1 , wherein the first message received from the ingress router requesting establishment of the second LSP instance indicates the second path of the second LSP instance between the ingress router and the egress router of the LSP, and wherein the second path is selected by the ingress router based on an amount of overlap with the first path of the first LSP instance.

5. The method of claim 1 , wherein the LSP is protected by a bypass LSP established by the router as a first backup instance for the first LSP instance, the method further comprising:
if the bypass LSP satisfies admission control requirements of the second LSP instance, reusing the bypass LSP as a second backup instance for the second LSP instance without updating a forwarding plane of the router; and
if the bypass LSP does not satisfy the admission control requirements of the second LSP instance, establishing a second backup instance of the bypass LSP for the second LSP instance that satisfies the admission control requirements of the second LSP instance, wherein the second backup instance overlaps the first backup instance, and reuses labels previously allocated for the first backup instance without updating the forwarding engine of the router.

6. The method of claim 1 , wherein the LSP is protected by a first detour LSP established by the router for the first LSP instance, the method further comprising establishing a second detour LSP for the second LSP instance that satisfies admission control requirements for the second LSP instance, wherein a path of the second detour LSP overlaps a path of the first detour LSP and reuses labels previously allocated for the first detour LSP without updating a forwarding plane of the router.

7. A router comprising:
a routing engine comprising one or more processors configured to:
receive, from an ingress router of a label switched path (LSP) established between the ingress router and an egress router, a first message requesting establishment of a second LSP instance of the LSP, the second LSP instance having a second path that at least partially overlaps a first path of a first LSP instance of the LSP,
determine whether to reuse a first label previously allocated by the router for the first LSP instance as a second label used to identify incoming traffic associated with the second LSP instance,
responsive to determining to reuse the first label as the second label, reuse a label route installed in a forwarding engine of the router for the first LSP instance to forward incoming traffic including the second label for the second LSP instance without updating the label route, and
send a second message including the second label for the second LSP instance to an upstream router along the second path of the second LSP instance, wherein, responsive to determining to reuse the first label, the second label included in the second message is the same as the first label previously allocated by the router; and

the forwarding engine comprising one or more processors configured to, upon establishment of the second LSP instance and tear down of the first LSP instance by the ingress router, receive incoming traffic including the second label from the upstream router along the second path of the second LSP instance.

8. The router of claim 7 , wherein the router comprises the egress router of the LSP, and wherein the routing engine is configured to reuse the first label previously allocated by the egress router for the first LSP instance as the second label to identify the incoming traffic associated with the second LSP instance without updating the forwarding engine of the egress router.

9. The router of claim 7 , wherein the router comprises a transit router along the second path of the second LSP instance between the ingress router and the egress router of the LSP, and wherein the routing engine is configured to:
receive, from a next hop router along the second path of the second LSP instance, a third message including a second downstream label used to identify outgoing traffic associated with the second LSP instance;
if the second downstream label is the same as a first downstream label previously received by the transit router from the same next hop router for the first LSP instance, reuse the first label previously allocated by the transit router for the first LSP instance as the second label to identify the incoming traffic associated with the second LSP instance without updating the forwarding engi

Assignees

• Juniper Networks Inc

Inventors

• Dai Minjie
• Shen Yimin
• Torvi Raveendra
• Jork Markus
• Rekhter Yakov
• Venkataraman Natrajan

Classifications

• H04L45/507 Primary

  Label distribution · CPC title

• H04L45/128 Primary

  for finding disjoint paths · CPC title

• H04L45/50

  using label swapping, e.g. multi-protocol label switch [MPLS] · CPC title