RSVP make-before-break label reuse

A router comprising:

• a routing engine comprising one or more processors configured to:
• receive, from an upstream router of a label switched path (LSP) established between an 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,
• receive, from a next hop router along the second path of the second LSP instance, a second message including a second downstream label used to identify outgoing traffic associated with the second LSP instance,
• in response to receipt of the second message, determine to reuse a label previously allocated by the router for the first LSP instance to identify incoming traffic associated with the second LSP instance, wherein, to determine to reuse the label, the routing engine configured to determine that the second downstream label is the same as a first downstream label previously received by the router from the same next hop router for the first LSP instance, and
• send a third message including the label for the second LSP instance to the upstream router along the second path of the second LSP instance, wherein the label is the same for the first LSP instance and the second LSP instance;
• and
• a 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 label from the upstream router along the second path of the second LSP instance.

A non-transitory computer-readable medium comprising instructions that when executed cause one or more programmable processors of a router to:

• receive, by the router from an upstream router of a label switched path (LSP) established between an 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;
• receive, by the router from a next hop router along the second path of the second LSP instance, a second message including a second downstream label used to identify outgoing traffic associated with the second LSP instance;
• in response to receiving the second message, determine, by the router, to reuse a label previously allocated by the router for the first LSP instance to identify incoming traffic associated with the second LSP instance, wherein, to determine to reuse the label, the instructions cause the one or more programmable processors to determine, by the router, that the second downstream label is the same as a first downstream label previously received by the router from the same next hop router for the first LSP instance;
• send, by the router to the upstream router along the second path of the second LSP instance, a third message including the label for the second LSP instance, wherein the label is the same for the first LSP instance and the second LSP instance;
• and
• upon establishment of the second LSP instance and tear down of the first LSP instance by the ingress router, receive, by the router from the upstream router along the second path of the second LSP instance, incoming traffic including the label.