RSVP-TE Scalability - Protocol Extension - Conditional PathTear

RSVP Traffic Engineering (TE) protocol extensions to support Refresh-interval Independent RSVP (RI-RSVP) defined RFC 8370 for fast reroute (FRR) facility protection allows for greater scalability of label-switched paths (LSPs), faster convergence times, and decreased RSVP signaling message overhead from periodic refreshes. On Juniper devices, RSVP-TE runs in enhanced FRR mode, also known as RI-RSVP mode, by default, which includes protocol extensions to support RI-RSVP for FRR facility bypass originally specified in RFC 4090. Specifically, this feature introduces the Conditional PathTear message. The Conditional PathTear message is indicated with an M flag in the new optional Conditions object. When a node that is not a Node Protection Merge Point (NP-MP) receives a Conditional PathTear message, the node deletes the LSP state, and processes Conditional PathTear by considering it as a normal PathTear. Specifically, the node does not propagate Conditional PathTear downstream but removes the optional Conditions object and sends the normal PathTear downstream. When a node that is an NP-MP receives Conditional PathTear, it does not delete the LSP state. The node checks whether the Previous Hop (PHOP) node had previously set the "NP available" flag in Path Record Route Object (RRO) flags. If the flag had been set previously by PHOP, then the node clears "local protection available" and "NP available" flags in the PHOP's RRO flags and triggers PathTear downstream. A Conditional PathTear message is treated as a normal PathTear message by nodes without support for RI-RSVP.