RFC 3210 (rfc3210) - Page 3 of 8
Applicability Statement for Extensions to RSVP for LSP-Tunnels
Alternative Format: Original Text Document
RFC 3210 Applicability Statement for Extensions December 2001 (5) tracking of the actual route traversed by an LSP-tunnel (6) diagnostics on LSP-tunnels (7) the concept of nodal abstraction (8) preemption options that are administratively controllable The RSVP-TE specification introduces several new RSVP objects, including the LABEL-REQUEST object, the RECORD-ROUTE object, the LABEL object, the EXPLICIT-ROUTE object, and new SESSION objects. New error messages are defined to provide notification of exception conditions. All of the new objects defined in RSVP-TE are optional with respect to the RSVP protocol, except the LABEL-REQUEST and LABEL objects, which are both mandatory for the establishment of LSP- tunnels. Two fundamental aspects distinguish the RSVP-TE specification [1] from the original RSVP protocol [3]. The first distinguishing aspect is the fact that the RSVP-TE specification [1] is intended for use by label switching routers (as well as hosts) to establish and maintain LSP-tunnels and to reserve network resources for such LSP-tunnels. The original RSVP specification [3], on the other hand, was intended for use by hosts to request and reserve network resources for micro-flows. The second distinguishing aspect is the fact that the RSVP-TE specification generalizes the concept of "RSVP flow." The RSVP-TE specification essentially allows an RSVP session to consist of an arbitrary aggregation of traffic (based on local policies) between the originating node of an LSP-tunnel and the egress node of the tunnel. To be definite, in the original RSVP protocol [3], a session was defined as a data flow with a particular destination and transport layer protocol. In the RSVP-TE specification, however, a session is implicitly defined as the set of packets that are assigned the same MPLS label value at the originating node of an LSP-tunnel. The assignment of labels to packets can be based on various criteria, and may even encompass all packets (or subsets thereof) between the endpoints of the LSP-tunnel. Because traffic is aggregated, the number of LSP-tunnels (hence the number of RSVP sessions) does not increase proportionally with the number of flows in the network. Therefore, the RSVP-TE specification [1] addresses a major scaling issue with the original RSVP protocol [3], namely the large amount of system resources that would otherwise be required to manage reservations and maintain state for potentially thousands or even millions of RSVP sessions at the micro-flow granularity. The reader is referred to [1] for a technical description of the RSVP-TE protocol specification. Awduche, et. al. Informational
