Advice on When It is Safe to Start Sending Data on Label Switched Paths Established Using RSVP-TE
The Resource Reservation Protocol (RSVP) has been extended to support Traffic Engineering (TE) in Multiprotocol Label Switching (MPLS) and Generalized MPLS (GMPLS) networks. The protocol enables signaling exchanges to establish Label Switched Paths (LSPs) that traverse nodes and links to provide end-to-end data paths. Each node is programmed with "cross-connect" information as the signaling messages are processed. The cross-connection information instructs the node how to forward data that it receives. End points of the LSP need to know when it is safe to start sending data so that it is not misdelivered and so that safety issues specific to the data plane technology are satisfied. Likewise, all label switching routers along the path of the LSP need to know when to programme their data planes relative to sending control plane messages. This document clarifies and summarises the RSVP-TE protocol exchanges with relation to the programming of cross-connects along an LSP for both unidireciotnal and bidirecitonal LSPs. This document does not define any new procedures or protocol extensions, and defers completely to the documents that normative references. The clarifications set out in this document may also be used to help interpret LSP establishment performance figures for MPLS-TE and GMPLS devices.