RSVP-TE-based signaling provides a means to establish tunnels dynamically.
RSVP-TE uses the Downstream on Demand (DOD) label distribution mode, sending PATH messages from the ingress LER node to the egress LER and RESV messages in the reverse direction. DOD label distribution is a router’s response to an explicit request from another router for label binding information. The DOD mode is in contrast to LDP on the 7705 SAR, which uses the Downstream Unsolicited (DU) label distribution mode for both PWs and LSPs. A router in DU mode will distribute label bindings to another router that has not explicitly requested the label bindings.
RSVP-TE signaling is supported when the 7705 SAR is deployed as an LER and as an LSR. When used as an LER, the 7705 SAR uses RSVP-TE signaling to set up constrained paths because only the LER knows all the constraints imposed on the LSP. When used as an LSR, the 7705 SAR uses RSVP-TE to interpret the RSVP-TE messages (including all the constraints).
With RSVP-TE, users can choose which services and PWs may use a particular LSP. One-to-one or many-to-one scenarios for binding PWs to RSVP-TE LSPs is supported, which is similar to binding PWs to static LSPs. Furthermore, each RSVP-TE LSP can be configured with its own set of attributes and constraints.