CRLSP setup procedure

As shown in Figure 39, a CRLSP is set up by using the following steps:

  1. The ingress LSR generates a Path message that carries LABEL_REQUEST, and then forwards the message along the path calculated by CSPF hop-by-hop towards the egress LSR.

  2. After receiving the Path message, the egress LSR generates a Resv message carrying the reservation information and the LABEL object. It forwards the Resv message to the ingress LSR along the reverse direction of the path that the Path message traveled.

    The Resv message advertises labels, reserves resources, and creates a reserve state on each LSR it passes, so QoS can be guaranteed for services transmitted on the CRLSP.

  3. When the ingress LSR receives the Resv message, the CRLSP is established.

Figure 39: Setting up a CRLSP