Bidirectional MPLS TE tunnel

MPLS Transport Profile (MPLS-TP) uses bidirectional MPLS TE tunnels to implement 1:1 and 1+1 protection switching, and to support in-band detection tools and signaling protocols such as OAM and PSC.

A bidirectional MPLS TE tunnel includes a pair of CRLSPs in opposite directions. It can be established in the following modes:

• Co-routed mode—Uses the extended RSVP-TE protocol to establish a bidirectional MPLS TE tunnel. RSVP-TE uses a Path message to advertise the labels assigned by the upstream LSR to the downstream LSR. RSVP-TE uses a Resv message to advertise the labels assigned by the downstream LSR to the upstream LSR. During the delivery of the path message, a CRLSP in one direction is established. During the delivery of the Resv message, a CRLSP in the other direction is established. The CRLSPs of a bidirectional MPLS TE tunnel established in co-routed mode use the same path.

• Associated mode—In this mode, you establish a bidirectional MPLS TE tunnel by binding two unidirectional CRLSPs in opposite directions. The two CRLSPs can be established in different modes and use different paths. For example, one CRLSP is established statically and the other CRLSP is established dynamically by RSVP-TE.

For more information about establishing MPLS TE tunnel through RSVP-TE, the Path message, and the Resv message, see "Configuring RSVP."