3. MPLS multicast control plane

An MPLS tree can be set up statically, by configuring label matches on all the LSRs in the tree. This is a simple approach, but one that is quickly cumbersome in terms of configuration and, above all, not very reactive to failures or topology changes.

To ensure automatic and dynamic MPLS tree establishment, it is necessary to have a signaling protocol that distributes labels between LSRs along the tree. To support this function, the IETF MPLS working group has chosen to extend the two MPLS unicast signaling protocols: LDP and RSVP-TE. This pragmatic approach allows maximum reuse of existing signaling procedures, speeding up implementation and facilitating interoperability. This approach also avoids the multiplication of protocols in the network, thus facilitating operations. The sections below describe the extensions to LDP and RSVP-TE for MPLS tree establishment,...