LDP downstream on demand

The Label Distribution Protocol (LDP) is widely deployed in downstream unsolicited advertisement mode. As service providers integrate the access and aggregation networks into a single MPLS domain, LDP downstream on demand is needed to distribute the bindings between access and aggregation networks to keep the access node control plane as lightweight as possible and to avoid storing thousands of label bindings from upstream aggregation nodes. Instead of learning and storing all label bindings for all possible loopback addresses within the MPLS network, the access node uses LDP downstream on demand to request the label bindings for only the FECs corresponding to the loopback addresses of those egress nodes to which it has services configured.