 Labels are distributed between LERs and LSRs using the Label Distribution Protocol (LDP).LSRs in an MPLS network regularly exchange label and reachability information with each other using standardized procedures in order to build a complete picture of the network so they can then use to forward packets.Label-switched paths (LSPs) are established by the network operator for a variety of purposes, such as to create network-based IP virtual private networks or to route traffic along specified paths through the network.