Overview of MPLS LDP

Definition

The Label Distribution Protocol (LDP) is a control protocol of Multiprotocol Label Switching (MPLS) that functions like a signaling protocol on a traditional network. LDP classifies forwarding equivalence classes (FECs), distributes labels, and establishes and maintains label switched paths (LSPs). LDP defines messages used in the label distribution process as well as procedures for processing these messages.

Purpose

MPLS is highly scalable because it allows multiple labels in a packet and has a connection-oriented forwarding plane. This scalability enables an MPLS/IP network to provide a variety of services. Label switching routers (LSRs) on an MPLS network use LDP to map Layer 3 routing information to Layer 2 switched paths, and establish LSPs at the network layer.

LDP is widely used to provide VPN services because of its simple deployment and configuration, abilities to set up LSPs dynamically based on routing information, and support for a large number of LSPs.