Editing Label Distribution Protocol (section)

==LDP==

[[File:LDP session establishment.jpg|right|thumb|LDP session establishment]]
The Label Distribution Protocol (LDP) is a protocol defined by the IETF (RFC 5036) for the purpose 
of distributing labels in an MPLS environment. LDP relies on the underlying routing information provided by an [[Interior gateway protocol|IGP]] in order to forward label packets. The router [[forwarding information base]], or FIB, is responsible for determining the 
hop-by-hop path through the network. 
Unlike traffic-engineered paths, which use constraints and explicit routes to establish end-to-end LSPs, LDP is used only for signaling best-effort LSPs.

===Authentication===

LDP sessions carried over TCP can be authenticated using the ''TCP MD5 Authentication Option''.  While the IETF considers the ''TCP MD5 Authentication Option'' deprecated in favor of the algorithm-independent ''TCP Authentication Option'', in practice the ''TCP MD5 Authentication Option'' is much more widely available in commercial routers as of July 2023.  Use of authenticated LDP-over-TCP helps provide strong integrity protection against misconfigured would-be LDP peers.{{cn|date=July 2023}}