Label Distribution Protocol

Standardized in RFC 3036, “LDP Specification,” LDP exchanges labels for IGP and static routes. As mentioned earlier, Cisco's implementation of MPLS traffic engineering is not based on CR-LDP, which is an extension of LDP protocol for constrained based routing. However, understanding LDP is useful even in an MPLS TE network; often, MPLS-enabled networks run a mix of LDP and RSVP in different places.

Because this book is not really about LDP, and because RFC 3036 is more than 130 pages long, an exhaustive discussion of LDP is out of the scope of this chapter (and book). However, the following sections present enough details for you to understand the basics of LDP, as well as some of the packet format details. When you ...

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