Figure 57: MPLS Interface Stacking for the Interface Label Space
Related Topics MPLS Label Switching and Packet Forwarding on page 209â–
â– MPLS Label Distribution Methodology on page 218
â– MPLS Label Distribution Protocols on page 229
MPLS Label Distribution Protocols
Label distribution protocols create and maintain the label-to-FEC bindings along an
LSP from MPLS domain ingress to MPLS domain egress. A label distribution protocol
is a set of procedures by which one LSR informs a peer LSR of the meaning of the
labels used to forward traffic between them. It enables each peer to learn about the
other peer’s label mappings. The label distribution protocol provides the information
MPLS uses to create the forwarding tables in each LSR in the MPLS domain.
NOTE: Label distribution protocols are sometimes referred to as signaling protocols.
However, label distribution is a more accurate description of their function and is
preferred in this text.
The following protocols are currently used for label distribution:
■BGP—Border Gateway Protocol
■LDP—Label Distribution Protocol
■RSVP-TE—Resource Reservation Protocol with traffic-engineering extensions
that enable label binding and explicit route capability
NOTE: To reduce confusion, this text uses the lowercase term, label distribution
protocol, to refer to the generic class of protocols. The acronym, LDP, refers only to
the particular protocol named Label Distribution Protocol.
BGP and LDP have no traffic-engineering capability and support only best-effort LSPs.
LDP supports topology-driven MPLS networks in best-effort, hop-by-hop
implementations. RSVP-TE is used primarily for MPLS applications that require traffic
MPLS Label Distribution Protocols â– 229
Chapter 2: MPLS Overview
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