R2511-HP MSR Router Series MPLS Configuration Guide(V5)

MPLS network structure

Figure 3 MPLS network structure

LSRs in the same routing or administrative domain form an MPLS domain.

An MPLS domain has the following LSR types:

• Ingress LSRs—Receive and label packets coming into the MPLS domain.

• Transit LSRs—Forward packets along LSPs to their egress LERs according to the labels.

• Egress LSRs—Remove labels from packets and forward the packets to their destination networks.

LSP establishment and label distribution

This section describes how MPLS sets up LSPs and distribute labels.

LSP establishment

Establishing LSPs is to bind FECs with labels on each LSR involved and notify its adjacent LSRs of the

bindings, so as to establish the LFIB on each LSR. LSPs can be manually established through configuration,

or dynamically established through label distribution protocols.

• Establishing a static LSP through manual configuration:

Static LSPs do not dynamically change in response to network topology changes, and are suitable

for small-scale, stable, and simple networks. To establish a static LSP, assign a label to the FEC on

each LSR along the packet forwarding path. Establishment of static LSPs consumes fewer resources

than dynamic LSP establishment.

• Establishing an LSP through a label distribution protocol:

Label distribution protocols are MPLS signaling protocols. They can classify FECs, distribute labels,

and establish and maintain LSPs. Label distribution protocols include protocols designed

specifically for label distribution, such as the Label Distribution Protocol (LDP), and protocols

extended to support label distribution, such as BGP and RSVP-TE.

This chapter discusses LDP only. For more information about LDP, see "LDP."

NOTE:

In this chapter, the term "label distribution protocols" refers to all protocols for label distribution. The term

"LDP" refers to the RFC 5036 LDP.