H3C Technologies H3C S10500 Series Switches - Manual (Page 60)

49
MPLS network structure
Figure 14 Diagram of the MPLS network structure
LER
Ingress LSR
LSP
LER
Egress LSR
Transit LSR
IP network
IP network
MPLS domain
LSRs in the same routing or administrative domain form an MPLS domain.
An MPLS domain consists of the following types of LSRs:
• 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
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.
1. Establishing a static LSP through manual configuration
To establish a static LSP, you must 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. However,
static LSPs cannot adapt to network topology changes. Therefore, static LSPs are suitable for small-scale
networks with simple, stable topologies.
2. 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 document discusses LDP only. For more information about LDP, see “
LDP .”
NOTE:
In this document, the term label distribution protocols represents all protocols for label distribution, and the
term LDP refers to the Label Distribution Protocol defined in RFC 5036.