Mpls Network Structure; Lsp Establishment; Figure 7 Mpls Network Structure - Zte ZXR10 8900 Series User Manual

F 7 MPLS N
IGURE ETWORK
egress LSR removes the labels and forwards the packets to the
destinations.
Opposed to conventional IP forwarding, in MPLS, the assignment
of a particular packet to a particular FEC is done just once. It is
done when the packet enters MPLS domain.

MPLS Network Structure

The structure of MPLS network is shown in
S
TRUCTURE
Label Edge Router (LER) is at the edge of a MPLS domain. LSR
assigns labels for packets entering MPLS domain. It implements
functions such as traffic classification, label mapping and label re-
moving, Label Switch Path (LSP) initiation, IP packets forwarding
and Diff-Serv.
Label Switch Router (LSR) is the core router in a MPLS domain. It
supports label switching and label distribution functions. It partic-
ipates in establishing LSP and initiates next-hop change.
Routers in MPLS domain run Label Distribution Protocol (LDP) to
distribute labels for packets.

LSP Establishment

A LSP is a forwarding path established according to MPLS. It is
composed of LSRs and links from source LSR to destination LSR,
which is similar to virtual circuit of ATM.
There are three drive modes to establish a LSP:
�
Packet-based
The packet traffic reaching a LSR springs label distribution. In
this mode, the cost for label distribution is direct proportion to
the traffic. Time delay exists for label distribution.
� Topology-based
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Chapter 2 MPLS Configuration
Figure 7.
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