Mpls Overview; Chapter 1 Mpls Architecture; Mpls Basic Concepts - 3Com 3C13636 Configuration Manual

3Com Router 3000 Ethernet Family
Configuration Guide

Chapter 1 MPLS Architecture

1.1 MPLS Overview

MPLS (Multiprotocol Label Switching) encapsulates packets with labels of short and
fixed length. MPLS obtains service from various link layers (such as PPP, ATM, Frame
Relay, and Ethernet) and provides connection-oriented service for network layer. MPLS
can obtain support from IP routing protocol and control protocol and, at the same time,
it supports policy-based restraint route. It possesses powerful and flexible routing
functions and is capable of satisfying the requirements for the network from various
new applications. This technology was initially originated from IPV4. However, its core
technology can be extended to multiple network protocols (IPV6, IPX, etc).
MPLS is a protocol initially developed for increasing forwarding speed of routers.
However, it has gained wider applications in traffic engineering, VPN, and QoS and is
becoming an important standard for large-scale IP networks.

1.2 MPLS Basic Concepts

1.2.1 FEC
Forwarding Equivalent Class (FEC), in fact, is a kind of classify-and-forward technology.
It categorizes packets with the same forwarding strategy (same destination addresses,
same forwarding routes and same QoS levels) into one group, which is called a FEC.
The FEC classification is based on the network layer address. Packets in the same
FEC will be processed in absolutely the same way.
1.2.2 Label
I. Label definition
Label is a locally significant and short identifier with fixed length, which is used to
identify a particular FEC. When reaching at MPLS network ingress, packets are divided
into different FECs, on which different labels are encapsulated. Later forwarding is
based on these labels.
II. Label structure
The structure of the label is shown in Figure 1-1.
Label
Figure 1-1 Label structure
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Chapter 1 MPLS Architecture