MPLS intro from cicso

Topics: Routing, Router, Multiprotocol Label Switching Pages: 141 (23391 words) Published: December 3, 2013
Multiprotocol Label Switching Overview
This chapter describes the Multiprotocol Label Switching (MPLS) distribution protocol. MPLS is a high-performance packet forwarding technology that integrates the performance and traffic management capabilities of data link layer (Layer 2) switching with the scalability, flexibility, and performance of network-layer (Layer 3) routing. It enables service providers to meet challenges brought about by explosive growth and provides the opportunity for differentiated services without necessitating the sacrifice of existing infrastructure.

The MPLS architecture is remarkable for its flexibility:

Data can be transferred over any combination of Layer 2 technologies

Support is offered for all Layer 3 protocols

Scaling is possible well beyond anything offered in today’s networks.

Specifically, MPLS can efficiently enable the delivery of IP services over an ATM switched network. It supports the creation of different routes between a source and a destination on a purely router-based Internet backbone. Service providers who use MPLS can save money and increase revenue and productivity.

Procedures for configuring MPLS are provided in the “Configuring Multiprotocol Label Switching” chapter later in this publication.


Label switching on a router requires that Cisco Express Forwarding (CEF) be enabled on that router. Refer to the CEF feature documentation for configuration information. For more information on enabling CEF, see the “Configuring Cisco Express Forwarding” chapter in this publication. This chapter describes MPLS. It contains the following sections: •

MPLS/Tag Switching Terminology

MPLS Commands and Saved Configurations

MPLS/Tag Switching CLI Command Summary


Label Switching Functions

Distribution of Label Bindings

MPLS and Routing

MPLS Traffic Engineering

MPLS Virtual Private Networks

Cisco IOS Switching Services Configuration Guide


Multiprotocol Label Switching Overview
MPLS/Tag Switching Terminology

MPLS Quality of Service

MPLS Label Switch Controller

MPLS Egress NetFlow Accounting

MPLS/Tag Switching Terminology
Beginning with Cisco IOS Release 12.1, the Tag Switching distribution protocol has been replaced with the MPLS distribution protocol. MPLS supports the following: •

Tag Switching features

Tag Switching command-line interface (CLI) commands

Table 19 lists tag switching terms (found in earlier releases of this document) and the equivalent MPLS terms used in this document.
Table 19

Equivalency Table for Tag Switching and MPLS Terms

Old Tag Switching Terminology

New MPLS Terminology

Tag Switching

Multiprotocol Label Switching (MPLS)

Tag (short for Tag Switching)


Tag (item or packet)


TDP (Tag Distribution Protocol)

LDP (Label Distribution Protocol)
Cisco TDP and LDP (MPLS Label Distribution Protocol) are
nearly identical in function, but use incompatible message
formats and some different procedures. Cisco is changing
from TDP to a fully compliant LDP.

Tag Switched

Label Switched

TFIB (Tag Forwarding Information

LFIB (Label Forwarding Information Base)

TSR (Tag Switching Router)

LSR (Label Switching Router)

TSC (Tag Switch Controller)

LSC (Label Switch Controller)

ATM-TSR (ATM Tag Switch Router)

ATM-LSR (ATM Label Switch Router, such as the
Cisco BPX 8650 switch)

TVC (Tag VC, Tag Virtual Circuit)

LVC (Label VC, Label Virtual Circuit)

TSP (Tag Switch Path)

LSP (Label Switch Path)

XTag ATM (extended Tag ATM port)

XmplsATM (extended MPLS ATM port)

MPLS Commands and Saved Configurations
During the transition period from tag switching to MPLS, if a configuration command has both MPLS and tag switching forms, the tag switching version is written to saved configurations. For example, you can configure MPLS...
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