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Pseudowire Switching

Page 142 7210 SAS M Services Guide

Pseudowire Switching with Protection

Pseudowire switching scales VLL and VPLS services over a multi-area network by removing the

need for a full mesh of targeted LDP sessions between PE nodes. Figure 22 illustrates the use of

pseudowire redundancy to provide a scalable and resilient VLL service across multiple IGP areas

in a provider network.

Figure 22: VLL Resilience with Pseudowire Redundancy and Switching

In the network in Figure 22, PE nodes act as masters and pseudowire switching nodes act as slaves

for the purpose of pseudowire signaling. A switching node will need to pass the SAP Interface

Parameters of each PE to the other.T-PE1 sends a label mapping message for the Layer 2 FEC to

the peer pseudowire switching node” for example, S-PE1. It will include the SAP interface

parameters, such as MTU, in the label mapping message. S-PE1 checks the FEC against the local

information and if a match exists, it appends the optional pseudowire switching point TLV to the

FEC TLV in which it records its system address. T-PE1 then relays the label mapping message to

S-PE2. S-PE2 performs similar operations and forwards a label mapping message to T-PE2. The

same procedures are followed for the label mapping message in the reverse direction, for example,

OSSG114-7210M

Core area

Metro area B

Metro area A

Access Node

7750 T-PE2

7750 T-PE1

7210

7210 S-PE3

7210 S-PE1

7750 T-PE3

Primary PW

Standby PW

7210

7210 S-PE4

PW switching

SDP6:600

SDP4:400

SDP1:100

SDP3:300

7210 S-PE2

PW switching

Alcatel-Lucent 7210 SAS M Service Guide

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