Figure 31: Pseudowire Switching Network - Alcatel-Lucent 7705 Service Manual

T-PE1 then relays the label mapping message to S-PE2. S-PE2 performs a similar operation
and forwards a label mapping message to T-PE2.
7705 SAR
T-PE2
Access
Node
Primary PW
Standby PW
The same procedures are followed for the label mapping message in the reverse direction;
for example, from T-PE2 to T-PE1. S-PE1 and S-PE2 will affect the spoke SDP
cross-connect only when both directions of the pseudowire have been signaled and matched.
Pseudowire status notification messages can be generated by the T-PE nodes and/or the
S-PE nodes. Pseudowire status notification messages received by a switching node are
processed and then passed on to the next hop. An S-PE node appends the optional
pseudowire switching TLV, with its system address added to it, to the FEC in the
pseudowire status notification message only if it originated the message or the message was
received with the TLV in it. If the S-PE node is not the originator or if there is no TLV with
the system address in the message, this means that the message was originated by a T-PE
node. In this case, the S-PE processes and passes the message without changes except for the
VC ID value in the FEC TLV.
The merging of the received TLDP status notification message and the local status for the
spoke SDPs from the service manager at a 7705 SAR PE complies with the following rules.
7705 SAR OS Services Guide

Figure 31: Pseudowire Switching Network

switching
SDP
3:300
7705 SAR
7705 SAR
Metro
area B
7x50 7x50
T-PE3
SDP
6:600
switching
• When the local status for both spokes is up, the S-PE passes any received SAP or
SDP-binding generated status notification message unchanged. For example, the
status notification TLV is unchanged but the VC-ID in the FEC TLV is set to the
value of the pseudowire segment to the next hop.
PW PW
switching
SDP
1:100
7705 SAR
S-PE3 S-PE1
SDP
Core
4:400
area
7x50 7x50
T-PE4 T-PE2
PW PW
switching
7705 SAR
T-PE1
7705 SAR
Metro
area B
7x50 7x50
VLL Services
Access
Node
20905
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