MPLS and RSVP
7450 ESS MPLS Guide Page 79
Figure 22: Failed Condition - Switching at Z
The unidirectional PSC protocol initiates protection switching: the selector bridge at node A is
switched to protection connection A-to-Z and the selector at node A switches to protection
connection Z to-A. The PSC packet, sent from node A to node Z, requests a protection switch to
node Z.
After node Z validates the priority of the protection switch request, the selector at node Z is
switched to protection connection A-to-Z and the selector bridge at the node Z is switched to
protection connection Z-to-A. The PSC packet, sent from node Z to node A, is used as
acknowledge, informing node A about the switching.
If BFD CC or CC/CV OAM packets are used to detect defects on the working and protection path,
they are inserted on both working and protection paths. It should be noted that they are sent
regardless of whether the selected as the currently active path.
The 7750 supports the following operator commands:
• Forced Switch
• Manual Switch
• Clear,
• Lockout of protection
Switching Static MPLS-TP PWs to Dynamic, T-LDP Signaled PWs
al_0236
A
Working
Selector
Bridge
Selector
Protection
12
21
APS-2
Z
Working
Selector
Bridge
Selector
Protection
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