T-MPLS 1:1 Linear tunnel protection

Automatic protection switching

Automatic protection switching (APS) is used to control protection switching operations. APS carries information about the protection architecture, the remote node condition, the signal that the near end requests to be carried over the protection path and the signal that is bridged onto the protection path.

Switch initiation criteria

The APS switch initiation criteria are:

• Externally initiated commands, by operator:

  • Clear

  • Lockout of Protection (LO)

  • Forced Switch (FS)

  • Manual Switch (MS)

• Automatically initiated command associated with a protection domain: Signal Fail (SF)

• States of the protection switching function:

  • Wait to Restore (WTR)

  • No Request (NR)

Switching priority

The priority order is according to the Request/State field of the APS payload structure, that is, considering a decreasing priority from top to the bottom in the following list:

• Lockout of Protection (LO)

• Signal Fail for Protection (SF-P)

• Forced Switch for Working (FS)

• Signal Fail for Working (SF)

• Manual Switch for Working / Manual Switch for Protection (MS)

• Wait to Restore (WTR)

• No Request (NR)