Cisco ASR 900 Series User Manual

states that the switching must revert to the working LSP immediately. However, the emulated APS
implementation starts a WTR timer and switches after the timer has expired.
An endpoint implementing the newer PSC version may have to communicate with another endpoint
implementing an older version. Because there is no mechanism to exchange the capabilities, the PSC
implementation must interoperate with another peer endpoint implementing emulated APS. In this scenario,
the new implementation sends both the LDI extension message (referred to as emLockout) as well as a PSC
message when the lockout is issued.
Mapping and Priority of emlockout
There are two possible setups for interoperability:
•
New-old implementation.
•
New-new implementation.
You can understand the mapping and priority when an emLockout is received and processed in the new-old
implementation by referring to the following figure.
When the new label edge router (new-LER) receives an emLockout (or emLockout_clear) message, the
new-LER maps the message into an internal local FS’/FSc’ (local FS-prime/FS-prime-clear) or LoP’/LoPc’
(local LoP-prime/Lop-prime-clear) event based on the channel on which it is received. This event is prioritized
by the local event processor against any persistent local operator command. The highest priority event drives
the PSC FSM logic and any associated path protection logic. A new internal state is defined for FS’/FSc’
events. The PSC FSM logic transmits the corresponding PSC message. This message is dropped/ignored by
the old-LER.
In the new-new LER implementation shown in the following figure, each endpoint generates two messages
when a lockout command is given on a working or protected LSP.
MPLS Basic Configuration Guide, Cisco IOS XE Everest 16.5.1 (Cisco ASR 900 Series)
16
MPLS Transport Profile
MPLS-TP Linear Protection with PSC Support

Cisco ASR 900 Series Specifications

General

Brand	Cisco
Model	ASR 900 Series
Category	Network Router
Language	English