Transition Networks
S4224 Web User Guide
33558 Rev. C
Page 256 of 669
Ring Protection and MEP Configuration
The S4224 lets you configure the RPL port so it can act in the role of Owner or Neighbor on that ring
instance. The WTR time and Hold off timer serve the same purpose as EPS. The Guard timer on the
EPRS instance is configurable and helps in ignoring aged R-APS messages that circulate around the
ring. The Ring ports have the Y.1731 MEPs which exchange CCMs to monitor the health of the link and
also trigger signal failures that can cause the link failure and protection to activate.
The screen above shows a MEP configured with R-APS as the APS Protocol Type. See the “
section on page
Ring Protection Conditions and Commands
The S4224 supports the Ethernet ring
SF
and
NR
conditions per Rec. ITU-T G.8032/Y.1344 (03/2010).
Signal fail (SF)
- When an SF condition is detected on a ring link, and it is determined to be a
"stable" failure, Ethernet ring nodes adjacent to the failed ring link initiate the protection switching
mechanism described in the ITU Recommendation.
No request (NR)
- The condition when no local protection switching requests are active.
The
FS
,
MS
, and
Clear
administrative commands are supported:
Forced switch (FS)
- This command forces a block on the ring port where the command is issued.
Manual switch (MS)
- In the absence of a failure or FS, this command forces a block on the ring
port where the command is issued.
Clear
- The Clear command is used for these operations:
a) Clearing an active local administrative command (e.g., Forced switch or Manual switch).
b) Triggering reversion before the WTR or WTB timer expires in case of revertive operation.
c) Triggering reversion in case of non-revertive operation.
Note that at the time of this publication, other commands (Lockout of protection, Replace the RPL,
Exercise signal) are undergoing further ITU-T study.
