Table 35: Erps Request/State Priority - Edge-Core ECS4660-28F Management Manual

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nodes where further forced switch commands are issued

block the traffic channel and R-APS channel on the ring port

at which the forced switch was issued. The ring node where

the forced switch command was issued transmits an R-APS

message over both ring ports indicating FS. R-APS (FS)

messages are continuously transmitted by this ring node

while the local FS command is the ring node's highest

priority command. As such, two or more forced switches are

allowed in the ring, which may inadvertently cause the

segmentation of an ring. It is the responsibility of the

operator to prevent this effect if it is undesirable.

Ring protection requests, commands and R-APS signals have

the priorities as specified in the following table.

Table 35: ERPS Request/State Priority

Request / State and Status

local clear SF

R-APS (NR, RB)

* If an Ethernet Ring Node is in the Forced Switch state, local SF is

Recovery for forced switching under revertive and non-

revertive mode is described under the Revertive parameter.

When a ring is under an FS condition, and the node at which

an FS command was issued is removed or fails, the ring

remains in FS state because the FS command can only be

cleared at node where the FS command was issued. This

results in an unrecoverable FS condition.

When performing a maintenance procedure (e.g., replacing,

upgrading) on a ring node (or a ring link), it is recommended

that FS commands be issued at the two adjacent ring nodes

instead of directly issuing a FS command at the ring node

| Basic Administration Protocols

Ethernet Ring Protection Switching

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