82
Enhanced Features
WAGO-ETHERNET-Zubehör 852
852-1305 8/4-Port 100BASE-T/1000BASE-SX/LX
Manual
1.1.0
Guard Timer
All ring subscribers use a “Guard Timer”. It prevents the possibility of forming a
closed loop and prevents ring subscribers from using outdated R-APS messages.
The “Guard Timer” is enabled if a ring subscriber received information on a local
switching request, such as after SF (“
S
witch
F
ail”), MS (“
M
anual
S
witch”) or FS
(“
F
orced
S
witch”) commands. When the timer expires, the ring subscriber begins
executing actions it received from the R-APS. This timer cannot be manually
stopped.
WTR Timer
The “WTR Timer” (“
W
ait
T
o
R
estore
Timer
”) is used by the “RPL Owner”. The
“WTR Timer” applies to the reset mode to prevent frequent triggering of the
protection switching due to port flapping or intermittent signal failure defects.
When the timer expires, the “RPL Owner” sends an R-APS (NR, RB) message
through the ring.
WTB Timer
The “WTB Timer” (“
W
ait
T
o
B
lock
Timer
”) is enabled on the “RPL Owner”.
The “RPL Owner” uses “WTB Timers” before initiating an RPL block and then
reverting to the idle state after operator-initiated commands, such as for FS or MS
conditions, are entered. Because multiple FS commands are allowed to co-exist in
a ring, the “WTB Timer” ensures that clearing a single FS command does not
trigger the re-blocking of the RPL. The “WTB Timer” should be 5 seconds longer
than the “Guard Timer”, enough time to allow a reporting ring subscriber to
receive two R-APS messages and to allow the ring to identify the latent state.
When clearing a MS command, the “WTB Timer” prevents the formation of a
closed loop because the “RPL Owner” node does not respond to an outdated
remote MS request during the recovery process.
Hold-off Timer
Each ring subscriber uses a “Hold-off Timer” to delay reporting a port failure.
When the timer expires, the ring subscriber checks the port status. If the problem
persists, a failure is reported. If the issue does not persist, nothing is reported.
ERPS revertive and non-revertive
switching
ERPS uses revertive and non-revertive operation. In revertive operation after the
conditions causing a switch have cleared, the traffic channel is restored to the
working transport entity, i.e., blocked on the RPL. Once an error condition is
cleared, the traffic channel is switched back only after expiration of a “WTR
Timer” to prevent protecting states from toggling due to intermittent errors.
without revertive operation, the traffic channel continues to use RPL after a
switch condition is cleared if the RPL has not failed.
