INS_CWGE24MS2_REV–
10/05/16 PAGE 137
INSTALLATION AND OPERATION MANUAL
CWGE24MS2
TECH SUPPORT: 1.888.678.9427
activates when an ERN receives information about a local switching request, such as after a switch
fail (SF), manual switch (MS), or forced switch (FS). When this timer expires, the ERN begins to
apply actions from the R-APS it receives. This timer cannot be manually stopped.
Wait to restore (WTR) timer -- The RPL owner uses the WTR timer. The WTR timer applies to the
revertive mode to prevent frequent triggering of the protection switching due to port flapping or
intermittent signal failure defects. When this timer expires, the RPL owner sends a R-APS (NR, RB)
through the ring.
Wait to Block (WTB) timers -- This wait-to-block timer is activated 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 the clearing of a single FS command
does not trigger the re-blocking of the RPL. The WTB timer is defined to be 5 seconds longer than
the guard timer, which is enough time to allow a reporting ERN to transmit two R-APS messages
and allow the ring to identify the latent condition. When clearing a MS command, the WTB timer
prevents the formation of a closed loop due to the RPL owner node applying an outdated remote
MS request during the recovery process.
Hold-off timer -- Each ERN uses a hold-off timer to delay reporting a port failure. When the timer
expires, the ERN checks the port status. If the issue still exists, the failure is reported. If the issue
does not exist, nothing is reported.
ERPS revertive and non-revertive switching
ERPS considers revertive and non-revertive operation. In revertive operation, after the condition(s)
causing a switch has cleared, the traffic channel is restored to the working transport entity, i.e.
blocked on the RPL. In the case of clearing of a defect, the traffic channel reverts after the expiry
of a WTR timer, which is used to avoid toggling protection states in case of intermittent defects.
In non-revertive operation, the traffic channel continues to use the RPL, if it is not failed, after a
switch condition has cleared.
Control VLAN:
The pure ERPS control packets domain only, no other packets are transmitted in this vlan to
guarantee no delay for the ERPS. So when you configure a Control VLAN for a ring, the vlan
should be a new one. The ERPS will create this control vlan and its member ports automatically.
The member port should have the Left and Right ports only.
In ERPS, the control packets and data packets are separated in different vlans.
The control packets are transmitted in a vlan which is called the Control VLAN.
Instance:
For ERPS version 2, the instance is a profile specifies a control vlan and a data vlan or multiple
data vlans for the ERPS. In ERPS, it can separate the control packets and data packets in different
vlans. The control packets is in the Control VLAN and the data packets can be in one or multiple
data vlan. And then user can assign an instance to an ERPS ring easily.
