OmniSwitch OS6860/OS6900/OS10K Troubleshooting Guide Part No.032996-00 Rev.A
AOS Release 7.X and 8.X January 2015
Alcatel-Lucent Page 134 of 148
in the blocking state to avoid any loop. The node then flushes the FDB for both the ring ports and goes to the
PROTECTION state. All other nodes receiving the R-APS (SF) PDU unblock their blocked port (RPL port at
RPL node) and then go to the PROTECTION state and flush the FDB for their ring ports. If the node whose
ring port goes down is RPL node then there will be no drop in the traffic and if the node is non ERP node then
the traffic is switched through the protection path.
Similarly, if any node goes down then the nodes connected to that node detects the EVENT "local SF". If the
node that goes down is non RPL, then the RPL port goes to the forwarding state on reception of R-APS (SF)
PDU and then traffic is switched through it. And if RPL node goes down, then all the other nodes go to the
PROTECTION state but there will be no drop in the traffic.
If the down ring port comes up for a node in PROTECTION state, then that node detects the EVENT "local
Clear SF". The node starts the guard timer and then transmits R-APS (NR) if the node is non RPL or transmits
R-APS (NR, RB) if the node is RPL. While the guard timer is running, the node will not process any in-
coming R-APS PDU which allows us to ignore the out-dated R-APS PDUS that might be flowing in the
network. If the ring node receiving R-APS (NR) message is having its ring ports block, then it compares the
remote node ID information with its own node ID. If the remote node ID is higher than its own node ID then
unblock its ring ports.
On reception of R-APS (NR) by RPL node and if the revertive mode is enabled, it will trigger the WTR timer
and all the ERP nodes then go to the PENDING state. After the WTR expiry it blocks its RPL port and
unblocks its non RPL port. It then transmits R-APS (NR, RB) PDU and flushes the FDB for ring ports. All the
ERP nodes then go to the IDLE state. On reception of R-APS (NR, RB) by non RPL nodes, they unblock their
ring ports and stop transmitting the R-APS PDU. They also flush the FDB for their ring ports.
Additional Commands
Below is the command to view the statistics for a particular ring:
-> show erp statistics ring <ringId>
Below is an example:
-> show erp statistics ring 1
Legends: R-APS - Ring Automatic Protection Switching
RPL - Ring Protection Link
Ring-Id : 1
Ring Port : 1/1/1
Signal Fail PDUs
Sent : 12,
Recv : 9,
Drop : 0
No Request PDUs
Sent : 4,
Recv : 54,
Drop : 0
No Request RPL Block PDUs
Sent : 3,
Recv : 1170,
Drop : 0
Invalid R-APS PDUs
Recv : 0
Ring Port : 1/1/2
Signal Fail PDUs
Sent : 0,
Recv : 0,
Drop : 0
No Request PDUs
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