One DSLAM dual-homes to two NE40Es. Two NE40Es only has POS L3 link and no L2 link. Interface attribute of NE40E is subInterface. Multicast routing protocol of NE40E is PIM-SM and IGMP. When IPTV service is operated, downlink traffic of IPTV only passes one link (master link). Another link is backup link. When master link is problematic, the service auto switches over backup link. It is switchover time. When master link recovers, the service returns. It is revertback time. These two indexes are test items of IPTV deployment.
NE40E version: NE40E-VRP5.30-31002A.3101. When testing on the spot, set hello timer=1, hold timer=4; query timer=4, max-response-timer=2, the unit is second. Test result (at least 20 times of test): switchover time is about 4s on average and revertback time is about 2s on average. Users recognize the result.
Switchover time and revertback time are related with four timers: hello timer and hold timer of PIM-SM; query timer and max-response-timer of IGMP. Switchover is related with hold timer and revertback time is related with max-response-timer. If these four timers are not set, it will influence switchover time and revertback time. It has effect on the recovery of IPTV service.
Note: RFC2362(PIM-SM) suggests hold timer=3.5*hello timer. RFC2236(IGMP V2) suggests that query timer is larger than max-response-timer.
The command of four timers of NE40E is as follows:
timer query 4
timer hello 1
hello-option holdtime 4