G9 bearer topology of one province is as follows:
NE80 and NE40 apply VRP3.10-2222 version. NE40 and NE80 apply POS155M and are connected through transmission link. They enable APDP + interface backup to realize fast convergence. The transmission link scheduling number is disordered. When transmission engineer enables loop for one transmission link on network management, he wrongly operates transmission link of G9 bearer network. The bearer network does not enable fast convergence and the service interrupts instantaneously.
Cancel link loop operation and the network recovers.
APDP (All Path Detection Protocol) is self-developed new feature protocol. It is mainly used to realize rapid discovery of link problem (millisecond/second-level) and then inform other application features to support rapid reflection of other application features. APDP is used with others. At present it supports interface backup (within 50ms it detects interface problem and makes the service switch to backup interface) and 50ms switchover of weak policy (If outbound interface of weak policy is problematic, it can detect problem within 50ms and make the service switch to normal route interface).
However, there is one problem for transmission loop: when the transmission creates loop as shown in the figure above, transmission link loops NE80-1 between NE80-1 and NE40-1. On NE40-1 APDP will detect link problem and make switchover. 但NE80-1 will receive APDP packet sent by itself because of link loop. There is no APDP switchover on NE80-1.
PPP link between two routers is down because the link interrupts. The service interrupts instantaneously because fast convergence is not enabled on bearer network.
BFD function based on VRP5 can solve the problem.