PS drop call caused by GTPU failure【Phenomenon Description】In G country C project, We are reported that there

are some GTPU Failure caused call drop recently, but there is no such kind

of call drop before:

【Alarm Information:】none.

【Cause Analysis】 From log data and product code, we found it is caused by an inproper

process mechanism in the board GOUc. And this problem is triggered when

switch on Direct Tunnel (One Tunnel) in CN.

In the sceanario of Direct Tunnel, after RAB release due to User Inactive,

according to protocol, resoures of RAN side will be released, but PDP context

will be reserved between SGSN and GGSN. In the procedure of connection

reestablishment between SGSN and GGSN, GGSN will set the address of User

plane to SGSN. GTPU packet from GGSN will be sent via SGSN. Different to

single-core board, multi-core board GOUc will check the IP packet from source

at this time, and the result will be failure. So an Error Indication will be

triggered. Thus generate a GTPU Failure caused call drop.

【 Handling Process: 】 R&D had fixed this problem in the RNC version of

BSC6900V900R011C00SPH732 . After upgrade the RNC version, the problem solved.

【Suggestions and Summary】 When we meet some special value of drop calls, we should open

a ticket to R&D to analyze it. For us, it is better to read the document of precaution.