The topology is:
Customer planned to use a NE20 to replace AR28,adding E1 links,from 12*E1(one MP-GROUP) to 36*E1(three MP-GROUP).Before replacing,customer's bandwidth was 7M around,but after replacing,the bandwidth is less than 3M,which is much less than before.
1.After we rollbacked with AR28,everything was normal,so I exclude the cause 1.
2.As before rollback,nothing was changed on BSC.Between BSC and PDSN,everything is transparently transmitted.So cause 2 is excluded.
3.Checking configuration on NE20,we found that customer configured load-balance by packet,in addition,the MP interfaces on NE20 were not
configured ppp mp recorder function.Hence,packets were out of order during transmission,caused retransmission,and then caused the TCP rate auto-decreasing.
4.Correct the configuration on MP interfaces,enable the ppp mp recorder function,and execute the "restart" or "shutdown" and "unshutdown" command.
5.Everything was OK then.
It's obvious that the packets lost,so I conclude the reason are following:
1.Transmission equipment has problem.
2.BSC has problem.
3.Configuration on NE20 has problem.
When you configure the ppp mp recorder function,do please execute the "restart" or "shutdown" and "unshutdown" command.Then the function will be activated.