Symptom
When a user under the IAD makes a call to an onsite mobile phone user, the mobile phone user cannot hear the calling party's voice for several seconds. This fault occurs when the traffic is high.
Network:
IAD user-IAD-SBC-UMG
Cause
The defense against UDP Flood attacks is enabled for the SBC.
Solution
1.1.Capture packets on the IAD, between the IAD and the SBC, and between the SBC and the UMG.
2.2.Analyze the captured packets.
The packets from the IAD are normal; however, packet loss occurs during the transmission between the SBC and the UMG. The defense against UDP Flood attacks is enabled for the SBC. UDP packets bear the voice packets. When the traffic is high, the SBC discards the UDP packets that bear voice packets. Then one-way audio occurs.
3.3.Disable the defense against UDP Flood attacks for the SBC.
4.4.Check whether the fault is rectified.
1.1)If yes, the procedure ends.
2.2)If no, go to 5.
5.5.Contact Huawei technical support.
