Unstable Status When the Number of Registration Groups Exceeds 100

Publication Date:  2015-07-16 Views:  159 Downloads:  0
Issue Description
SoftCo version: V100R002C04SPC700

Networking: Huawei's SoftCo9500 --> IMS network

The returned registration messages are normal when the number of registration groups is smaller than 100. Once the number of registration groups exceeds 100 and reaches 300, the status of registration groups becomes unstable. This problem still exists after customers change the control board and update the software.
Handling Process
Step 1 Capture and analyze upstream network packets of the SoftCo. The timeout period carried in the SoftCo registration request is 1800s, as shown in the following figure.

Step 2 Check the 200 OK message returned by the IMS network. According to the following figure, the user has changed the timeout period to 30s on the IMS network.

When the timeout period changes to 30s, the SoftCo sends a registration message to the IMS network every 15s (because the registration interval is half of the timeout period). This sharply increases the registration traffic. In response, the IMS network sends a 423 error code to the SoftCo, informing the SoftCo that it cannot respond to every registration message within such a short interval.

Step 3 Change the timeout period from 30s to 1800s. However, the IMS network changes the timeout period to 30s using its 200 OK response message. Constant and abnormal changes of the timeout period lead to the registration failure of some SoftCo users.

Step 4 Conclude the failure reason. The IMS network is running properly, and it is the SBC on the IMS network that is faulty.

Step 5 Change the SBC configurations on the peer office.

Root Cause
The SBC does not reply to SoftCo registration requests.
In most cases, timeout period affects the interconnection between the SoftCo and the IMS network. The timeout period is set to be a little longer when the IMS needs to centrally process provincial user registrations, to reduce registration processing pressure. If the timeout period is set to be very short and the request amount is huge, it is almost possible for the IMS network to process registrations in time, leading to registration failures of some users.