The local office uses SoftCo5816 (V100R002C04SPC700), and the peer office uses eSpace U2990. The calling number is 69091056, and the called number is 69699717.
After initiating a call, the calling party hears the normal call waiting announcement. However, when the called party picks up the phone, the called party hears the announcement indicating the call is disconnected and the calling party hears "sorry, the number you dial has not logged in."
Step 1 Run the config modify sip parameter usesessiontimer yes command to enable the sessiontimer parameter. The fault still exists.
Step 2 Capture SoftCo logs. According to the following log information, the message sent by SoftCo has enabled the sessiontimer function.
CSeq: 3 INVITE
Step 3 Ask core network engineers to help locate the fault. According to the captured logs on the core network, the core network returns 422.
SIP/2.0 422 Session Interval Too Small
Via: SIP/2.0/UDP 18.104.22.168:5060;branch=z9hG4bKlnpa90ak4lpp1i33nlmap0mlm
Step 4 In 422, both the returned error code and error message carry Session Interval Too Small because the minimum interval for carrying a session is smaller than what China Mobile has specified (1800s).
Step 5 Run the config modify sip parameter minsessioninterval 1800 sessioninterval 1800 usesessiontimer yes command to set the minimal interval for carrying a session to 1800s. The fault is rectified.
The possible causes are as follows:
The sessiontimer parameter is disabled.
The minimum session interval on the SoftCo is incorrect.