SIP Trunk problems with CME

[nurhat19921]

Hello! I have some problems with SIP Trunk when I call to local city numbers from cisco 3905 7821 sip phones. I attached sip debug. Please help me!

[Vivek Batra]

Hi,

I tried to check when exactly router prints this error but didn't found any trusted reference.

To demonstrate to your provider is only RFC 3264 reference. If they don't agree, then checking with TAC seems only option.

- Vivek

[Jonathan Unger]

Hi Vivek,

In the initial INVITE from the phone to the CME, the phone specifies the following allowed methods:

Allow: ACK,BYE,CANCEL,INVITE,NOTIFY,OPTIONS,REFER,REGISTER,UPDATE,SUBSCRIBE,INFO

As seen above there is no PRACK, in the Allow list.

However, in the trace we can also see that the CME sends a 183 Session Progress with SDP to the phone and the phone does not respond to the session progress.

Shortly after, there is a "500 Internal Server Error" sent to the phone.

Do you think that the Internal Server Error could be caused by the phone not responding to the CME 183 session progress?

- Jon

[Vivek Batra]

Hi Jonathan, I don't think the issue is because of what you have mentioned. This is because whether PRACK should be used or not depends on 100rel extension conveyed by UAC (phone in this case) in either 'require' or 'supported' header. In this call flow, phone has not conveyed usage of PRACK as there is no 100rel extension in INVITE message (from phone to CME). My doubt is there is something wrong with 180 Ringing received from service provider since as soon as CME receives 180 Ringing, it sends 500 Internal Error to phone. Let me check the logs of working and non working call if I can figure out any thing. In the meanwhile, I will request the OP to disable 100rel in CME so that we can avoid using PRACK between CME and provider to see if it makes any difference.

[samsam926]

Done