Mitel 5000 no 200 response

[Patlabor]

Hey folks,

Hopefully somebody is able to help with this query.

We have been contacted by our supplier to say that it's been reported to them that some inbound calls are being rejected due to the following:

"On the call flow one of our customers sends an invite no sdp/late offer, I believe this is what your equipment doesn’t like as calls with sdp/early offer work fine.
 
After you send a 180 SIP response we would then normally expect a 200 response from your end. However the call times out after about 30 seconds. "

If anyone can point me in the right direction to resolve this on the Mitel 5000 it would be appreciated.

[Tech Electronics]

Patlabor,

I don't think a 200 OK response is a valid response to a 180 Ringing. That is, in my opinion, requires a Provisional Response Acknowledgement [PRACK], which would be PRACK that would then get a Response of 200 OK.

The 200 OK Response after a Provisional Message, such as 100 Trying, 180 Ringing, 181 Forwarding, etc.., would be typically be for the INVITE message sent previously; 200 OK INVITE. In that case it means the call was answered by either the person picking up the ringing phone or voice mail answering. In the case you described the caller, the one who sent the INVITE, disconnected from the call prior to it being answered.

Read up on RFC 3665 page 11. https://tools.ietf.org/html/rfc3665

3.1.  Successful Session Establishment


   Alice                             Bob
     |                                   |
     |       INVITE F1              |
     | ----------------------->  |
     |    180 Ringing F2          |
     | <-----------------------  |
     |                                   |
     |       200 OK F3             |
     | <-----------------------  |
     |         ACK F4                |
     |  -----------------------> |
     |   Both Way RTP Media   |
     |<=============>|
     |                                   |
     |         BYE F5                |
     | <-----------------------  |
     |       200 OK F6             |
     | ----------------------->  |
     |                                   |


Thanks,

TE