SIP Trunk issue with DT

[hunter]

Hi All,

We have a Mitel MiVoice Business installation in Macedonia and it uses SIP trunk to local telco. All are OK except outgoing international call setup. Local Telco delivers all international outgoing call requests to Deutsche Telecom (without further handling). DT immediately sends a "400 Bad Request" message and clears the call. Local Telco says that DT does not support G729 and ask us to restrict SIP Trunk codec setting to G711 a / u only. We did and nothing changed. Seems that some other parameter in SDP Options etc causes the issue. Does anybody have any idea please?

Regards,

[VinceWhirlwind]

Take a packet capture of a failed call. (If you use the MBG, it's easy through the MBG to kick off the packet capture).
Then open the capture in Wireshark, click "Telephony", then "VOIP Call" then select the call and hit "Flow Sequence". This should help you see which part of the SIP negotiation leads to the error.
 
The kinds of things you can look for are,
CODEC=G711, ptimer=20, t38=off