I had three SIP endpoints ,
1) x-lite soft phone in my Notebook
2) eMTA
3) Stollmann ITA
-> I could call both eMTA and Stollmann ITA from the soft phone I have in my notebook but the eMTA and Stollmann ITA could not call each other , First I though may be some route is missing but it was not the case , because all three endpoints could register with the SIP server. Then I captured the SIP packets at the SIP server and found the message "415-Unsupported Media Type"... ha ... got it,
Then I checked the capabilities of two devices ,
eMTA - Only supports PCM u-Law
Stollmann ITA only support PCM A-Law
The x-lite soft phone supports many media types , thats why It could call and receive calls form both
you can find these info in the SIP invite message ,
SIP --> Message body --> Media Attribute
