Technically the SDP i posted does not conform to this, but then there is RFC3264 8.2:

Existing media streams are removed by creating a new SDP with the port number for that stream set to zero.  The stream description MAY omit all attributes present previously, and MAY list just a single media format.

 

So which RFC takes precendence? If it’s RFC8866 5.7 then the device is doing something wrong, but if it’s RFC3264 8.2 and i understand it correctly so that the device can omit even the „c=“ line (… The stream description MAY omit all attributes present previously…) then i would argue that kamailio is doing something wrong.

My reading of this would be that just attributes (`a=` lines) may be omitted. The connection address (`c=` line) is not an attribute, and so still must be present, either at the session level or at the media level.

Although in practice it really doesn't make sense to have an address for a rejected media, and a lenient parser may want to accept it anyway.

Cheers