We are trying to connect linphone to a Mitel 3300 telephone system.
From the developers of Mitel we got the following complaint:
From looking at the failed calls traces, it would appear that Linphone
SIP stack is not following RFC 3261. The 3300 SIP lineside does not
offer SDP in the initial invite and the Linphone does not like this nor
does it respond back accordingly. It should offer it's SDP capabilities
when it receives an INVITE without SDP. When the 3300 creates the
initial INVITE, the transaction rules surrounding SDP are:
RFC 3261 13.2.1 Creating the Initial INVITE For the initial INVITE
transaction, the rules are:
1- The initial offer MUST be in either an INVITE or, if not there, in
the first reliable non-failure message from the UAS back to the UAC. In
this specification, that is the final 2xx response.
3- If the initial offer is in the first reliable non-failure message
from the UAS back to UAC, the answer MUST be in the acknowledgement for
that message (in this specification, ACK for a 2xx response).
Concretely, the above rules specify two exchanges for UAs compliant to
this specification alone - the offer is in the INVITE, and the answer
the 2xx (and possibly in a 1xx as well, with the same value), or the
offer is in the 2xx, and the answer is in the ACK. All user agents that
support INVITE MUST support these two exchanges.
Are there plans to make linphone more compliant to RFC 3261?