[Freeswitch-dev] Handling of multiple 183 responses with different SDP
i.ivanova at mastervoice.it
Wed Oct 27 04:15:03 PDT 2010
Hi! We are getting the same problem as described in the jira ticket with
Our provider is also sending us more than one 183 Session progress
response, each of them with SDP where destination IP address is the same
but the UDP ports are different.
If is needed I can provide the pcap file where you can see that after
receiving of second 183 Session progress response (with updated SDP)
Freeswitch continues to listen on an old port. As a consequence, no
audio can be heard.
Our provider assures us that sending of more than one 183 Session
progress responses is completely standard behavior that does not violate
SIP RFC 3261 and is handled correctly by any ATA VoIP.
We verified the Asterisk behavior in this case, and can say that it
handles receiving of multiple 183 Session progress responses without any
problems and changes the UDP port each time it gets changed in session
description inside of 183 response.
Our provider gave us a reference to SIP RFC 3261:
13 Initiating a Session
"Before sending a final response, the UAS can also send provisional
responses (1xx) to advise the UAC of progress in contacting the called user.
After possibly receiving one or more provisional responses, the UAC will
get one or more 2xx responses or one non-2xx final response."
"one or more provisional responses" was underlined by our provider and
in addition to this was said that there is no any place in RFC from
which you can conclude that you can not send more than one SIP 183
Session Progress response.
We also found a document regarding 183 response:
Here are some references to the parts talking about temporary media and
session description change:
4.2. Change of Temporary Media
After a temporary media stream has been established, its parameters
can be changed by sending further provisional responses that also
contain session descriptions. Upon receipt of such a response, the
client MUST immediately cease transmission of media relating to the
old temporary stream. As before, the new temporary media stream is
established after acknowledgement of the provisional response.
Provisional responses which contain no session description SHOULD NOT
have an effect on any currently established temporary media stream.
5.11.7 Caller Receives 183 Response
When the calling UA receives a 183 response that contains a session
description and an indication that the session description is for
early media, it SHALL setup the associated media session and present
any media received from the called UA to the user.
Again nothing is said about multiple 183 responses specifically, only
about multiple provisional responses in general.
So, is there anything that can be done to resolve this issue?
Settore Sviluppo MasterVoice
tel: +39 0522 1846007
fax: +39 0522 331673
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e-mail: i.ivanova at mastervoice.it
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