[Freeswitch-dev] Handling of multiple 183 responses with different SDP

Anthony Minessale anthony.minessale at gmail.com
Wed Oct 27 08:51:55 PDT 2010

Mentioning that it works with asterisk is essentially admitting that its wrong.

Trying to use RFC as an excuse to make me change something annoys me
so let me have my turn now:

RFC 3261  section 13.2.1 bullet 2:

"If the initial offer is in an INVITE, the answer MUST be in a reliable
non-failure message from UAS back to UAC which is correlated to that
INVITE.  For this specification, that is only the final 2xx response to
that INVITE.  That same exact answer MAY also be placed in any
provisional responses sent prior to the answer.  The UAC MUST treat the
first session description it receives as the answer, and MUST ignore any
session descriptions in subsequent responses to the initial INVITE."

ADOPTED RFC vs expired draft.

So that's the end I guess unless you want to email
consulting at freeswitch.org and file a bounty for a non-standard

On Wed, Oct 27, 2010 at 6:15 AM, Irina Ivanova <i.ivanova at mastervoice.it> wrote:
> Hi! We are getting the same problem as described in the jira ticket with
> key FS-715:
> http://jira.freeswitch.org/browse/FS-715?page=com.atlassian.jira.plugin.system.issuetabpanels%3Aall-tabpanel
> 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
> 13.1 Overview
> "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:
> http://tools.ietf.org/html/draft-ietf-sip-183-00
> 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?
> Thanx,
> Irina
> --
> ================================================================
> Distinti saluti
> --
> Irina Ivanova
> Settore Sviluppo MasterVoice
> tel: +39 0522 1846007
> fax: +39 0522 331673
> mob: +39 334 6449290
> e-mail: i.ivanova at mastervoice.it
> web: www.mastertraining.it - www.registroelettronico.com
> Master Training S.r.l.
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Anthony Minessale II

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