[SR-Users] RTPengine with rejected RE-INVITE when port is changing

Daniel-Constantin Mierla miconda at gmail.com
Thu Dec 5 11:45:54 CET 2019

On 05.12.19 11:33, Daniel Tryba wrote:
> On Thu, Dec 05, 2019 at 09:37:51AM +0000, Laurent Schweizer wrote:
>> Hello,
>> I already see old post about this :
>> https://opensips.org/pipermail/users/2014-November/030451.html
>> but I???m interested to know if now they is a solution ????
>> so the issue is a RE-INVITE rejected (415 Unsupported Media or 488 ) and the RTP port is changing.
>> Is that case the old RTP relay (I???m using RTPengine) is destroyed after 30sec.
>> Any way to restore them ?
> I'm confused:
> - opensips != kamailio
> - rtpproxy != rtpengine
> But RFC 3261 states (page 16):
>    During the session, either Alice or Bob may decide to change the
>    characteristics of the media session.  This is accomplished by
>    sending a re-INVITE containing a new media description.  This re-
>    INVITE references the existing dialog so that the other party knows
>    that it is to modify an existing session instead of establishing a
>    new session.  The other party sends a 200 (OK) to accept the change.
>    The requestor responds to the 200 (OK) with an ACK.  If the other
>    party does not accept the change, he sends an error response such as
>    488 (Not Acceptable Here), which also receives an ACK.  However, the
>    failure of the re-INVITE does not cause the existing call to fail -
>    the session continues using the previously negotiated
>    characteristics.  Full details on session modification are in Section
>    14.
> So if this happens with kamailio/rtpengine that is a bug in (I  presume) rtpengine.

RTPEngine itself doesn't send SIP replies. Typically the 415 or 488 are
sent by the endpoints. Kamailio doesn't do it by default, but of course
can do it if explicitely wanted in the kamailio .cfg routing actions. My
guess is that the endpoint sends the 415/488, so all this doesn't have
to do anything with rtpengine/kamailio -- that can be checked by looking
at the sip network traffic on kamailio server to see where 415/488 is
coming from.


Daniel-Constantin Mierla -- www.asipto.com
www.twitter.com/miconda -- www.linkedin.com/in/miconda
Kamailio World Conference - April 27-29, 2020, in Berlin -- www.kamailioworld.com

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