[Sip-implementors] 3PCC re-connecting scenario
amarabs at gmail.com
Wed Sep 7 13:45:09 EDT 2005
1. re-INVITE with no media should not cause an offer to be sent. As this
state will be offer received, you can't not make an offer when you received
an offer itself. Most of the endpoint consider re-INVITE with no-media
as equivalent to the re-INVITE without offer, Thus they end up in sending
an offer, which is not correct behaviour. According RFC 3264 if Offer
zero "m" lines then answer to that MUST contain zero "m" lines.
Support for RFC 3725 needs to given to the endpoints,
otherwise there may be serious interoperability issue between endpoints
and all 3pcc controller.
But the issue over here is that as per the RFC2327 (section 6.SDPSpecification)
there m-lines are mandatory parameter in the SDP body. Thus if an end point
received INVITE with-out media(zero m-lines), it will reject the request
406 Not Acceptable.
Same senario with the RFC 3264 and 3725 will work with-out any problem.
is a significant gap between 3264 and 2327. I didn't find any documentation
This gap may cause interoperability issue between endpoints and all
This is creating confusion which one to follow. This is an issue which needs
to be taken care.
On 9/1/05, Tina K <kramarv at gmail.com> wrote:
> we are developing the application for re-connecting parties taken from 2
> different calls. Initially I was thinking about inviting first party with
> no_media SDP, 200-ACK, then re-INVITE B-party with no media, obtain offer,
> re-INVITE A with SDPb. Then A answer with SDP a' which will be sent to B
> within ACK:
> <----------INVITE (SDP no_media)
> ---------> 200
> ----------------->INVITE (no SDP)
> <-----------------200 (SDPb)
> <---------------INVITE (SDP b)
> -------------->200 (SDP a)
> -------------------------> ACK (SDP a)
> 1. re-INVITE with no_media causes offer in real life (despite RFC 3725). I
> suppose some Media Gateways will send BYE upon reception ACK without an
> 2 . ACK (SDP a) - the call may end up by generation a BYE by B-party.
> Let' say I send first INVITE with idisabled media (a=sendonly or inactive)
> get 200 with SDPa and send ACK. However, the second problem seems to me
> Any ideas how to avoid ACK with SDP?
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> Sip-implementors at cs.columbia.edu
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