Hi Gang,
On Thu, Jun 25, 2009 at 5:37 AM, Gang Liu <gangban.lau at gmail.com> wrote:
> Why do you think they breaks RFC? It depents on UA implementation how to
> handle reInvite.
> Maybe ask your provider use another keep-alive method like UPDATE without
> SDP.
>
They are using re-INVITEs as a hacky kind of keep-alive check, but there are
no session-expires headers / timers anywhere. As far as I understand it (but
I'm not a SIP expert yet), re-INVITEs are to be sent when session timers are
in use, or when the party wants to renegotiate SDP (IP or port change, etc).
I'm pretty sure I read somewhere that the remote party (my app) should
respond with SDP if parameters have changed since the last negotiation. This
appears to be default behaviour of PJSIP. However, MetaSwitch will hang up
the call if the 200 OK contains no SDP, which seems completely illogical,
even if it's not breaking RFC compliance.
In the end I got it working by:
void call_on_rx_offer(pjsip_inv_session *inv, const pjmedia_sdp_session
*offer) {
pj_status_t status;
const pjmedia_sdp_session *active_local;
pjmedia_sdp_neg_get_active_local(inv->neg, &active_local);
if (active_local) {
status = pjsip_inv_set_sdp_answer(inv, active_local);
}
}
And then I ignore the subsequent on_media_update, which works for this case
although I will in future allow detaching / re-attaching of media transport
to support any SDP changes.
I welcome any information regarding what the RFCs say about this case!
Many thanks,
-Mark
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