it's legal to get responses with different to-tags, since the request is forked. this is what's happening in this scenario. I think this is an issue of UAC/rtpengin how it is reacting to the second SDP in 183
are the SDPs in 183 responses carried reliably? On Fri, Aug 27, 2021 at 2:51 PM Yuriy Gorlichenko <[email protected]> wrote: > Hello. > The first thing: to tag can't be changed due session once it passed. > > If provider uses forking mechanism the it has to be hidden from your > system. > > Regarding SDP according > https://datatracker.ietf.org/doc/html/rfc3261#section-13.2.1 > They can't change SDP answer description on the fly. Only first SDP answer > used as proper, all othe answers will be ignored. > > On Fri, 27 Aug 2021, 11:27 B. Tietz, <[email protected]> wrote: > >> Hello, >> >> following situation. >> I have a Kamailio (5.4) using rtpengine to loadbalance calls. >> >> If a call from Alice comes in, Kamailio decides to send the call to >> Carrier B from Bob. >> Bobs Phone is ringing and the carrier B send a 183 Session Progress with >> SDP and To-tag=abcd. The SDP has G722 as codec and port 1234. >> A few moments later carrier B send a second 183 Session Progress with SDP >> and TO-tag=fghi. The SDP has G711 as codec and port 5678. This is done, to >> play some funky music as ringtone -.- >> If Bob answers the call, carrier B sends a 200 OK WITHOUT SDP and >> TO-tag=abcd. So this should instruct our Kamailio to switch to the first >> G722 and port 1234. >> >> But sadly, this is just not working as expected. >> >> We tried to set the flags media-handover and port-latching for the >> rtpengine options and additionally set a to-tag when using rtpenging_manage. >> But this doesn't solve the codec change, so we have only audio when Bob >> answers the call, but no ringtone-music. If we allow G711 only in the >> outgoing INVITE to Bob, we have also tha ringtone-muisic, because there is >> no codec-change. >> >> Carrier B tells us, they are using a fork-mechanism. >> >> Is there something we can do, to support the codec change in 183? Or >> enforce carrier B to send SDP in 200 OK? Or anything else? >> >> Carrier B can not change anything in the ringtone-music-backend. They are >> stuck on G711. >> >> Thanks! >> __________________________________________________________ >> Kamailio - Users Mailing List - Non Commercial Discussions >> * [email protected] >> Important: keep the mailing list in the recipients, do not reply only to >> the sender! >> Edit mailing list options or unsubscribe: >> * https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users >> > __________________________________________________________ > Kamailio - Users Mailing List - Non Commercial Discussions > * [email protected] > Important: keep the mailing list in the recipients, do not reply only to > the sender! > Edit mailing list options or unsubscribe: > * https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users > -- Arsen Semenov
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