In practice, there is no "typical" way of putting a call on hold. The very meaning of that action is highly dependent on what you are looking at. If you are looking at signaling coming from an IP phone, you seldom get a=sendonly when someone is placing a call on hold. You will only see that when someone is playing music on hold, which is more common for a PBX or CPaaS. IP Phones normally do not play music on hold so you will see an a=inactive or c=IN IP4 0.0.0.0 IP address. With CPaaS or PBX to an IP phone, you will see a=sendonly or a=inactive, depending on if the music on hold is configured. When communicating with a VoIP service provider over s SIP trunks with SBC, it is unlikely you will see any signaling, IP, or SSRC changes when a call is placed on hold. If you are directly dealing with IMS or RCS environments, you will be overwhelmed with wonder when trying to decipher the reasoning behind each signaling scenario.
So, YMMV _____________ Roman Shpount On Mon, Oct 10, 2022 at 10:17 PM Dale R. Worley <wor...@ariadne.com> wrote: > Ranjit Avasarala <ranjitka...@gmail.com> writes: > > Another way to check is the SDP. for hold music, the media attribute > will > > be sendonly. where as for regular voice traffic it will sendrecv > > Yes, the "typical" way to tell that the far end has put you on hold is > that they will send you a=sendonly in the SDP. Of course, that isn't > guaranteed to be done, but at least it is what people expect and many > systems conform to that. > > In regard to trying to determine on-hold status from the RTP, that is > not reliable. If you can detect that the far end is sending music, it > has likely put you on-hold. But somtimes there are voice announcements > during on-hold. > > Dale > _______________________________________________ > Sip-implementors mailing list > Sip-implementors@lists.cs.columbia.edu > https://lists.cs.columbia.edu/mailman/listinfo/sip-implementors > _______________________________________________ Sip-implementors mailing list Sip-implementors@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
