Thanks Paul. Sorry, i didn't get the point that "From the UAC's perspective it can still start toward the UAC as soon as the INVITE is sent.". May i know how UAC can start the RTP as it has not negotiated media parameters with UAS and doesn't know the port. Please be informed that we have SDP in INVITE.
UAC -> UAS (Invite) includes SDP offer UAS -> UAC (100 trying) UAS -> UAC (180 Ringing Require 100rel header is set) includes SDP answer UAC -> UAS (PRACK to 180 Ringing) UAS -> UAC (200 OK to PRACK) UAS -> UAC (200 OK to invite) No SDP UAC -> UAS (ACK to 200 OK for invite) Regards Rajesh On Mon, May 19, 2014 at 4:17 PM, Paul Kyzivat <[email protected]> wrote: > On 5/19/14 10:58 AM, Rajesh wrote: > >> Hi, >> >> In the below call flow, when the UAC and UAS can start transmitting RTP >> packets. I think RTP session can be started after UAS receives PRACK for >> 180 ringing. I would really appreciate your opinion on this. Thanks >> > > The use of 180rel doesn't alter when RTP can start. From the UAC's > perspective it can still start toward the UAC as soon as the INVITE is > sent. From the UAS perspective it can't start toward the UAC until the UAS > has received the offer (the INVITE). There is no reason why the UAS must > wait for the prack. However the UAS might *want* to wait for the prack > before starting to send, since that gives it more assurance that things are > in good shape. > > For instance, if something in the middle is gating the flow of RTP in both > directions until the answer is received, then waiting for the prack will > avoid early media being dropped. > > Thanks, > Paul > > UAC -> UAS (Invite) >> UAS -> UAC (100 trying) >> UAS -> UAC (180 Ringing Require 100rel header is set) includes SDP Body >> UAC -> UAS (PRACK to 180 Ringing) >> UAS -> UAC (200 OK to PRACK) >> UAS -> UAC (200 OK to invite) No SDP >> UAC -> UAS (ACK to 200 OK for invite) >> >> >> Regards >> Rajesh >> _______________________________________________ >> Sip-implementors mailing list >> [email protected] >> https://lists.cs.columbia.edu/mailman/listinfo/sip-implementors >> >> > _______________________________________________ > Sip-implementors mailing list > [email protected] > https://lists.cs.columbia.edu/mailman/listinfo/sip-implementors > _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
