I am really not sure why you need to send payment info. You will know how long the call takes eg difference in ti,e between Invite and Bye? I thought the reason SIP is so great (and it is) is that it is free. It only costs over what is called the last mile, ie from voip to a landline or mobile. I digress... If you what to monitor the duration of SIP calls knowing the destination SIP or landline/mobile then you will need to implement a Back To Back User Agent server. See http://en.wikipedia.org/wiki/Back-to-back_user_agent for more info. Looks like it is avail at: http://www.b2bua.org I haven't used it anyone else? But the basic idea will be to register some call backs in the Call Control Logic. ie every three seconds a call lasts do your propiertry thing. Looks like it is all written in Python so it will be easy to modify if need be. Oliver On 18/09/2007, Hitesh Tewari <htewari@hotmail.com> wrote: > > Hi Oliver, > > What I want to do is to send some proprietary payment info > periodically (eg ever 3 minutes) to the VoIP provider. > I was hoping that I could do a re-INVITE and tag on the > payment info. > > Does the method you indicate below only work for the > Retry-After call? > > Hitesh > > >Have you thought of using a Retry-After parameter as listed at: > >http://www.iana.org/assignments/sip-parameters? > > > Normally a custom parameter is prefxied by a "p" I think, eg pKeepAlive: > > > Further reading the SIP standard at: > >http://www.ietf.org/rfc/rfc3261.txt has found: > > Retry-After: 18000;duration=3600 > > Retry-After: 120 (I'm in a meeting) > > >Can you provide any further info? > > > ________________________________ > Connect and share instantly with the all-new Windows Live Messenger! Windows > Live Messenger