SIP-H.323 Interworking Call Scenarios

[VIPIN PALAWAT]

Hello Radhika,

We too feel that it is better to come up with a proposal as early as
possible without adding much complexity to it.
I fully agree with you and Kundan singh on this point.

Somethings more that I would like to be added to either initial or expanded
scope (preffered) of the  TOR are:
1) H.245 tunnelling in H.323
2) Pre Granted ARQ in H.323
3) Overlapped Sending in H.323
4) Single line extension in SIP

Are you in  favour of giving a detailed call scenario examples covering all
the possible call scenarios as per initial
scope of the TOR . This will be something similar to the latest draft
"draft-ietf-sip-call-flows-00.txt" .

I am lokking for your comments.

Best Regards
Hemant Agarwal
Vipin Palawat



----- Original Message -----
From: Roy, Radhika R, ALARC <rrroy at att.com>
To: Kundan Singh <kns10 at cs.columbia.edu>; Hemant Agrawal
<hemantag at graffiti.net>
Cc: <schulzrinne at cs.columbia.edu>; <jdrosen at dynamicsoft.com>;
<korpim at sbs.de>; <karl.klaghofer at vs.siemens.de>; <alan.johnston at wcom.com>;
<steven.r.donovan at wcom.com>; <Kevin.Summers at wcom.com>;
<dean.willis at wcom.com>; <henry.sinnreich at wcom.com>; VIPIN PALAWAT
<vipin.palawat at wipro.com>; <agboh at helios.iihe.ac.be>;
<Robert.Sparks at wcom.com>; <Chris.Cunningham at wcom.com>; <orit at radvision.com>;
<taylor at NORTELNETWORKS.COM>; <joon_maeng at vtel.com>;
<drwalker at ss8networks.com>; <paul.jones at TIES.ITU.INT>; Dilber, Ayse, ALARC
<adilber at att.com>; <stephen.terrill at ericsson.com>
Sent: Thursday, March 09, 2000 1:00 AM
Subject: RE: SIP-H.323 Interworking Call Scenarios


> Hi, Kundan, Hemant, and Vipin:
>
> It seems to me that Kundan's proposal is quite logical. In our terms of
> reference document (TOR), we can scope our work in a 2-step approach as
> follows:
>
> The initial scope of the TOR:
>
> - Simple SIP--SGW--H.323 translation, with SGW
>   independent of any GK or proxy.
> - Translating (blind) call transfer by endsystems.
> - Translating call forwarding by endsystems.
> - How to handle, SIP re-INVITEs (change in session description/or
> media transport address) and change in H.323 logical channel/mode request.
> - How to handle H.323 fast start.
>
> The expanded scope of the TOR:
>
> - Call hold translation
> - Call transfer/forwarding by GK and/or proxy.
> - SIP--H.323--SIP and H.323---SIP---H.323 scenarios.
> - SGW coexiting with GK or proxy.
> ...
>
>
> Please provide your comments.
>
> Best regards,
> Radhika R. Roy
> AT&T
>
> > -----Original Message-----
> > From: Kundan Singh [SMTP:kns10 at cs.columbia.edu]
> > Sent: Wednesday, March 08, 2000 1:04 PM
> > To: Hemant Agrawal
> > Cc: schulzrinne at cs.columbia.edu; jdrosen at dynamicsoft.com; korpim at sbs.de;
> > karl.klaghofer at vs.siemens.de; Roy, Radhika R, ALARC;
> > alan.johnston at wcom.com; steven.r.donovan at wcom.com;
Kevin.Summers at wcom.com;
> > dean.willis at wcom.com; henry.sinnreich at wcom.com; VIPIN PALAWAT;
> > agboh at helios.iihe.ac.be; Robert.Sparks at wcom.com;
> > Chris.Cunningham at wcom.com; orit at radvision.com;
taylor at NORTELNETWORKS.COM;
> > joon_maeng at vtel.com; drwalker at ss8networks.com; paul.jones at TIES.ITU.INT;
> > Dilber, Ayse, ALARC; stephen.terrill at ericsson.com
> > Subject: Re: SIP-H.323 Interworking Call Scenarios
> >
> >
> > Hi Hemant and Vipin,
> >
> > Its a very good collection of call flows' translation.
> >
> > Few comments:
> >
> > 1) Might want to include H.323---SIP---H.323 case where the
> >   call goes through two SGWs. Since, combining the
> >   two call flows (H.323-SIP, sec:1.1) and (SIP-H.323, sec:2.1)
> >   may not work. The SIP ACK in sec:1.1 has a different session
> >   description, which will trigger some "Mode Request"
> >   and/or "Open/Close LogicalChannel" procedures in
> >   sec:2.1.
> >
> > 2) In sec:1.1,1.2,1.3; it might be better to send ACK
> >    immediately after receiving 200 OK, and send
> >    re-INVITE once H.245 procedures are complete.
> >    This way, we can avoid the retransmissions of 200 OK
> >    by SIP EP if H.245 procedures take more time to complete.
> >    Comments ??
> >
> > 3) In Fast Connect procedures (sec 3.1), I assume that
> >    if the normal H.245 procedure resumes after initial
> >    call setup (with faststart), and there is a change in
> >    H.323 side session description, then appropriate
> >    re-INVITE message is sent to SIP EP.
> >
> > 4) Sec:4 Call transfer may be renamed to (Blind) Call Tranfer.
> >
> > 5) Sec:4.1. RTP should be between SIP EP(B) and SIP EP(C)
> >
> > 6) Sec: 5.1, you may send "181 Call is being forwarded"
> >    response to SIP (A).
> >      Can SIP (A) reject the call forwarding here ???
> >      Who pays for the call if the forwarded call
> >      costs more (longdistance/international) ? Any
> >      pointer to this topic is appreciated.
> >
> > 7) The call forwarding may be initiated by the
> >    proxy (after receipt of 486 Busy Here) or by
> >    the SIP endsystem itself (by responding with 302 Moved Temporarily)
> >    if it is configured to do so. However, that will not
> >    affect the translation much.
> >
> > 8) Sec:5.3, typo; SIP User (A) should be (B) and (B) should be (C).
> >
> >
> > Considering the wide variety of scenarios between
> > H.323 and SIP, would it be reasonable to start with
> > a simple call translation specification,
> > provide a state machine/pseudo code for
> > message handling by the SGW (signaling gateway)
> > and then extend the state machine/pseudo code
> > to handle all the non-trivial call scenarios.
> >
> > Once the basic translation specification is ready,
> > profiles for extensions (e.g., blind transfer
> > using GK, call forwarding using proxy,
> > translating forking proxy behaviour to H.323, etc.)
> > may be specified.
> >
> > Thus, the initial specification may cover following
> > areas:
> > - Simple SIP--SGW--H.323 translation, with SGW
> >   independent of any GK or proxy.
> > - Translating (blind) call transfer by endsystems.
> > - Translating call forwarding by endsystems.
> > - How to handle, SIP re-INVITEs (change
> >   in session description/or media transport address)
> >   and change in
> >   H.323 logical channel/mode request.
> > - How to handle H.323 fast start.
> >
> > Later on other things may be added:
> > - Call hold translation
> > - Call transfer/forwarding by GK and/or proxy.
> > - SIP--H.323--SIP and H.323---SIP---H.323 scenarios.
> > - SGW coexiting with GK or proxy.
> >  ...
> >
> > Motivation for such a separation is to allow
> > the implementors more freedom in deciding what
> > configuration to choose, while still maintaining
> > the basic translation framework.
> > For example, call forwarding to voicemail may
> > be handled by
> > - the endsystem by sending 302 moved, after say 4 rings.
> > - the proxy server on receipt of 486 busy here
> > - the proxy server, forking one branch of the request to the voicemail
> > system which accepts the call after, say, 15 seconds.
> >
> > It turns out that once we have the initial specification,
> > (as mentioned in above list) the advanced scenarios
> > are just a "special cases"/"combination of cases" of the
> > initial scenarios.
> >
> > Regards
> >
> > Kundan
> > --
> > Kundan Singh     http://www.cs.columbia.edu/~kns10
> >
> > On Wed, 8 Mar 2000, Hemant Agrawal wrote:
> >
> > > Hi All,
> > > There was a continuous discussion on the different configuration for
the
> > > SIP - H.323 interworking.
> > >
> > > In our opinion, it would be better if some basic features (like Call
> > > Transfer, Call Hold and Call forwarding) is also added as part of the
> > > discussion.
> > >
> > > We are enclosing some call flow examples of SIP-H.323 interworking.
> > Please
> > > give your comments on these call flows. Our stress is on the call
> > features
> > > and others are just informational. We have specified few issues also
> > inorder
> > > to make these protocols interwork.
> > >
> > > Kindly let us know if you agree to include the feature discussion also
> > as
> > > part of the SIP - H.323 interworking. We are ready to put our efforts
> > for
> > > the feature interworking.
> > >
> > > Best Regards
> > >
> > > Hemant Agarwal
> > > Vipin Palawat
> > >
> > >
> > >