Subject: SIP architecture question

From: [email-masked]
Date: Fri, 22 May 1998 08:56:50 -0400

I have been studying the SIP protocol and have a question about
architecture assumptions for the location of the SIP client for multimedia
conferencing.

For PINT use, two basic alternatives for a SIP client are discussed:
(assuming SIP is to be used for PINT :-).

1. The PINT client is located at a web server:

     User --- (HTTP) ---> web server/pint client --- (SIP) ---> pint server

2. The PINT client is located at the user's machine:

     User/pint client  --- (SIP) ---> pint server

For multimedia conference use, it is clear that the SIP client is most
likely located at the user's machine. Is this a requirement? Is the
"remote" alternative possible? That is, will SIP work for this application
if it is located at a web server and the communication to the user machine
is through some other mechanism (i.e., HTTP)? Is there some kind of
interaction with SDP and RTP that prevents this?

Can anyone help me out here?

Thanks,
David

-------------------------------------
David Shrader
Bellcore
IN Design and Engineering

---

From: Henning Schulzrinne <[email-masked]>
Date: Fri, 22 May 1998 12:03:18 -0400

> interaction with SDP and RTP that prevents this?

Yes, this will work just fine.

The nice thing about separating session description and call origin is
that the recipient and source of media does not have to be the entity
generating the signaling requests. Thus, a SIP request can well be
triggered from within a cgi script and then direct media elsewhere
(e.g., the client that clicked on the cgi-bin link), assuming that the
web server has done due diligence to avoid becoming the unwitting
perpetrator of a packet-bombing attack.

-- 
Henning Schulzrinne   [email-masked]
Dept. of Comp. Sci.   ph  +1 212 939-7042
Columbia University   fax +1 212 666-0140
New York, NY 10027    http://www.cs.columbia.edu/~hgs