Subject: [Sip] about H.323 and SIP

From: "Na Li" <[email-masked]>
Date: Wed, 12 Sep 2001 19:15:35 -0500

Hello,
 
I have several questions relating to H.323
 
1) What's the fundamental difference between H.323 (including fast
setup) and SIP? I don't mean the text encoding or ANS.1 encoding. 
2) Could Media gateway controller use H.323 for session creation, and
use Megaco to communicate with media gateway?
3) Is any standard there to map H.323 with SIP?
 
Thanks, have a nice day
 
Lina

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---

From: "Michel A. Maddux" <[email-masked]>
Date: Thu, 13 Sep 2001 08:45:30 -0500

>>setup) and SIP? I don't mean the text encoding or ANS.1 encoding.

Actually, there isn't a single fundamental difference.  There are many
differences, and yet, both protocols objective at the highest level is the
same - call setup, management - teardown.  Perhaps you would like to refer
to a couple of the papers that are posted on the Columbia web-site.  There
have been several papers developed on the SIP-H.323 comparison.

To me, the fundamental difference is in the use of a single message (INVITE)
on the SIP side, compared to the multiple message traffic (e.g. ARQ, LRQ,
and so on) required to setup the calls.  There are many other differences as
well, so the challenge in mapping the two protocols is to determine from a
functional level the intent of the caller and map to the appropriate call or
sequence of calls on the other side.

>>use Megaco to communicate with media gateway?

Well, I suppose anything is possible.  Why do you want to do it that way?

>>3) Is any standard there to map H.323 with SIP?

Check the internet drafts already available on this subject.

thanks. /m.

Michel A. Maddux
CEO and Lead Guitarist
*:  719-686-9733
*:  719-337-4727 Mobile
*  [email-masked]
*  PO BOX 3087
      Colorado Springs, Colorado 80934

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From: "Cullen Jennings" <[email-masked]>
Date: Thu, 13 Sep 2001 08:07:42 -0700

In order of easy to hard the answers are:

Question #3 - There are some drafts and a mailing list at
[email-masked] - At www.vovida.org there is a program that does
the simple cases of SIP to H323 interworking and is open source if you want
to look at how it works.

Question#2 - yes - and I imagine some will. It seem likely there will be
controllers that can talk SIP and H.323 and control a Megaco gateway.

Question #1 - ask 5 people, get 10 answers :-) Religion might be the most
consistent answer. This is hard to pin down (keep in mind you asked on a SIP
mailing list not a H.323 list so there may be some tiny bias in the answers
you get). For me, one of the key advantages of sip is that I think it will
be easier to create advanced services and features in it. There are many
other issues like scalability and building 99.999% available systems.

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]]On Behalf Of Na Li
> Sent: Wednesday, September 12, 2001 5:16 PM
> To: [email-masked]
> Subject: [Sip] about H.323 and SIP
>
>
> Hello,
>

---

From: "Paul Long" <[email-masked]>
Date: Thu, 13 Sep 2001 11:15:30 -0500

Michael,

If the H.323 endpoint is unregistered or uses the direct call model and
pregranted ARQs, only a single message (Setup) is necessary in H.323 to
setup a call.

Paul Long
ipDialog, Inc.

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]On Behalf Of Michel
A. Maddux
Sent: Thursday, September 13, 2001 8:46 AM
To: 'Na Li'; [email-masked]
Subject: RE: [Sip] about H.323 and SIP

thanks. /m.

Michel A. Maddux
CEO and Lead Guitarist
*:  719-686-9733
*:  719-337-4727 Mobile

---

From: "Michel A. Maddux" <[email-masked]>
Date: Fri, 14 Sep 2001 08:52:29 -0600

Paul Long writes:

--------------

Hmmm, and yet, the need to have the pre-granted ARQ is part of the call
setup
sequence... and in fact, depending upon exactly how the Gatekeeper bandwidth
management is provided, could itself cause some problems.  For example, if
1000 endpoints all request a pre-granted ARQ (this is after registration
sequence
and etc...), and the Gatekeeper allows only 1000 calls - no calls are in
progress at that time, and yet the gatekeeper could disallow the next
request.

Clearly, pre-granted ARQ and Fast Start are examples of the changes to the
original H.323 spec which were specifically designed to address the issues
of excessive message traffic.  My comment to Lina in the original post was
not intended to describe the many intricacies of the two protocols (because
I believe that they both have a place in the industry), rather to point out
what I believe to be the fundamental difference between them - pursuant to
the question.

thanks. /m.

---

From: "Paul Long" <[email-masked]>
Date: Fri, 14 Sep 2001 13:21:39 -0500

Michael,

No, the pregranted ARQ is part of the registration process and is not
involved with call setup. Let me say it again, call setup can be
accomplished with a single message, so H.323 is no different than SIP in
this regard.

Also, H.323 and SIP have influenced each other, so it's not by any means a
one-way street.

Paul Long
ipDialog, Inc.

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]On Behalf Of Michel
A. Maddux
Sent: Friday, September 14, 2001 9:52 AM
To: 'Paul Long'; [email-masked]
Subject: RE: [Sip] about H.323 and SIP

Paul Long writes:

thanks. /m.