Subject: RE: question about H.323/SIP and MDCP/MGCP

From: "Hoefelmeyer, Ralph (MCI)" <[email-masked]>
Date: Wed, 24 Mar 1999 23:52:08 -0000

Hanlin,

As I understand them -

1) the MDCP/MGCP protocols control devices and provide bridging between the
SS7 world and the network world

2) We could use one or the other of the protocols for both internal and
external signaling if they are extended to allow the use of scripts, maybe
like VXML or Perl or ?

3) MGCP can do call setup, but the MCG is always in the call stream for the
duration of the call, making scalability an issue.  It is good for
connection to the PSTN.

These questions are the basis for the current holy wars raging on which
protocol to use for what purpose.

Ralph

> -----Original Message-----
> From:	[email-masked] [SMTP:[email-masked]]
> Sent:	Wednesday, March 24, 1999 4:17 PM
> To:	list iptel
> Subject:	question about H.323/SIP and MDCP/MGCP
> 
> 
> 
> I have couple of questions about both signalling protocols in VoIP.
>    Why we need separate protocols for internal signalling (MDCP/MGCP) and
>    external signalling (H.323/SIP)? Can we use H.323/SIP or MDCP/MGCP for
> both
>    external and internal signalling?
>    If not, why? By my understanding, MDCP/MGCP have nothing to do with
>    end-to-end call setup, even there is callID field in their connection
> setup
>    messages. Is this right? Any other issues?
>    Why H.323/SIP can do it either?
> 
> Any comments are appreciated!
> 
> Hanlin
> 
> 
> 
> ---------
> This message came from the IETF IPTEL Working Group Mailing List.

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From: "Vipin Palawat" <[email-masked]>
Date: Thu, 25 Mar 1999 09:20:30 +0530

Hello Hanlin,

I think you are slightly confused with H.323/SIP, MGCP/MDCP.

In fact SIP is a proposed alternative to H.323 due to its light weight
nature and sort of HTML message flows.
Also the call setup procedures in SIP are simpler as compared to
H.323.

On the other hand MGCP is basically suited for Call agent and has
some plus points in comparison with H.323.

But you can have a complete VOIP product suite with H.323 itself.

Regards
Vipin

________________________________________________
Have  a  Nice  Day!!!

Vipin  Palawat
Wipro  Infotech :Enterprise Solutions (Telecom Division)
K-312, 5th Block , Koramangala,
Bangalore - 560 095 (India)
Ph: 91-80-5538301 Extn:2431
mailto:[email-masked]

-----Original Message-----
From: [email-masked] <[email-masked]>
To: list iptel <[email-masked]>
Date: Thursday, March 25, 1999 5:00 AM
Subject: question about H.323/SIP and MDCP/MGCP

Hanlin

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From: Ami Amir <[email-masked]>
Date: Thu, 25 Mar 1999 14:24:58 +0200

Dean,

Well, as an old time H.323 person. When I see what is happening to SIP
(which was positioned as a simple alternative to H.323) - the same argument
can be put forward - that once the real functions are provided for, SIP
tends to become closer and closer to H.323.

;-)

Ami Amir

	-----Original Message-----
	From:	Dean Willis [SMTP:[email-masked]]
	Sent:	Thursday, March 25, 1999 8:42 AM
	To:	[email-masked]; 'list iptel'
	Subject:	RE: question about H.323/SIP and MDCP/MGCP

	Actually, it is quite conceivable to use SIP for everything, you
just
	have to morph the call model into something the telco kiddies don't
	understand and it makes their heads hurt. Trust me on this one, I
spend
	a lot of time explaining the concepts to serious bellheads, and it's
not
	easy. They think "big switch in network controls all stupid
endpoints".

	Even with MxCP, my thoughts are to use it only as a "local bus"
protocol
	between a gateway controller (read "SIP User Agent") and a bunch of
	gateway ports. Even here, it begins to make less sense as the scope
of
	MxCP increases -- eventually, the code size/complexity of MxCP will
be
	greater than that required to run SIP on the gateway port,
eliminating
	the basic cost-reduction goal of the original project (any of you
	developers have a code base to compare?).

	I think the people who want to use MxCP to "control" handsets on
	somebody's desk are way off-base. I assert that no informed user
wants
	their Internet device to be slaved to a carrier's Class-X switch (or
	SCP). A peer-to-peer model is far more palatable for the general
case.
	Furthermore, selection and application of various third-party call
	features should be at the end-user's discretion, not Ma Bell's
(insert
	favorite legacy telco perjorative here) and slave devices tend to
	require support from the Big Switch to bring in third-party
services.

	Let's keep the network stupid and the end devices smart!

	--
	dean

	Disclaim: These are my own opinions. Some of my coworkers disagree
	greatly. Some of them even discuss topics on this list . . .

	-----Original Message-----
	From: [email-masked]
	[mailto:[email-masked]]On Behalf Of
	[email-masked]
	Sent: Wednesday, March 24, 1999 5:17 PM
	To: list iptel
	Subject: question about H.323/SIP and MDCP/MGCP

	I have couple of questions about both signalling protocols in VoIP.
	   Why we need separate protocols for internal signalling
(MDCP/MGCP)
	and
	   external signalling (H.323/SIP)? Can we use H.323/SIP or
MDCP/MGCP
	for both
	   external and internal signalling?
	   If not, why? By my understanding, MDCP/MGCP have nothing to do
with
	   end-to-end call setup, even there is callID field in their
connection
	setup
	   messages. Is this right? Any other issues?
	   Why H.323/SIP can do it either?

	Hanlin

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From: Bob Bell <[email-masked]>
Date: Thu, 25 Mar 1999 08:07:13 -0700

Just a comment on this response.

First, the MGCP/MDCP or Megaco protocol controls devices which includes ss7
gateways but is not limited to same.

Second, scripting is a desirable feature but is not as yet defined in the
protocol under development. It is wanted, but not yet available.

Third, the MGC is only in the call stream from the call control perspective not
the information flow (RTP streams).
At 04:52 PM 3/24/99 , Hoefelmeyer, Ralph (MCI) wrote: 

> duration of the call, making scalability an issue.  It is good for connection
> to the PSTN.
>
> -----Original Message-----  From:   [email-masked]
> [SMTP:[email-masked]]  Sent:   Wednesday, March 24, 1999 4:17 PM
To:   
>  list iptel  Subject:        question about H.323/SIP and MDCP/MGCP 
>
>
>
Why we
> need separate protocols for internal signalling (MDCP/MGCP) and     external
> signalling (H.323/SIP)? Can we use H.323/SIP or MDCP/MGCP for both    
> external and internal signalling?     If not, why? By my understanding,
> MDCP/MGCP have nothing to do with     end-to-end call setup, even there is
> callID field in their connection setup     messages. Is this right? Any other
> issues?     Why H.323/SIP can do it either? 
>
> ---------  This message came from the IETF IPTEL Working Group Mailing List. 

Bob Bell
Distinguished Member of the Technical Staff
Cisco Systems Inc.
801-294-3034(v)
801-294-3023(f)

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From: [email-masked]
Date: Wed, 31 Mar 1999 09:14:47 -0600

Hanlin,

This was part of a message Tim Miller sent over megaco mailing lists. I think
his mail gives reasonal insight into/concerns about SIP/H323 Vs MDCP/MGCP
issues. In adition to to the explanations from Douglas and Stephen this will
give a big picture of where SIP/H323 and MDCP/MGCP fit into VOIP...

"......My view is that one can have an MGC-MG control protocol without ever
mentioning H.323, ETSI TIPHON, or SIP. And if we had restricted our scope
to this as the charter suggests, we would not have all of these requirement
and definition problems proliferating the mail exploder. There seems to be
belief among the H.323 and ETSI TIPHON people that the MGCP backers want to
KILL H.323. Having friends and colleagues among both groups, that simple is
not the case. The truth is that some Network Service Providers or MSO
(cable providers) are not interested in the providing the multimedia
aspects of H.323 or SIP; there service objective to leverage VoIP as an
alternative to providing PSTN-like services using the customers existing
PSTN analog phones. This is the "thin client" model and some of these have
also defined the "rich client" model that would then use H.323 or SIP to
control PCs and enhanced multimedia phones. SIP and H.323 are already
standards for these applications and migrating the MEGACO charter to align
IETF, ITU-T SG16, and ETSI TIPHON so that the MGC-MG protocol is identical,
while a noble goal, may do an injustice to the original goal of producing a
"thin client" functionality needed, both for scalability and cost issues.
Both residential (be they cable modems or xDSL modem) and very large
trunking gateways (a needed network element that is essentially impossible
in an H.323 or SIP model), require a thin-client approach.

Limited focus was clearly demonstrated by the MGCP proponents and the flows
provided good indication of the VoIP features (but none multimedia
features)  that can be provided. Clearly, the MGC could have H.323 and SIP
proxy capability when the deployed network requires it, but the MGC-MG
protocol need not have to carry this baggage. For example, I'm not a
believer that H.245 (and I assume  H.235 for security, etc., etc.) should
ALWAYS be in the MG. I'm not saying the final MGC-MG has to be MGCP, but I
do think the protocol should not call up other protocols that require more
complexity (e.g., H.323 IPR stack issues, etc.) and it should be optimized
to the thin-client model.

I thought the purpose of this protocol was to allow for carrier-class
scalability to trunking and residential gateways requiring the equivalent
of PSTN POTS in a VoIP environment. I think at least some of the network
service providers would like to see gateways that eventually pass the
24-500 line range limits we are achieving with the H.323 model, not to
mention getting the cost per port down to reasonable levels............"

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From: "Callaghan, Robert" <[email-masked]>
Date: Wed, 31 Mar 1999 07:44:37 -0800

Sailaja,

If, as you say, it is the desire of some providers to supply an alternative
to PSTN services, then how does the Megaco proposal cover the multimedia
capabilities provided by PSTN using H.320 or H.324?

Bob

------------------------------------------------------------------
Robert Callaghan
Siemens Information & Communication Networks
Tel: +1.561.997.3756	Fax: +1.561.997.3403
Email:	[email-masked]
------------------------------------------------------------------

-----Original Message-----
From: [email-masked]
[mailto:[email-masked]]
Sent: Wednesday, March 31, 1999 10:15 AM
To: Douglas Clowes
Cc: Stephen Sprunk; [email-masked]; list iptel
Subject: Re: question about H.323/SIP and MDCP/MGCP

Hanlin,

This was part of a message Tim Miller sent over megaco mailing lists. I
think
his mail gives reasonal insight into/concerns about SIP/H323 Vs MDCP/MGCP
issues. In adition to to the explanations from Douglas and Stephen this will
give a big picture of where SIP/H323 and MDCP/MGCP fit into VOIP...

---------

---------

---

From: [email-masked]
Date: Wed, 31 Mar 1999 14:47:55 -0600

Robert,
Miller's message captures some of the ideas and concerns about
MGCP/MDCP/H323/SIP protocol placement in VOIP/Multimedia.As he said, MGCP's
origination was based on thin client model that will support carrier class load.
H323/320/324 proxies can be accommodated along with the new protocol (
megaco/MGCP) at MG level or MGC level  if multimedia functionality is necessary.
That does not mean that megaco protocol  has to have multimedia capability.
I guess, to implement SIP/H323 on MG or MGC should be decided by the vendor. If
the requirement is to have plain vanilla VOIP features, there is  not much use
of developing an elixir protocol.
But I believe there is some work going on to have multimedia features
implemented in megaco. H320 means having audio/video/T 120 data on the same
channel. So typically we end up with multiple media streams for the same
call/user.  So the MG and MGC will end up having 3 different contexts (depends
on the design ) or just one single context for all the streams. If I am right,
these issues are not solved yet. But I hope will be addressed  soon.

"Callaghan, Robert" <[email-masked]> on 03/31/99 09:44:37 AM

To:   Sailaja Talagadadeevi/MW/US/3Com, Douglas Clowes <[email-masked]>
cc:   Stephen Sprunk <[email-masked]>, Hanlin Fang/HQ/3Com, list iptel
      <[email-masked]>
Subject:  RE: question about H.323/SIP and MDCP/MGCP

Sailaja,

Bob

-----Original Message-----

Hanlin,

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