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

From: [email-masked]
Date: Wed, 24 Mar 1999 15:17:14 -0800

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

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This message came from the IETF IPTEL Working Group Mailing List.

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From: "Dean Willis" <[email-masked]>
Date: Thu, 25 Mar 1999 00:42:22 -0600

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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