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

From: "Stephen Sprunk" <[email-masked]>
Date: Wed, 24 Mar 1999 17:55:44 -0600

MGCP/MDCP is (in theory) much simpler to implement, and therefore better
suited for mass-production dumb devices like desktop feature phones or
high-density media gateways; those dumb devices would then be controlled by
a intelligent SIP/H.323 device.  You could implement H.323 or SIP end-to-end
if you wished.

Stephen

     |          |         Stephen Sprunk, K5SSS, CCIE #3723
    :|:        :|:        NSA, Network Consulting Engineer
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-----Original Message-----
From: [email-masked] <[email-masked]>
To: list iptel <[email-masked]>
Date: Wednesday, March 24, 1999 17:23
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.

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

---

From: Douglas Clowes <[email-masked]>
Date: Mon, 29 Mar 1999 08:48:36 +1000

Hanlin,

This response is probably the closest one to date, but your request would
probably be better served on the "megaco" list, where the MGCP/MDCP people
hang out.

SIP and H.323 are overlapping standards at the call-control level, while
MGCP and MDCP are competing standards at the connection control level.

MxCP is targeted at operation _within_ a SIP/H.323 gateway, which is
decomposed into a controller and several media devices. It is possible for
MxCP to establish a media connection between two media devices and produce
what could be regarded as a call, if both media devices were under the
control of a _single_ controller.

To establish a connection between two media devices which were under the
control of _different_ controllers, an exchange of messages is required
between those controllers, to coordinate the connections - this is where
SIP and H.323 come in.

For a gateway that is not decomposed, MxCP is not required. Ideally, at the
SIP/H.323 level, it should not be required to know that MxCP is implemented
in a gateway. SIP and H.323 also operate with endpoints that are not gateways.

Hope this helps.

Douglas

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