Christian;
Do you intend to replace H.323 ?
Definitely not. Just look at the picture above, which shows the relaying of
a call
between an SGCP controlled gateway and an H.323 agent. The combination of
gateways plus call agent forms a distributed H.323 system, which is
perfectly conforming to the H.323 standard...
If not H.323, why not SIP, then?
In fact, when we realized that we could not use H.323 between the call agent
and the gateways, we tried to base the design of SGCP on SIP. But we
stumbled on the fact that SIP is a peer to peer protocol, while we needed a
master slave protocol. However, interworking between SIP and SGCP is very
easy...
Technical comparisons are irrelevant.
For VoIP over telephony networks (that is, mostly over non-Internet
networks), H.323 and SS7 are the protocols to choose, because they
are defined by ITU-T.
As I pointed it out with regard to iMODE and WAP, an attempt to promote
protocols like SIP, a NAT friendly protocol even more complex than
H.323, was based on a wrong strategy destroying the Internet into a
collection of mostly-non-IP networks connected by application/transport
gateways with mostly-non-IETF application/transport protocols.
For IETF (IETF is for Internet not IP) style VoIP, that is, Internet
telephony, SGCP, MGCP, H.323 and SIP are all wrong that it is a waste
of mailing list bandwidth to compare them.
This mail of mine is not an exception, unless I make the following
advertisement:
If you are interested in Internet telephony, see you at
INET'2000 in Yokohama for the presentation of our paper
"The Simple Internet Phone".
;-)
Masataka Ohta