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
