[SIP author here, for better or worse] SIP's victory over H.323 was definitely an odd story. Henning Schulzrinne wrote a draft called SCIP, which was essentia

[SIP author here, for better or worse] SIP's victory over H.323 was definitely an odd story. Henning Schulzrinne wrote a draft called SCIP, which was essentially HTTP for multimedia calling. SCIP overlapped with what Eve Schooler and I were already doing. We thought his version was too complicated (ha!), so I rushed out a draft based on what I had been coding in the MBone session directory sdr, which was a simpler UDP-based SIP. We presented them both at the same IETF meeting in 1997 where I was already standardizing SDP, and got general support from the room, but the main message we took home was there can be only one! So we met up at Columbia a month later and spent a day arguing out which features of the two protocols to keep. The resulting protocol is the basis of the SIP we know today. By this time, H.323 was gaining lots of momentum and Microsoft and Intel had adopted it. What chance for a few academics against Microsoft and Intel? But I was chairing the MMUSIC WG in the IETF and, quite simply, no-one told us to stop. So with the hubris of youth, we just carried on anyway. Loads of people told us we couldn't possibly win, but H.323 was just too ugly and telco-like, and (in the early versions) took so many round trip times to do anything at all, that we really didn't like it. Around this time it started to occur to some of the telcos that Internet traffic would before long exceed phone traffic, and it would then make no sense to run two networks. In particular Henry Sinnreich at Internet MCI started to look around for what they should do, and he thought SIP's proxy architecture would fit their needs better than H.323. As a result I went down to Dallas and gave a couple of days tutorial to all the Internet MCI folks about how we saw IP-based internet multimedia working out. After that, Internet MCI started to push SIP, and other telcos noticed. Increasingly it seemed our main allies were telcos. And so it turned out that in the early VoIP space, telcos held more sway than Microsoft and Intel. Eventually Microsoft moved to SIP too. The downside was that SIP rapidly accumulated lots of telco cruft, and the original peer-to-peer email-address-based nature of SIP wasn't what actually took off. So, H.323 came from bell-heads, but got backed by net-heads. SIP came from a few net-head academics, but got backed by bell-heads. In the end, for better or worse, the latter won. Ever since an IETF meeting around 2000 where there was more than 100 SIP-based internet drafts, I've regarded SIP as being my success disaster. It's a huge success, but it could have been so much simpler and cleaner.