Sadahiro Sato, GM of BB Phone Service Division of Softbank, gave a very informative presentation. You can find the backbone of Yahoo! BB in Japan and they have acquired Japan Telecom last year really for their backbone network across Japan.
And since Yahoo! BB has 22% of the telephony market share in Japan, nearly 33% of their revenue comes from voice termination from the other telco. (so they want to do well but not too much to kill off all their competitors :-)
The network protocol is a mixature of MGCP, H.323 and SIP but he talks about moving all to SIP eventually (yeah!). And watch out for Yahoo! BB offering WiFi phone services, particularly, he mentioned about a WiFi+CDMA phones. He also asked the audience to talk to their government to give Yahoo! a mobile license :-)
Some other interesting note: Yahoo! BB has 4.4M subscribers now and 95% of the Yahoo! BB subscribers took up BB Phone services. And yes, it is finally confirmed: Yahoo! BB TA (terminal adaptor) redirect all the emergency calls, toll-free calls, etc etc (ie, all the money losing calls) and fall back to the NTT. Haha, no wonder NTT is pissed!
ps: I am blogging this on stage.
