NTT IP Phone Outage
An article in Saturday's Daily Yomiuri, which apparently isn't online, discusses outages in NTT East's systems on September 19 & 20. About 800,000 lines of its "Hikari" (light) service were affected. The principle problem seems to have been in relay servers that move calls between the IP network and the POTS (plain old telephone service) phones. Apparently they received 35,000 complaints about the problem.
Monday was a holiday, and on Tuesday morning traffic was three times normal, according to NTT. A server handling calls coming in from the POTS network became overloaded, and traffic was apparently shifted to another server in Miyagi Prefecture, which was designed to handle 200,000 calls but was given 260,000 calls. Controls had to be activated to limit traffic. The article doesn't say what those "controls" are, but presumably callers get a busy signal or perhaps a message, instead of being connected.
"To prevent the trouble recurring, NTT East on Thursday limited traffic between Hikari telephones and fixed-line phones and between Hikari phones and cell phones by 50 percent." Again, not a lot of details on how this accomplished.
NTT East says about 60 percent of new subscribers to its B-FLETS fiber optic Internet service also subscribe to its IP phone service. There are about 12 million IP phones in the country as of June, up 30 percent from a year ago.
There don't seem to have been any problems between Hikari phones and other Hikari phones. I'm curious about IP phones from other providers besides NTT East; if I had to guess, I would guess that the peering there is done on the POTS network rather than direct IP telephony connections.
The article includes various expressions of regret and government suggestions of more regulations, but no specific timetable for fixing the underlying problem.