The fault occurred on Tuesday afternoon in the TAT-14 fibre-optic cable system that connects the US, Denmark, Germany, the Netherlands, France and the UK, and is understood to have left TAT-14 unusable for traffic at present. TAT-14 is owned by a consortium of telcos. According to BT, a member of the consortium, the disruption occurred between France and the Netherlands and disrupted a range of telecommunication services.
"France Telecom will send a cable ship out to fix and repair the problem," said a BT spokesman, adding that the cause of the problem is not known. It's also not clear how long the fault will take to repair.
As TAT-14 is a dual, bi-directional ring of cable, a single serious fault should not be enough to break it, as traffic would still be able to flow between the countries on the ring. Unfortunately, a part of the cable near the US coast had already suffered a technical fault earlier this month, which meant there was no built-in redundancy to cope with Tuesday's failure. According to BT, the US-side fault should be fixed by the end of this week, which will bring the cable network online again.
Tuesday's failure affected BT's voice calls, rather than its data services, but it is understood that a number of Internet service providers experienced faults.
Vanessa Evans, of LINX, the London Internet Exchange, which carries nearly all UK Internet traffic and over half of Europe's Internet traffic, said she saw a drop in traffic of around two gigabits per second. At its peak, LINX sees 32 gigabits of data every second. She added that the Internet was not broken, as traffic was rerouted through other networks.
It's currently unclear whether the TAT-14 failure was responsible for problems experienced by Telewest late on Tuesday, when email and personal Web page services were unavailable. Telewest said its services were getting back to normal on Wednesday morning, but that it was still not sure what caused the outages. One theory it is exploring is that it suffered a denial of service attack.
It is understood that many other UK ISPs also suffered problems yesterday. NTL warned its customers that, due to a major server outage, ntl:home Internet customers on all packages may currently be experiencing problems with all Internet access, including Web browsing, email, ftp and newsgroups.
ZDNet UK's Rupert Goodwins contributed to this story.