One of Japan's biggest ISPs will soon begin imposing daily upload limits on its customers in response to a portion of its user base who upload massive amounts of data.

OCN, the carrier operated by NTT Communications, will introduce a daily upload limit of 30G bytes from Aug. 1. Customers that exceed the amount will first be asked to observe it, but those that repeatedly break it will have their access suspended, the carrier said Wednesday.

Downloads will continue to be unlimited.

By targeting large uploaders the limits will likely hit the small portion of OCN's 7 million customers who operate file-sharing servers from their connections, said Tei Gordon, an NTT spokesman in Tokyo. The limit corresponds to about 7 full-length movies per day.

NTT, like most Japanese ISPs, has enjoyed booming business from the fast spread of fiber optic Internet connections that provide links of 100Mbps to and from the Internet for around ¥5,000 ($46) per month.

In parallel with the explosion in broadband usage has come a need to continuously upgrade its core network to carry ever-increasing amounts of traffic that now include streaming IPTV services offered by the carriers themselves.

However, NTT said that despite the upgrades "a small number of individual users have been monopolizing substantial network resources by uploading massive amounts of data, which can slow the speed of the network and lower communication quality for other users."

The IDG News Service is a Network World affiliate.