Open Computer Network
OCN, or Open Computer Network, is the largest Japanese Internet [service provider], with over 7 million subscribers. It is owned by NTT Communications Corp, one of the largest telecommunication companies in the world. It offers dial-up and ISDN, DSL up to 50 Mb/s and fiber up to 200 Mbit/s download and 100 Mb/s upload.
As a result of regulations intended to promote competition, OCN themselves offer only internet service ; the physical line can be offered by NTT, or by another company. Speeds up to 1 Gb/s are offered in Western Japan, while in East Japan only 200 Mb/s is officially offered for residential use, even though the underlying fiber infrastructure is capable of 1 Gb/s.
OCN also offers an MVNO mobile broadband service called "OCN Mobile One", based on NTT Docomo's LTE infrastructure. Initially it started out as a data-only service, but more recently OCN Mobile One also offers an onseikake SIM card that provides full service without requiring any calling app.