OCN (オーシーエヌ), 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 Mbit/s and fiber up to 200 Mbit/s(download)100Mbit/s (upload) for ¥3,600-¥5,600 (US$$35 ~ $55) per month, with connections to large apartment buildings being less expensive than those to individual houses and small apartments. Note that as a result of regulations intended to promote competition, OCN themselves offer only internet service (routing), the physical line can be offered by NTT (the parent corporation), or by another company. (Likewise, one can lease a"Flets" fiber line and use Sony, Nifty, or another internet provider). Speeds up to 1Gbit/s are offered in Western Japan, while in East Japan only 200Mbit/s is officially offered for residential use, even though the underlying fiber infrastructure is capable of 1Gbit/s. OCN also offers an MVNO mobile broadband service called "OCN Mobile One", based on NTT Docomo's LTE infrastructure, but with data only SIM cards issued by OCN. Cards with and without SMS access are available. (In a tie-up with NTT Communications, one can install the "050+" application and use voice over IP so that the data only SIM cards can be used for voice as well.)