Section: 2.3 Allocation and assignment principles
Content: IMSI shall consist of decimal digits (0 through 9) only. The number of digits in IMSI shall not exceed 15. The allocation and assignment of Mobile Country Codes (MCCs) is administered by the ITU. The current assignment is available on ITU web site (https://www.itu.int/en/ITU-T/inr/Pages/default.aspx). The assignment of Mobile network Codes (MNC) is the responsibility of each national numbering plan administrator. MNCs under MCC ranges 90x are administered by the ITU. The MSIN is the third field of the IMSI, and is administered by the relevant MNC assignee to identify individual subscriptions. If more than one PLMN exists in a country, the same Mobile Network Code should not be assigned to more than one PLMN. The allocation of IMSIs should be such that not more than the digits MCC + MNC of the IMSI have to be analysed in a foreign PLMN for information transfer.