Section: 15.4 Home Network Realm
Content: The home network realm shall be in the form of an Internet domain name, e.g. operator.com, as specified in IETF RFC 1035 [19] and IETF RFC 1123 [20]. The home network realm consists of one or more labels. Each label shall consist of the alphabetic characters (A-Z and a-z), digits (0-9) and the hyphen (-) in accordance with IETF RFC 1035 [19]. Each label shall begin and end with either an alphabetic character or a digit in accordance with IETF RFC 1123 [20]. The case of alphabetic characters is not significant. During the MBMS service activation in roaming scenario, the BM-SC in the visited network shall derive the home network domain name from the IMSI as described in the following steps: 1. Take the first 5 or 6 digits, depending on whether a 2 or 3 digit MNC is used (see 3GPP TS 31.102[ Characteristics of the Universal Subscriber Identity Module (USIM) application ]  [27], 3GPP TS 51.011[ Specification of the Subscriber Identity Module - Mobile Equipment (SIM-ME) interface ]  [66]) and separate them into MCC and MNC; if the MNC is 2 digits then a zero shall be added at the beginning; 2. Use the MCC and MNC derived in step 1 to create the "mnc<MNC>.mcc<MCC>.3gppnetwork.org" realm name; 3. Add the label "mbms." to the beginning of the realm name. An example of a home realm used in the MBMS roaming case is: IMSI in use: 234150999999999; Where: MCC = 234; MNC = 15; MSIN = 0999999999 Which gives the home network realm: mbms.mnc015.mcc234.3gppnetwork.org.