Section: 4.4 Regional Subscription Zone Identity (RSZI)
Content: A PLMN-specific regional subscription defines unambiguously for the entire PLMN the regions in which roaming is allowed. It consists of one or more regional subscription zones. The regional subscription zone is identified by a Regional Subscription Zone Identity (RSZI). A regional subscription zone identity is composed as shown in figure 7. Figure 7: Structure of Regional Subscription Zone Identity (RSZI) The elements of the regional subscription zone identity are: 1) the Country Code (CC) which identifies the country in which the PLMN is located; 2) the National Destination Code (NDC) which identifies the PLMN in that country; 3) the Zone Code (ZC) which identifies a regional subscription zone as a pattern of allowed and not allowed location areas uniquely within that PLMN. CC and NDC are those of an ITU-T E.164 VLR or SGSN number (see clause 5.1) of the PLMN; they are coded with a trailing filler, if required. ZC has fixed length of two octets and is coded in full hexadecimal representation. RSZIs, including the zone codes, are assigned by the VPLMN operator. The zone code is evaluated in the VLR or SGSN by information stored in the VLR or SGSN as a result of administrative action. If a zone code is received by a VLR or SGSN during updating by the HLR and this zone code is related to that VLR or SGSN, the VLR or SGSN shall be able to decide for all its MSC or SGSN areas and all its location areas whether they are allowed or not allowed. For details of assignment of RSZI and of ZC as subscriber data see 3GPP TS 23.008[ Organization of subscriber data ]  [2]. For selection of RSZI at location updating by comparison with the leading digits of the VLR or SGSN number and for transfer of ZC from the HLR to VLR and SGSN see 3GPP TS 29.002[ Mobile Application Part (MAP) specification ]  [31].