Section: 9.1.1 Format of APN Network Identifier
Content: The APN Network Identifier shall contain at least one label and shall have, after encoding as defined in clause 9.1 above, a maximum length of 63 octets. An APN Network Identifier shall not start with any of the strings "rac", "lac", "sgsn" or "rnc", and it shall not end in ".gprs", i.e. the last label of the APN Network Identifier shall not be "gprs". Further, it shall not take the value "*". In order to guarantee uniqueness of APN Network Identifiers within or between GPRS/EPS PLMN, an APN Network Identifier containing more than one label shall correspond to an Internet domain name. This name should only be allocated by the PLMN if that PLMN belongs to an organisation which has officially reserved this name in the Internet domain. Other types of APN Network Identifiers are not guaranteed to be unique within or between GPRS/EPS PLMNs. An APN Network Identifier may be used to access a service associated with a GGSN/PGW. This may be achieved by defining: - an APN which corresponds to a FQDN of a GGSN/PGW, and which is locally interpreted by the GGSN/PGW as a request for a specific service, or - an APN Network Identifier consisting of 3 or more labels and starting with a Reserved Service Label, or an APN Network Identifier consisting of a Reserved Service Label alone, which indicates a GGSN/PGW by the nature of the requested service. Reserved Service Labels and the corresponding services they stand for shall be agreed between operators who have GPRS/EPS roaming agreements.