Section: 19.7.3 External Group Identifier
Content: An External Group Identifier identifies a group made up of one or more subscriptions associated to a group of IMSIs. The External Group Identifier shall have the form groupname@realm as specified in clause 2.1 of IETF RFC 4282 [53]. The groupname part format of the External Group Identifier shall contain a Local Identifier as specified in 3GPP TS 23.682[ Architecture enhancements to facilitate communications with packet data networks and applications ]  [98]. The realm part format of the External Group Identifier shall contain a Domain Identifier as specified in 3GPP TS 23.682[ Architecture enhancements to facilitate communications with packet data networks and applications ]  [98]. As specified in clause 4 of IETF RFC 4282 [53], the Domain Identifier shall be a duly registered Internet domain name. The combination of Local Identifier and Domain Identifier makes the External Group Identifier globally unique. The result of the External Group Identifier form is: "<Local Identifier>@<Domain Identifier>" An example of an External Group Identifier is: Local Identifier in use: "Group1"; Domain Identifier = "domain.com"; Which gives the External Group Identifier as: Group1@domain.com