Using the International Mobile station Equipment Identity(IMEI)URN as an Instance ID
This specification defines how the Uniform Resource Name namespace reserved for the GSMA (GSM Association) identities and its sub- namespace for the IMEI (International Mobile station Equipment Identity) can be used as an instance-id as specified in RFC 5626 [1] and also as used by RFC 5627 [2]. Its purpose is to fulfil the requirements in RFC 5626 [1] that state "If a URN scheme other than UUID is used, the UA MUST only use URNs for which an RFC (from the IETF stream) defines how the specific URN needs to be constructed and used in the "+sip.instance" Contact header field parameter for outbound behavior."