Using the International Mobile station Equipment Identity (IMEI) Uniform Resource Name (URN) as an Instance ID
This specification specifies how the Uniform Resource Name (URN) 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. Its purpose is to fulfil the requirements for defining how a specific URN needs to be constructed and used in the "+sip.instance" Contact header field parameter for outbound behavior.