This study aims to examine the use cases and potential requirements that allow different Public User Identities of the form sip:user@domain belonging to the same domain to be:
assigned by multiple network operators, where an individual Public User Identity is served by only a single network operator for all IMS services;
provisioned by network operators in the case where other URI schemes have already been, or are going to be, provisioned by different service providers in the internet.
The Public User Identities could be SIP URIs associated with or derived from user identities of services from the Internet domain.
This study also aims to clarify the relationships (e.g., business, interworking) between the Domain Name Owner, the assignee of sip:user@domain where it is not the same as the domain owner, and operators sharing the domain name.
Any potential regulatory aspects will also be considered.