This Supplement provides background, tutorial and guidance information on a broad range of operational and administrative issues associated with the inclusion of E.164 numbers into the DNS (i.e., the inclusion of ENUM domain names based on E.164 numbers). It contains considerations of and potential consequences arising from such issues. This Supplement does not attempt to provide solutions for these issues; such solutions are left to the prerogative of Administrations for whom a range of oversight responsibilities is proposed in this Supplement. This Supplement describes the various issues and provides some guidance considering various ways to address each issue. Please refer to the Recommendation(s) in which TSB processes and procedures relating to requests for delegations of domain names corresponding to E.164 country codes are specified.