http://www.rfc-editor.org/rfc/rfc5028.txt
RFC 5028: A Telephone Number Mapping (ENUM) Service Registration for Instant Messaging (IM) Services, R. Mahy2007-10-01T23:00:00-00:00This document registers a Telephone Number Mapping (ENUM) service for Instant Messaging (IM). Specifically, this document focuses on provisioning 'im:' URIs (Uniform Resource Identifiers) in ENUM. [STANDARDS-TRACK]