A conferencing system is defined by "A framework and Data Model for Centralized Conferencing" and represents a container for administering and managing all conference related information. The conference user concept is introduced in the framework to identify the entity participating in a conference and manipulating conferencing system related properties. This document defines a Conference User Identifier and provides some guidelines for identifying a specific conference user within a conferencing system. The document also provides some examples of the logical mapping of this conference user identifier to protocol and signaling interface specific user identifiers.