Siemens Enterprise Communications Microsoft Corporation Do Not Disturb (DND) is a commonly used expression for indicating a condition where a human user of real-time communications does not wish to be interrupted by incoming calls or other forms of communication. This document discusses the nature of DND, ways of observing DND, and limitations of and possible improvements to DND support in the Session Initiation Protocol (SIP) and the Rich Presence Information Data Format (RPID). This work is being discussed on the bliss@ietf.org mailing list.