This Recommendation specifies the procedures and signalling protocol for the Message Waiting Indication supplementary service (SS-MWI) in H.323 (Packet Based Multimedia Communications Systems) networks.

SS-MWI is a supplementary service that enables a Served User A to be sent a Message Waiting Indication and also enables this Message Waiting Indication to be cancelled. The Served User may also be permitted to interrogate a Message Centre for any Message Waiting Indications.

The procedures and the signalling protocol of this Recommendation are derived from the Message Waiting Indication supplementary service as specified in ISO/IEC 15505 and ISO/IEC 15506.

This Recommendation makes use of the "Generic functional protocol for the support of supplementary services in H.323" as defined in Recommendation H.450.1.

This revision introduces a number of corrections and clarifications by incorporating technical and editorial corrections from the H.323-series Implementers Guide (03/2011) as well as some changes of editorial nature.