This document specifies an application-level protocol (i.e., payload type) for chat tools using the Real Time Protocol for Distributed Interactive Media (RTP/I). RTP/I defines a standardized framing for the transmission of application data and provides protocol mechanisms that are universally needed for the class of distributed interactive media. A chat tool provides an instant messaging service among an arbitrary number of users. This documents specifies how to employ a chat tool with RTP/I and defines application data units (ADUs) for chat operations. This protocol definition allows standardized collaboration between different chat implementations.