A study of Internet instant messaging and chat protocols

Instant messaging (IM) and network chat communication have seen an enormous rise in popularity over the last several years. However, since many of these systems are proprietary, little has been described about the network technology behind them. This analysis helps bridge this gap by providing an overview of the available features, functions, system architectures, and protocol specifications of the three most popular network IM protocols: AOL Instant Messenger, Yahoo! Messenger, and Microsoft Messenger. We describe common features across these systems and highlight distinctions between them. Where possible, we discuss the advantages and disadvantages of different technical approaches used in these systems to support different features and functions. We also briefly discuss ongoing efforts to standardize IM and chat-based protocols in IETF and other standards bodies.