HENRY SINNREICH is a Distinguished Technical Member of Engineeringat WorldCom and has worked on telephony systems, fiber optics, dataservices, and Internet services. He is an active member of IEEE,ACM, and the Internet Society, where he contributes to Internetstandards efforts within the IETF(Internet Engineering TaskForce).
ALAN B. JOHNSTON is also a Distinguished Technical Member ofEngineering at WorldCom and an Adjunct Professor of ElectricalEngineering at Washington University in St. Louis. As an activeparticipant in the IETF , he has coauthored and edited several SIPdrafts specifications. He is also the author of a previous bookabout SIP.