Introduces the session initiation protocol (SIP), which is a new signaling protocol developed to set up, modify, and tear down multimedia sessions over the Internet. Johnston, a former engineer at WorldCom, defines the types of clients and servers in a SIP network, and describes the function of request messages, response messages, and SIP headers. The second edition adds a chapter on SIP mobility and wireless multimedia communications.Copyright (C) 2004 Book News, Inc., Portland, OR