This is a thorough revision of the author's successful tcpip book with significant additional coverage of ipng (the next generation internet protocol), important clientserver applications such as the world wide web, critical security issues that relate to each protocol layer and application and material on domain name servers (how to install and use them). The revision will continue to have as its aim to provide practical, technically correct, information needed to plan for, use, operate, and maintain a tcpip network and its associated services.