me and go over a few years. With cable TV and phone com- panies competing to build the national Information Superhighway, no sin- gle standard can govern nationwide or worldwide communications. The original design of TCP/IP fits nicely within the current technological uncertainty. TCP/IP data can be sent across a LAN, can be carried within an internal corporate SNA network, or can piggyback on the cable TV. Further- more, machines connected to any of these networks can communicate to any other network through gateways supplied by the network vendor. Several other protocols are used with TCP/IP. These are usually bundled together into the TCP/IP protocol suite. These other protocols include the following: User Datagram Protocol (UDP) The UDP is used with applications that do not need to sequence datagrams. UDP does not perform as many checks and balances on the data as TCP does. It does not keep track of what is sent segment the data like TCP. Internet Control Message Protocol (ICMP) The ICMP is used for error messages and other messages intended for TCP/IP software itself, rather than any particular user program. ICMP is similar to UDP. It fits all its information into a single datagram and therefore does not have to break it down into many datagrams. ICMP works at the same layer as IP. The major reason for TCP/IP's success is that it can be ported across mul- tiple platforms. Whereas other protocol stacks are typically used in a LAN or a WAN environment, TCP/IP works on all aspects of the internetwork. A typical network may involve the integration of the following: Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright© 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. X.25, Internets, Intranets, and Extranets X.25, Internets, Intranets, and Extranets The LAN operating on a Token Ring or an Ethernet. The LAN OS may be Novell, Windows 95, Windows NT, or other. The Campus Area Network using Fiber-Dis