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634 INTRODUCTION TO PACKET NETWORKS AND VoIPFigure 20.1-1 Local Area Network—common bus and packet switch.Historically, LAN and WAN equipment supplied by different manufacturers usedproprietary hardware and software. That made the interconnection of data networksfrom different suppliers difficult if not impossible. The introduction of standardnetwork interfaces and protocols such as Ethernet [3], ATM, and TCP/IP madeinterconnections possible on a worldwide basis.Internet. A packet network often needs to be connected to other packet networks inorder to access a wider pool of resources. That connection requires special provisions,either because of incompatible technologies or because of separate administrativedomains. Multiple individual networks connected to each other form aninternetwork or an internet (with a lowercase i). The Internet (with an uppercase I)is the best-known example of an internet and consists of the interconnection of avast number of packet networks on a worldwide basis, using the TCP/IP protocolsuite for communication. The World Wide Web (WWW) is a subset of the Internet,consisting of servers that use the HTTP protocol [4]. An internet appears to a host asFigure 20.1-2 Wide Area Network.