英語翻譯
1.The goal is to make all programs,equipment,and especially data available to anyone on the network without regard to the physical location of the resource and the user.
2.A packet is transmitted to a subset of the machines.
3.owned and operated by a telephone company or Internet service provider
4.consists of two distinct components:transmission lines and switching elements
5.switching elements are specialized computers that connect three or more transmission lines.When data arrive on an incoming line,the switching element must choose an outgoing line to forward them.
6.In this case,the packet is received at each intermediate router in its entirety ,stored there until the required output line is free,and then forwarded.
7.The entities comprising the corresponding layers on different machines are called peers（including processes,hardware,or even human beings）
8.Each layer passes data and control information to the layer immediately below it,until the lowest layer is reached.
9.Routing or routeing is the process of selecting paths in a network along which to send network traffic.
10.The layer boundaries should be chosen to minimize the information flow across the interfaces.