新计算机专业英语 教学课件 霍宏涛 Chapter7.pptVIP

在线教务辅导网： 教材其余课件及动画素材请查阅在线教务辅导网 QQ:349134187 或者直接输入下面地址： Professional English in Computer Field Chapter Seven Computer Network 内容 正文 Network Topology SLIDING WINDOW PROTOCOLS 阅读材料 IPv6 Router 7-1 Network Topology Network topologies are categorized into the following basic types: Bus topology Star topology Ring topology Tree topology Mesh topology Key Words topology n.拓扑结构 layout n.布局 hybrids n.合成物 ethernet n.以太网络 repeater n.中继器 token ring 令牌环 backbone network 骨干网络 protocol n.协议 Key Words coaxial adj.同轴的 fault tolerance 误差，错误范围（容许值） concentrator n.集线器 unshielded twisted pair 屏蔽双绞线 Notes A bus topology becomes slow by heavy network traffic with a lot of computer because networks do not coordinate with each other to reserve times to transmit. 当一个总线拓扑结构里有很多的计算机的时候，由于网络无法协调每个计算机以保留传输时间，严重的网络拥塞会导致总线速度变慢。 One aspect of the Ethernet protocol requires that a signal sent out on the network cable reach every part of the network within a specified length of time. Each concentrator or repeater that a signal goes through adds a small amount of time. 以太网协议的一个方面要求一个发送到网络上的信号须在预定的时间内到达网络的每一个角落。信号经过的每个网络集线器或中继器都会增加一个小的延时。 7-2 SLIDING WINDOW PROTOCOLS Key Words data frame 数据帧 full-duplex 全双工 acknowledgement 确认 ack field 应答域 piggybacking 捎带传输 data link layer 数据链路层 Key Words outbound n. 输出 sequence number 序号 shut off 关闭 Notes When a data frame arrives, instead of immediately sending a separate control frame, the receiver restrains itself and waits until the network layer passes it the next packet. 当数据帧到达时，接收者并不立即发送一个独立的控制帧，而是保留直到网络层传来下一个包。 Notes Although these protocols give the data link layer more freedom about the ord-er in which it may send and receive frames, we have definitely not dropped the requirement that the protocol must deliver packets to the destination network layer in the same order they were passed to the data link layer on the sending machine. 尽管这些协议使