通信工程专业英语 Unit 14：Packet Switching

,Packet Switching,Specialized English for Communication Engineering,*,Specialized English for Communication Engineering,*,Specialized English for Communication Engineering,*,Specialized English for Communication Engineering,专 业 英 语,Specialized English,Unit 14,：,第二部分 通信技术,Packet Switching,NEW WORDS AND PHRASES,mainframe,n.,计,主机,arbitrary,adj.,任意的,quantize,vt,.,数,用基本数的倍数表示,quanta,n.,量,forward,vt,.,转发，转寄,topological,adj.,拓扑的,core,n.,（果实的）核,instantaneous,adj.,瞬间的,NEW WORDS AND PHRASES,methodology,n.,方法学,emulate,vt,.,仿真,reserve,vt,.,储备,TDM(Time,Division Multiplexing),时分复用,PSTN(Public,Switched Telephone Network),公众交换电话网,QoS(Quality,of Service),服务质量,VC(Virtual,Circuit),虚电路,If,circuit switching was used to support data communications,，,the dedicated resources for a connection,would be,idle most of the time- very inefficient use of band- width,本句是一个祈使句，,If.,主语,would be.,。,全句可译为：如果在数据通信中使用电路交换，那么在大部分时间里（电路交换）连接的专用资源将是空闲的,-,非常不经济的带宽使用。,TEXT,Since packet transmissions from different sources are not coordinated,，,multiple packets arriving simultaneously at the packet switch on different input ports can all be,destined to,the same output port,这是一个由,since,引导的复合句。,destined to,去往,的。,全句可译为：尽管不同来源的分组传输不同步，但是同时到达交换机不同端口的很多分组可能是去往同一个输出端口的。,In packet switching,，,it requires an explicit 1abel (destination address) on the header of each packet to associate it with its destination node,，,while the position of the packet in time does not correspond to any channel information,全句可译为：在分组交换中需要每个分组的头部有一个显示,(,明确的,),地址（目的地址）把分组和其目的节点联系起来，而分组在时间上的位置与任何信道信息并不对应。,Hence,，,connections in packet switched network are known as virtual connections or VCs,，,to distinguish,them from nailed up connections with dedicated resources in circuit switched networks,此句是一个简单句。,to distinguish,不定式短语用来表示,hence,后结果的原因。,全句可译为：为了和电路交换网中有专用资源的固定连接区别，因此，将分组交换网中的连接命名为虚连接或,VC,。,