Chapter 8The Internet 8.1.2 THE INTERNET: KEY TECHNOLOGY CONCEPTS However, these"dedicated"circuit-switching techniques were expensive and wasted available communications capacity-the circuit would be maintained regardless of whether any data was being sent. For nearly 70% of the time, a dedicated voice circuit is not being fully used because of pauses between words and delays in assembling the circuit segments, both of which increased the length of time required to find and connect circuits. a better technology was needed. 然而,这些“专用的”线路交换技术既价格昂贵又浪费有效的通信能力一 不论是否有数据输送都需要维持线路。由于字间的停顿和组装时的延迟 一条专用的声音线路在几乎70%的时间内没有得到充分利用,而这两种因 素都增加寻找和连接线路所需的时间长度。因此需要一种比较好的技术。 8-16
Chapter 8 The Internet 计算机专业英语 8-16 However, these “dedicated” circuit-switching techniques were expensive and wasted available communications capacity—the circuit would be maintained regardless of whether any data was being sent. For nearly 70% of the time, a dedicated voice circuit is not being fully used because of pauses between words and delays in assembling the circuit segments, both of which increased the length of time required to find and connect circuits. A better technology was needed. 然而，这些“专用的”线路交换技术既价格昂贵又浪费有效的通信能力— —不论是否有数据输送都需要维持线路。由于字间的停顿和组装时的延迟， 一条专用的声音线路在几乎70%的时间内没有得到充分利用，而这两种因 素都增加寻找和连接线路所需的时间长度。因此需要一种比较好的技术。 8.1.2 THE INTERNET: KEY TECHNOLOGY CONCEPTS
chapter 8 The Internet 8.1.2 THE INTERNET: KEY TECHNOLOGY CONCEPTS The first book on packet switching was written by Leonard Kleinrock in 1964, and the technique was further developed by others in the defense research labs of both the united states and England. with packet switching, the communications capacity of a network can be increased by a factor of 100 or more. The communications capacity of a digital network is measured in terms of bits per second. Imagine if the gas mileage of your car went from 15 miles per gallon to 1, 500 miles per gallon-all without changing too much of the car 第一本关于分组交换的著作是由 Leonard Kleinrock于1964年所著,美国 和英国防卫研究实验室的其他研究人员使这项技术得到进一步发展。由于 使用分组交换技术,网络的通信能力提高了100倍甚至更多。数字网络的 通信能力用每秒位来衡量。想象一下汽车行驶的里程,从每加仑汽油行驶 15里提高到每加仑汽油行驶1500里—而汽车没有太大的改变! 8-17
Chapter 8 The Internet 计算机专业英语 8-17 The first book on packet switching was written by Leonard Kleinrock in 1964, and the technique was further developed by others in the defense research labs of both the United States and England. With packet switching, the communications capacity of a network can be increased by a factor of 100 or more. The communications capacity of a digital network is measured in terms of bits per second. Imagine if the gas mileage of your car went from 15 miles per gallon to 1,500 miles per gallon—all without changing too much of the car! 第一本关于分组交换的著作是由Leonard Kleinrock于1964年所著，美国 和英国防卫研究实验室的其他研究人员使这项技术得到进一步发展。由于 使用分组交换技术，网络的通信能力提高了100倍甚至更多。数字网络的 通信能力用每秒位来衡量。想象一下汽车行驶的里程，从每加仑汽油行驶 15里提高到每加仑汽油行驶1500 里——而汽车没有太大的改变! 8.1.2 THE INTERNET: KEY TECHNOLOGY CONCEPTS
Chapter 8The Internet 8.1.2 THE INTERNET: KEY TECHNOLOGY CONCEPTS n packet-switched networks, messages are first broken down into packets Appended to each packet are digital codes that indicate a source address (the origination point)and a destination address, as well as sequencing information and error control information for the packet. Rather than being sent directly to the destination address, in a packet network, the packets travel from computer to computer until they reach their destination. These computers are called routers. Routers are special purpose computers that interconnect the thousands of different computer networks that make up the Internet and route packets along to their ultimate destination as they travel To ensure that packets take the best available path toward their destination, the routers use computer programs called routing algorithms 在分组交换的网络中,信息首先被分解为许多信息包。每个信息包附加数字代码用 于指示其源地址(开始点)和目的地地址、以及顺序信息和错误控制信息。在分组网 络中,信息包不是直接被送到目的地地址而是在计算机与计算机之间旅行直到它 们到达目的地。这些计算机叫做路由器。路由器是一种特殊用途的计算机,它将组 成因特网的成千上万个不同计算机网络互相联接起来,并在信息包旅行时将它们的 向终极目的地发送。路由器使用一种叫做路由算法的计算机程序,以确保信息包取 通向它们目的地的最佳可用路径。 开算机专业装语 8-18
Chapter 8 The Internet 计算机专业英语 8-18 In packet-switched networks, messages are first broken down into packets. Appended to each packet are digital codes that indicate a source address (the origination point) and a destination address, as well as sequencing information and error control information for the packet. Rather than being sent directly to the destination address, in a packet network, the packets travel from computer to computer until they reach their destination. These computers are called routers. Routers are special purpose computers that interconnect the thousands of different computer networks that make up the Internet and route packets along to their ultimate destination as they travel4. To ensure that packets take the best available path toward their destination, the routers use computer programs called routing algorithms. 在分组交换的网络中，信息首先被分解为许多信息包。每个信息包附加数字代码用 于指示其源地址(开始点)和目的地地址、以及顺序信息和错误控制信息。在分组网 络中，信息包不是直接被送到目的地地址,而是在计算机与计算机之间旅行直到它 们到达目的地。这些计算机叫做路由器。路由器是一种特殊用途的计算机，它将组 成因特网的成千上万个不同计算机网络互相联接起来，并在信息包旅行时将它们的 向终极目的地发送。路由器使用一种叫做路由算法的计算机程序，以确保信息包取 通向它们目的地的最佳可用路径。 8.1.2 THE INTERNET: KEY TECHNOLOGY CONCEPTS
chapter 8 The Internet 8.1.2 THE INTERNET: KEY TECHNOLOGY CONCEPTS Packet switching does not require a dedicated circuit but can make use of any spare capacity that is available on any of several hundred circuits. Packet switching makes nearly full use of almost all available communication lines and capacity. Moreover, if some lines are disabled or too busy, the packets can be sent on any available line that eventually leads to the destination point 分组交换不需要一个专用线路,但是可以利用几百条线路中任 线路和能力。而且,如果一些线路不通或太忙的话信息包能 在任何可用的、最终通向目的地的线路上传送 8 -19
Chapter 8 The Internet 计算机专业英语 8-19 Packet switching does not require a dedicated circuit but can make use of any spare capacity that is available on any of several hundred circuits. Packet switching makes nearly full use of almost all available communication lines and capacity. Moreover, if some lines are disabled or too busy, the packets can be sent on any available line that eventually leads to the destination point. 分组交换不需要一个专用线路，但是可以利用几百条线路中任 何可用的空闲能力。分组交换几乎充分利用了所有可用的通信 线路和能力。而且，如果一些线路不通或太忙的话,信息包能 在任何可用的、最终通向目的地的线路上传送。 8.1.2 THE INTERNET: KEY TECHNOLOGY CONCEPTS
Chapter 8The Internet 8.1.2 THE INTERNET: KEY TECHNOLOGY CONCEPTS TCP/IP. While packet switching was an enormous advance in communications capacity, there was no universally agreed upon method for breaking up digital messages into packets, routing them to the proper address, and then reassembling them into a coherent message. This was like having a system for producing stamps, but no postal system(a series of post offices and a set of addresses). TcPP。尽管分组交换是通信能力的一个巨大进步,但对于将 数字信息分解为信息包、将它们传输到适当的地址,然后重新 组装为原来的信息,还没有一种公认的方法。这就像有了一个 生产邮票的系统而没有邮政系统(一系列的邮局和一套住址)一 样 8
Chapter 8 The Internet 计算机专业英语 8-20 TCP/IP. While packet switching was an enormous advance in communications capacity, there was no universally agreed upon method for breaking up digital messages into packets, routing them to the proper address, and then reassembling them into a coherent message. This was like having a system for producing stamps, but no postal system (a series of post offices and a set of addresses). TCP/IP。尽管分组交换是通信能力的一个巨大进步,但对于将 数字信息分解为信息包、将它们传输到适当的地址, 然后重新 组装为原来的信息，还没有一种公认的方法。这就像有了一个 生产邮票的系统,而没有邮政系统(一系列的邮局和一套住址)一 样。 8.1.2 THE INTERNET: KEY TECHNOLOGY CONCEPTS