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1、KEYS TO EXERCISES Complete the sentences with the following words, changing the form if necessary.categorize allow significant flexible consist characterize integrate transmit1、A networked computing infrastructure can be categorized in many ways.2、Private Branch eXchange (PBX) technology allows for
2、a closed switched telephony network in a private environment (e.g. a business).3、Asymmetric Digital Subscriber Line (ADSL) uses paired modems and digital coding techniques to significantly increase the capacity of existing twisted copper pair telephone lines.4、Rate Adaptive DSL (RADSL) is a more fle
3、xible form of xDSL technology, which can adjust the transmission rates in 32 kbps steps, to better allocate bandwidth to user needs.5、Like the Internet model, DWDM has a layered structure consisting of a Transport layer and a Service layer.6、Computer LANs are characterized by their need for high-spe
4、ed interconnection between a set of co-located machines.7、Broadband ISDN (B-ISDN) is a standard for integrated networking of data, voice, and video at transmission speeds ranging from 34 Mbps to several Gbps (bandwidth on demand).8、Wireless connections are not only used to connect mobile equipment o
5、r local area networks, but are also increasingly employed in linking LANs to the Internet. Radio transmitters are used to create a directed link between LAN and ISP, obviating the need for cables in the access loop. Read the following passage and translate the underlined sentences into Chinese. The
6、source and destination are hosts identified by fixed length addresses: the IP address. An IP address is denoted as a series of 4 numbers with dots between them (for example: 195.169.17.146), where each number has a range of 0 through 255 (1 byte). In the IP header the IP address is stored as a 32-bi
7、t number, giving (theoretically) 232 possible addresses. The complete IP address consists of two parts. The first part, called network-id, identifies a network; the second part identifies an individual host within that network. To accommodate different sized networks, the complete 32-bit address spa
8、ce was divided into a number of ranges, called classes. For normal operation three classes were defined; Class A (0.x.x.x to 127.x.x.x), Class B (128.0.x.x to 191.255.x.x), and Class C (192.0.0.x to 223.255.255.x). Class D (224.x.x.x to 247.x.x.x) is meant for multicast (i.e., sending data to a grou
9、p of hosts), class E (248.x.x.x to 255.x.x.x) is reserved for experimental use. Class A can be used for very large networks, since the host part of a class A IP address is 24 bits wide. Class B has a 16-bit host part and class C an 8-bit host part. Some additional ranges within these classes are mea
10、nt for use on private Internets or intra-nets, and or not meant to be used outside these local nets. The fixed length network-ids did lead to a waste of address space since a lot of IP-addresses are unused. Combined with the explosive growth of the Internet over the last couple of years this has led
11、 to a shortage of IP addresses.1. The source and destination are hosts identified by fixed length addresses: the IP address.译文：消息源及其传输目的地是通过固定长度的地址(IP地址)识别的主机。2. In the IP header the IP address is stored as a 32-bit number, giving (theoretically) 232 possible addresses.译文：IP报头中的IP地址以32位二进制数的形式存储，理论上
12、提供了232个IP地址。3. The complete IP address consists of two parts. The first part, called network-id, identifies a network; the second part identifies an individual host within that network.译文：一个完整的IP地址包括两部分，第一部分是区分网络的网络号，第二部分区分某个网络中的单个主机。4. Class A can be used for very large networks, since the host par
13、t of a class A IP address is 24 bits wide.译文：由于类IP地址的主机地址宽度是24位，因此类地址适用于比较大型的网络。5. The fixed length network-ids did lead to a waste of address space since a lot of IP-addresses are unused.译文：由于固定长度的网络号使得大量IP地址未被使用，从而导致地址空间的浪费 Translate the following phrases into Chinese.1. convertinto (使)转而变为，转移2. r
14、oll out 铺开，碾平，滔滔不绝地讲出来，发出洪亮的声音，起床3. as well as 也，又，和一样4. be comparable to 与类似，与可比的5. be suited to 适合于的，与匹配的6. allow for考虑到，体谅，允许有，留出，给予7. out of doors 在户外8. on the basis of 基于，以为基础9. a variety of 多种的10. consist of 由组成11. be composed of 由组成12. at the expense of 以为代价13. launch oneself to 置身于14. far in
15、 the lead 遥遥领先15. be in operation 起作用，在工作，运转中 Translate the following sentences into English.、英特网设计者未能预见网络用户的急剧增长，最直接的表现就是注册IP地址的匮乏和路由选择列表容量的不足。Translation：The tremendous growth of the Internet was never anticipated by its designers, and is most directly felt in the shortage of registered IP-address
16、es and the size of routing tables.2、新版本IP协议出现的最重要的原因是人们需要一个更大的地址空间。Translation：The most important reason behind a new version of the IP protocol is the need for a larger address space.3、新地址结构的另外一个好处是支持了更多级的地址结构。Translation：Another benefit of the new address structure is that it allows for more levels of addressing hiera
