大学六级-69及答案解析.doc
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1、大学六级-69 及答案解析(总分:693.00,做题时间:90 分钟)一、BPart Writing(总题数:1,分数:106.00)1.BLeisure time in a typical week: by sex and employment status, 19981999/B (分数:106.00)_二、BPart Reading (总题数:1,分数:70.00)BKeeping the Net Secure/BOn September 11 traditional telephone providers did a heroic job of struggling to restor
2、e service. When the World Trade Center towers fell, they severely damaged a Verizon central office with 350,000 voice lines and 3.5 million data circuits carrying the financial information that is the lifeblood of Wall Street firms. Verizon employees and those of many other telecommunications carder
3、s worked night and day, alongside the firemen, the police, and volunteers, at their own recovery job. In about a week they had rerouted some two million data circuits, restored switches, and installed temporary power supplies. The other 1.5 million circuits originated in buildings that no longer exi
4、st.In the days after the attack the number of voice calls in the five boroughs of New York City doubled, from the normal 115 million a day to more than 230 million. For the next six days Verizon waived charges for its pay phones in Manhattan. On a single day following the disaster residents placed s
5、ome 22,000 local calls free of charge from regular sidewalk pay phones below Canal Street, and Williams Communications switched five million voice calls in the metropolitan area-three times the average daily volume. AT Yahoos PC to Phone calling service increased by 59 percent. The performance of th
6、ese voice-over-IP services suggests that in only a handful of years most voice traffic is likely to be carded on the Internet.Why did the Internet work so well in the face of huge volume? Because its “distributed“ technology is inherently robust. “Normal“ phone connections, whether by means of wired
7、 line networks or by wireless cellular networks, open a specific circuit, or channel, connecting the person who is called and the caller. Just as if a superhighway lane were opened for one car only, the circuit remains dedicated to the conversation even if no one is speaking at the moment. If too ma
8、ny circuits are requested at one time, the system blocks calls.In contrast, Internet messages dont travel on designated circuits. Instead, the messages are coded in is and Os, and then disassembled into packets of data. The packets go out from the PC down the phone line and into the maze of intercon
9、nected fibers that envelops every metropolitan area of every developed country in the world. Like cars on a superhighway, packets share lanes on the Net.Each packet contains a destination address. As the packet moves into the maze, it encounters a router that selects the next step in the network. If
10、 the router senses congestion on one route, it selects another. The AOL instant-message packets could work their way around the jams and outage of the voice network and find their destinations in seconds.One lesson from September 11 is that in order to maintain an effective communications system in
11、the face of any calamity, we should promote and protect the Internet as a primary network, encouraging the private sector and using the resources of the public sector to make it faster, more robust, ubiquitous, and better integrated with other media. This policy would be consistent with the Internet
12、s original development as an aspect of national security.Not many creators of Internet technology or leaders of Internet companies have been seriously interested in world affairs. Indeed, only yesterday many people imagined, naively, that the rise of the medium meant the end of government, the trium
13、ph of libertarian visions, and the dawning of a new age of spontaneous self-organization. In the long run the Nets emphasis on liberty can be fused with the needs of a civil equitable, ordered state. But in the short run we need practical steps to help keep the Internet secure. The worlds citizens,
14、businesses, and governments should come together to take two actions.First, Internet access should be made truly global. In less developed countries this means expanding communications systems so that more people have exposure to and access to information from the outside world. Obviously, communica
15、tions technology does not by itself end conflict or convert nations to democracy. But it helps, and those goals are easier to reach with a modem communications system than without one. However our current war against terrorism ends, along the way the United States and its allies will undoubtedly mak
16、e a variety of economic promises to the Central Asian states whose support we need. It would be better to direct aid toward thought-out goals than to grant it slapdash. A $ 10 billion investment fund for communications improvements throughout the developing world, managed by an independent board and
17、 funded half by private institutions and half by governments, would be a wise use of our resources.In developed countries universal access means ensuring that businesses and citizens can all get high-speed connections to the Internet, much as they now have universal dial-tone access to the tradition
18、al telephone system. The United States has a long history of subsidizing the growth of a democratically available communications system. In keeping with the established universal service policy, business and suburban customers of telephone services are “overcharged“ some $ 30 billion each year in or
19、der to subsidize basic telephone rates for rural customers. Diverting $ 10 billion of this universal-service funding could eventually make broadband service available on a near universal basis. Consumers could draw on a federal fund for whichever competing service they chose. The fund would pay a hi
20、gh proportion of the total cost for poor and rural users, a low one or none at all for rich users. Andy Grove, the chairman of Intel, recently called for a similar investment plan.Second, the Internets defenses need to be strengthened. The networks that compose its backbone should be encouraged with
21、 strong incentives to develop redundant interconnection points and diverse paths. The Internets conceptual design makes it inherently resilient, but its physical structure and hardware need to be more secure than they are now. The one or two dozen essential crossroads of the Internet are basically c
22、ollections of computers in buildings. These are vital nodes of our national security, and they ought to be as carefully protected as our military installations. The Internet has a rising number of co-location facilities where many fiber cables are aggregated. If any of them goes down, traffic can be
23、 interrupted for long periods. This became clear last summer in Baltimore, when a train derailment damaged a substantial fiber link and affected the flow of Internet traffic around the globe.Every essential node should have a backup. Internet messages are now carried mainly on fiber-optic systems. T
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