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  3. Keeping the Net Secure On September 11 traditional telephone providers did a heroic job of struggling to restore service. Wh

Keeping the Net Secure On September 11 traditional telephone providers did a heroic job of struggling to restore service. Wh

admin2013-06-02  33
问题                                       Keeping the Net Secure
    On September 11 traditional telephone providers did a heroic job of struggling to restore 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 carders 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 exist.
    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 some 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&T’s long-distance volume jumped from a weekday average of about 300 million domestic voice calls to more than 431 million on September 11, the busiest weekday ever across AT&T’s domestic voice network.
    But despite the efforts to keep them in operation, under the extraordinary pressure of September 11 the traditional voice-telecommunications systems in the New York area and the Washington, D.C. area--both wire and wireless--were significantly overtaxed. In East Coast cities cell-phone networks could not keep up with demand. Many long-distance calls inbound to New York City were blocked, in part to reserve circuits for outgoing calls. On that day the Internet proved its value as an essential part of the modem communications system.
    More than half of America now uses the Internet. Globally, users number more than 300 million. Virtually all large businesses use the public Internet or private versions of the same technology to conduct their most important activities. So it was not surprising--although it was staggering--to see that on September 11 more than 1.2 billion instant messages were sent by AOL users alone. Slipping past the congested voice networks onto the PC screens of friends and family around the globe were the ties that bind us in the modem world:  "R U OK?" "ALRIGHT? “ “U THERE?"
    As voice networks blocked incoming calls to New York in order to relieve congestion, some carders pushed their voice traffic over the Internet. ITXC, which specializes in Internet voice services, saw its domestic wholesale business double on September 11 as carriers searched for new channels of communication; Yahoo’s PC to Phone calling service increased by 59 percent. The performance of these 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 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 many circuits are requested at one time, the system blocks calls.
   In contrast, Internet messages don’t 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 interconnected 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 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 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’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 triumph of libertarian visions, and the dawning of a new age of spontaneous self-organization. In the long run the Net’s 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 world’s citizens, 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, communications 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 make 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 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 traditional 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 order 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 high 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 Internet’s defenses need to be strengthened. The networks that compose its backbone should be encouraged with strong incentives to develop redundant interconnection points and diverse paths. The Internet’s 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 collections 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 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. These systems should be backed up by microwave and satellite-transmission systems.
    The terrorists did not directly target our communications networks, but those networks are an integral part of the democratic capitalism that they did attack. And we can use those networks to help fight back.
The system blocks calls when ______.
选项
答案too many circuits are requested at one time
解析 文章第六段中提到当许多线路在同一时间被使用时，电话就会被阻止。
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