试题出自试卷《中国艺术研究院2009年考博英语真题》

Nobody would expect a city water system designed for 1 m residents to be able to handle a 1,000-fold increase in population in just a few years. Yet that is what the internet’s fundamental addressing scheme has had to accommodate. When the network was first established there were only a handful of computer centres in America. Instead of choosing a numbering system that could support a few thousand or million addresses, the internet’s designers foresightedly opted for one that could handle 4 billion. But now even that is not enough.
The addressing system, called internet protocol version 4 (IPv4), cannot keep up with the flood of computers, mobile phones, hand-held gadgets, games consoles and even cars and refrigerators flooding onto the network. Nearly 85% of available addresses are already in use; if this trend continues they will run out by 2011, the Organisation for Economic Cooperation and Development, a think-tank for rich countries, warned in May.
The shortage is not the only problem; so too is growing complexity. IPv4 addresses are allocated in blocks to network operators. The path to reach each network is published on a global list that is constantly updated. Big computers, called routers, use these entries to guide the flow of traffic across the internet. But as more devices and networks link to the internet, it becomes necessary to subdivide the address blocks into ever-smaller units. This risks overtaxing the millions of routers that handle the internet’s traffic, which must be regularly upgraded to keep up. Were there no alternative to IPv4, parts of the internet would eventually suffer from sporadic outages.
Fortunately a new system does exist, called internet protocol version 6, which provides 3.4x1038 addresses. This means IPv6 addresses can be allocated to network operators and companies in much larger quantities. It also provides a clean slate for establishing new paths over the internet, reducing complexity. But switching means upgrading millions of devices.
In fact, support for IPv6 is already widely available in software and hardware, but it has not been used much. Only a few research institutions and the American government took the IPv6 plunge early on. (In America all federal agencies must be capable of using IPv6 by June 30th 2008, by executive order.)
But in recent months the pace of change has picked up. In February Mr. Vixie, a network engineer, flipped a switch that means domain names can now map onto IPv6 addresses. This may herald more widespread adoption of the new protocol, since it means that any organisation can use IPv6 addresses with its domain names, and users can access them without special rigging.
1. From the first paragraph we may infer that the design of the internet’s fundamental addressing scheme is ____.
2. According to the author, the addressing system IPv4 ____.
3. The potential problem with internet protocol version 4 today is that ____.
4. It is implied that IPv6 addresses ____.
5. Which of the following may serve as the best title of the passage?