Networks can be interconnected by different devices in the physical layer networks can be connected by (1) or hubs. Which just move the bits from one network to an identical network. One layer up we find bridges and switches which operate at data link layer. They can accept (2) examine the MAC address and forward the frames to a different network while doing minor protocol translation in the process in me network layer, we have routers that can connect two networks, If two networks have (3) network layer, the router may be able to translate between the packer formats. In the transport layer we find transport gateway, which can interface between two transport connections Finally, in the application layer, application gateways translate message (4) . As an example, gateways between Internet e-mail and X.400 e-mail must (5) the e-mail message and change various header fields.
A. special
B. dependent
C. similar
D. dissimilar
In the following essay, each blank has four choices. Choose the most suitable one from the four choices and write down in the answer sheet. The key to SNMP (76) is its simplicity. It has a small command set that does a good job of collecting information from (77) any network device. In a SNMP environment, (78) of the work is handled by the network management system. Devices that are being managed are not (79) with processing (80) that might affect their performance.
A. many
B. almost
C. a lot of
D. nearly
[A] Why is foreign text "rendered meaningless" when passed through an on-line translation tool According to Sabine Reul, who runs a Frankfurt-based translation company, translation tools have limited uses, and problems arise when web users expect too much from them. "A translation tool works for some things," says Reul, "Say a British company wants to order a box of screws from a German supplier. A sentence like ’We need one box of a certain type of screw’ is something that a machine could translate reasonably accurately--though primitively."[B] Yet when it comes to translating blocks of text—words and sentences that convey thoughts and sentiments, on-line tools are bound to fail, she adds. "Beyond simple sentences, the on-line process simply doesn’t work because machines don’t understand grammar and semantics, never mind idiom and style." "Language is not a system of signs in the mechanical sense of the word", says Reul, "It is a living medium that is used to convey thought. And that is where machines fail. Human input is indispensable as long as computers cannot think." Reul and other translators look forward to the day when clever computers might help to ease their workload--but that time has not arrived yet.[C] Earlier this month the small German town of Homberg-an-der-Efze, north of Frankfurt, had to pulp an entire print run of its English language tourism brochure after officials used an Internet translating tool to translate the German text. According to one report, the brochure was "rendered meaningless" by the on line tool. Martin Wagner, mayor of Homherg-an-der-Efze, admits that the town made a "blunder". As a result of officials trying to save money by getting the Internet to do a translator’s job, a total of 7,500 brochures had to be binned.[D] "It would be nice if computers could do the job. And certainly the quest for machine translation has prompted a lot of linguistic research that may prove valuable in unforeseen ways. But experience to date confirms that even the most subtle computer program doesn’t think and you need to be able to think in order to translate."[E] This story highlights some of the pitfalls of translating on line. There are many instant translation tools on the web, but they are best used for individual words and short phrases, rather than for brochures, books or anything complex. For example, one of the joys of the web is that it grants you access to an array of foreign news sources. Yet if you were to use a translation tool to try to make sense of such reports, you could end up with a rather skewed and surreal view of the world.[F] Until the dawn of thinking computers, on-line translation tools are best reserved for words, basic sentences and useful holiday phrase. For tourism brochures, newspaper reports and the rest, you will have to rely on some old fashioned "human input".[G] Relying on on-line translation tools can be a risky business, especially if you expect too much of it. For the time being, might translation be something best left to the humansOrder: 44