Networks can be interconnected by different devices in the physical layer networks can be

第1题

The Internet is a （) system of interconnected computer networks that use the standard Inte

The Internet is a () system of interconnected computer networks that use the standard Internet protocol suits(TCP/IP) to serve several billion users worldwide。

A．global B．regional C．local D．national

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第2题

Multipurpose Internet Mail Extension （MIME)is a（76)document messaging standard in the Inte

Multipurpose Internet Mail Extension (MIME)is a(76)document messaging standard in the Internet environment. With MIME, users can send(77)E-mail messages that include audio, video, graphices, and text to any other user of a TCP/IP network. Richtext information can also be(78)into messages. It defines the fonts, formats, and(79)features of a document so the document can be easily(80)on many different types of systems.

A．complete

B．compound

C．simple

D．efficient

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第3题

Communication networks can be classified in terms of their physical arrangement or（73)Thre

Communication networks can be classified in terms of their physical arrangement or(73)Three common(73)are the star, bus, and ring.

A．structures

B．topologies

C．protocols

D．frames

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第4题

Two hundred years ago, it took several weeks for the news of the important Battle of T

rafalgar to reach London.Nowadays, you can watch a terrorist attack as it happens anywhere in the world.The communications revolution means that we are constantly bombarded with instant news.This has great advantages, but it also raises important questions.

Satellites have enabled immediate reporting worldwide.A reporter can send the news to a network like CBS News and within seconds it can be all over the world.They send electronic reports that go straight into the newspaper or onto the TV screen.Reporters can now also transmit images through their mobile phones.Consequently, live, “on-the-spot” reporting has become the norm and TV viewers can get a much better idea of what a natural disaster, a conflict or an interesting scientific discovery is like.

In recent years, several changes have occurred in the ownership of news media.Networks owned by large companies and governments have become bigger and very powerful.These networks – such as BBC News 24–are hungry for news and have huge audiences.However, there can only be a limited number of such networks and their ownership is a big issue.

Some companies not only own TV and radio networks but newspaper groups as well.Who decides what news to publish and what sort of “spin” to put on it？ Is it always objective？ There are now “spin doctors” who manipulate the news,emphasising certain parts and not others – and as a result, much of it is not neutral.Therefore, the question of control of the media matters very much.In some cases, the media companies are more powerful than governments.They can even influence elections.So the question is – should they be controlled and if so, by whom？

1.Immediate reporting has become possible all over the world because of().

A.reporters

B.the use of news networks

C.the use of satellites

D.the communications revolution

2.()has become the norm.

A.Electronic reports

B.Instant news

C.Live reporting

D.Transmitting images through mobile phones

3.In what ways are media companies powerful？ ()

A.They can influence elections in some way

B.Nowadays, the manipulation of news reports is possible

C.They not only own TV and radio networks but newspaper groups as well

D.All of the above

4.According to the passage, the big issue is ().

A.ownership of news networks

B.that there can only be a limited number of such networks like BBC News 24

C.that networks owned by large companies and governments have become bigger and very powerful

D.that the news reporting is manipulated by big companies

5.What can be inferred from this passage？ ().

A.The disadvantages of the communications revolution outweigh its advantages

B.We should put the question of control of the media on the agenda

C.The news reporting has always been objective

D.A reporter can send news directly to the audiences all over the world

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第5题

Networks can be interconnected by different devices. In the physical layer, networks can b

e connected by(66)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(67), examine the MAC address, and forward the frames to a different network while doing minor protocol translation in the process. In the network layer, we have routers that can connect two networks. If two networks have(68)network layer, the router may be able to translate between the packet formats. In the transport layer we fmd transport gateway, which can interface between two transport connections. Finally, in the application layer, application gateways translate message(69). As an example, gateways between Internet e-mail and X.400 e-mail must(70)the e-mail message and change various header fields.

A．repeaters

B．relays

C．connectors

D．modems

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第6题

Packet switching is a method of slicing（71) messages into parcels called "packets," sendin

Packet switching is a method of slicing(71) messages into parcels called "packets," sending the packets along different communication(72) as they become available, and then reassembling the packets(73) they arrive at their destination. Prior to the development of packet switching, early computer networks used leased, dedicated telephone circuits to(74) with terminals and other computers. In circuit-switched networks such as the telephone system, a complete point-to-point(75) is put together, and then communication can proceed.

A．binary

B．useful

C．digital

D．analog

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第7题

Astute service providers realize that the continued support of legacy X.25 and asynchronou

s network elements using separate operations networks is cost(71). For example, the maintenance of multiple networks can require additional staff. Often, this staff must be trained on multiple vendor technologies, sometimes requiring parallel groups specializing in each(72)Hence, additional maintenance procedures must be maintained and administrative records are(73). The duplication of transport facilities to carry(74)network traffic is an inefficient use of resources. And, not surprisingly, more technologies installed in a central office mean the necessity for more physical space, and an increase in power connections and power consumption. Migration of these(75)network elements to IP-based DCNs is a logical strategy.

A．prohibitive

B．feasible

C．connective

D．special

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第8题

is used to ensure the confidentiality, integrity and authenticity of the two end poin

ts in the private network.(72), an application-layer protocol, authenticates each peer in an IPsec transaction. IKE negotiates security policy, determining which algorithm may be used to set up the tunnel. It also handles the exchange of session keys used for that one transaction.Networks that use(73) to secure data traffic can automatically authenticate devices by using(74), which verify the identities of the two users who are sending information back and forth. IPsec can be ideal way to secure data in large networks that require(75) connections among many devices.

A．Certificate

B．Encryption

C．Tunnel

D．Presentation

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第9题

● WLANs are increasingly popular because they enable cost－effective connections among peop

● WLANs are increasingly popular because they enable cost-effective connections among people, applications and data that were not possible, or not cost-effective, in the past. For example, WLAN-based applications can enable fine-grained management of supply and distribution （66） to improve their efficiency and reduce （67）. WLANs can also enable entirely new business processes. To cite but one example, hospitals are using WLAN-enabled point-of-care applications to reduce errors and improve overall （68)care. WLAN management solutions provide a variety of other benefits that can be substantial but difficult to measure. For example, they can protect corporate data by preventing （69）through rogue access points. They help control salary costs, by allowing IT staffs to manage larger networks without adding staff. And they can improve overall network management by integrating with customers’ existing systems, such as OpenView and UniCenter. Fortunately, it isn’t necessary to measure these benefits to justify investing in WLAN management solutions, which can quickly pay for themselves simply by minimizing time-consuming （70） and administrative chores.

● WLANs are increasingly popular because they enab

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第10题

Bluetooth is a universal radio interface in the（71)frequency hand that enables portable el

Bluetooth is a universal radio interface in the(71)frequency hand that enables portable electronic devices to connect and communicate wirelessly via short-range, ad hoc networks. Each unit can simultaneously communicate with up to(72)other units per piconet. Moreover, each unit can simultaneously(73)to several piconets. Eliminates the need for wires, cables and connectors for and between cordless or mobile phones, modems, headsets, PDAs, Computers, printers, projectors, local area networks, and so on, and paves the way for new and completely different devices and applications. Technology Characteristics(74)symbol rate exploits maximum available(75)bandwidth。

A．1.95GHz

B．2.45GHz

C．4.45GHz

D．11.45GHz

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