Internet is a network of interconnected networks. This network has （)A. peopleB. comput

●(74) is a worldwide network of computer networks.

(74)

A. Modem

B. Interface

C. Internet

D. Protocol

A. VLANs establish broadcast domains in switched networks.

B. VLANs utilize packet filtering to enhance network security.

C. VLANs provide a method of conserving IP addresses in large networks.

D. VLANs provide a low-latency internet working alternative to routed networks.

E. VLANs allow access to network services based on department, not physical location.

F. VLANs can greatly simplify adding, moving, or changing hosts on the network.

从供选择的答案中选出应填入下面一段英文中______内的正确答案。

A brouter is a network bridge and a router combined in a single product. A bridge is a device that connects one local area network (LAN) to(1)local area network that uses the same protocol (for example,(2)or Token Ring). If a data unit on one LAN is intended for a(3)on an interconnected LAN, the bridge forwards the data unit to that LAN; otherwise, it passes it along on the same(4). A bridge usually offers only one path to a given interconnected LAN. A router connects a network to one or more other(5)that are usually part of a wide area network (WAN) and may(6)a number of paths out to destinations on those networks. A router therefore needs to have(7)information than a bridge about the interconnected networks. It(8)a routing table for this information. Since a given outgoing data unit or packet from a computer may be intended for an(9)on the local network, on an interconneted LAN, or the wide area network, it makes sense to have a single unit that(10)all data units and forwards them appropriately.

供选择的答案：

1．more 2．LAN 3．Ethernet 4．address 5． offer

6．destination 7．consults 8．another 9．networks 10．examines

esidency (总统任期) in the 1950s was the U.S. interstate highway system.It was a ____ project, easily surpassing the scale of such previous human ____ as the Panama Canal. Eisenhower’s interstate highways ____ the nation together in new ways and ____ major economic growth by making commerce less ____. Today, an information superhighway has been built—an electronic network that ____ libraries, corporations, government agencies and ____. This electronic superhighway is called the Internet, ____ it is the backbone (主干) of the World Wide Web.

The Internet had its ____ in a 1969 U.S. Defense Department computer network called ARPAnet, which ____ Advanced Research Projects Agency Network. The Pentagon built the network for military contractors and universities doing military research to ____ information. In 1983 the National Science Foundation (NSF), ____ mission is to promote science, took over.

This new NSF network ____ more and more institutional users, may of ____ had their owm internal networks. For example, most universities that ____ the NSF network had intracampus computer networks. The NSF network ____ became a connector for thousands of other networks. ____ a backbone system that interconnects networks, internet was a name that fit.

So we can see that the Internet is the wired infrastructure (基础设施) on which web ____ move. It began as a military communication system, which expanded into a government-funded ____ research network.

Today, the Internet is a user-financed system tying intuitions of many sorts together ____ an “information superhighway.”

A．concise

C．massive

B．radical

D．trivial

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

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

(总统任期)in the 1950s was the U. S. interstate highway system. It was a 【B1】 project, easily surpassing the scale of such previous human 【B2】 as the Panama Canal. Eisenhower's interstate highways 【B3】 the nation together in new ways and 【B4】 major economic growth by making commerce less—【B5】 . Today, an information superhighway has been built—an electronic network that 【B6】 libraries, corporations, government agencies and 【B7】 . This electronic superhighway is called the Internet, 【B8】 it is the backbone (主干)of the World Wide Web.

The Internet had its 【B9】 in a 1969 U. S. Defense Department computer network called ARPA net, which 【B10】 Advanced Research Projects Agency Network. The Pentagon built the network for military contractors and universities doing military research to 【B11】 information. In 1983 the National Science Foundation (NSF) , 【B12】 mission is to promote science, took over.

This new NSF network 【B13】 more and more institutional users, many of 【B14】 had their own internal networks. For example, most universities that 【B15】 the NSF network had intercampus computer networks. The NSF network 【B16】 became a connector for thousands of other networks. 【B17】 a backbone system that interconnects networks, internet was a name that fit.

So we can see that the Internet is the wired infrastructure(基础设施)on which web 【B18】 move. It began as a military communication system, which expanded into a government-funded 【B19】 research network.

Today, the Internet is a user-founded system tying institutions of many sorts together 【B20】 an "information superhighway."

【B1】

A．concise

B．radical

C．massive

D．trivial