● The connection between two networks to form. an internet is handled by a machine known as a （71） .（71）A．bridgeB．clientC．routerD．switch

The connection between two networks to form. an internet is handled by a machine known as a ______．

A．bridge

B．client

C．router

D．switch

For (71) service, we need a virtual-circuit subnet. Let us see how that works. The idea behind virtual circuits is to avoid having to choose a new (72) for every packet sent. Instead, when a connection is established, a route from the (73)machine to the destination machine is chosen as part of the connection setup and stored in tables inside the (74) That route is used for all traffic flowing over the connection, exactly the same way that the telephone system works. When the connection is released, the virtual circuit is also terminated. With connection-oriented service, each packet carries an (75) telling which virtual circuit it belongs to.

A．connectionless

B．connection-oriented

C．datagram

D．telegram

Networks can be interconnected by different devices in the physical layer networks can be connected by (71) 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 (72) ，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 (73) network layer，the router may be able to translate betweenthe 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 (74) ．As an example，gateways between Internet e-mail and X，400 e-mail must (75) thee-mail message and change various header fields．

(68)

A．reapers

B．relays

C．packages

D．modems

The presentation layer is concerned with the(71) and semantics of the information exchanged between two systems．The processes in two systems are usually exchanging information in the form. of character (72) numbers, and so on．The information should be changed to bit (73) before being transmitted．Because different computers use different encoding systems, the presentation layer is responsible for (74) between these different encoding methods．The presentation layer at the sender changes the information from its sender-dependent format into a common format． The presentation layer at the receiving machine changes the common format into its (75) dependent format．

(71)

A.frequency

B.syntax

C.dialog

D.format

(72)

A.numbers

B.unctions

C.strings

D.codes

(73)

A.systems

B.characters

C.layers

D. streams

(74)

A.capability

B.interoperability

C.reliability

D.dependability

(75)

A.receiver

B.user

C.server

D. customer

A. FTP

B. VLAN

C. VPN

D. HTTP

The(71) program is generally translated to an object program, which is in a form. directly understandably by the computer。

A．transfer

B．assemble

C．source

D．compile

●The presentation layer is concerned with the _(71) and semantics of the informationexchanged between two systems． The processes in two systems are usually exchanginginformation in the form. of character (72)-,numbers, and so on． The information should be changed to bit (73) before ．being transmitted． Because different computers use different encoding systems, the presentation layer is responsible for (74) between these different encoding methods． The presentation layer at the sender changes the information from its sender-dependent format into a common format． The presentation layer at the receiving machine changes the common format into its (75) dependent format．

(71)A．frequency B．syntax C．dialog D．format

(72)A．numbers B．functions C．strings D． codes

(73)A．systems B．characters C．layers D． streams

(74)A．capability B．interoperability C．reliability D．dependability

(75)A．receiver B．user C．server D． customer

An Intranet is (71) the application of Internet technology within an internal or closed user group．Internets are company and not do not have a (72) connection to the Internet．Usedproperly an Internet is highly effective corporate tool，capable of regularly (73) information toempower the workforce with the information needed to perform. their roles．Used in this Way，Internet represent a step towards the (74) office．

(84)

A．simple

B．simply

C．singlc

D．singly

● The Internet is the world
s largest computer (71) .

(71)

A.network

B.device

C.display

D.disk

● A glue that holds the whole Internet together is the network layer protocol,(71). Unlike most older network layer protocols, it was designed from the beginning with internetworking in mind. Its job is to provide a -(72) way to transport datagrams from source to destination, without regard to whether these machines are on the same network or whether there are other networks in between them.

Communication in the Internet works as follows. The (73)layer takes data streams and breaks them up into datagrams. Each datagram is transmitted through the Internet, possibly being fragmented into smaller units as it goes. When all the pieces finally get to the destination machine, they are reassembled by the

(74) layer into the original datagram. This datagram is then handed to the transport layer, which inserts it into the receiving process' input stream.

An IP datagram consists of a header part and a text part. The header has a (75) part and a variable length optional part.

(71) A. IP (Internet Protocol)

B. IP (Interworking Protocol)

C. TCP (Transport Control Protocol)

D. TCP (Transfer Communication Protocol)

(72) A. best-quality

B. quality-guaranteed

C. connection-oriented

D. best-efforts

(73) A. data link

B. transport

C. network

D. application

(74) A. data link

B. transport

C. network

D. application

(75) A. 40-byte fixed

B. 64-byte fixed

C. 20~64 bytes variable

D. 20-byte fixed

An Intranet is(71)the application of Internet technology within an internal or closed user group．Internets are company(72)and do not have a(73)connection to the Internet．Used properly an Internet is highly effective corporate tool，capable of regularly(74)information to empower the workforce with the information needed to perform. their roles．Used in this way，Internet represent a step towards the(75)office．

(58)

A．simple

B．simply

C．single

D．singly

While the Internet is inherently insecure, businesses still need to preserve the privacy of data as it travels over the network. To help do that, the Internet Engineering Task Force an international group of network designers, operators, vendors, and researchers concerned with the evolution of(71)has developed a suite of(72)called Internet Protocol Security(IPSec).

IPSec creates a standard platform. to develop secure networks and electronic(73)between two machines. Secure tunneling via IPSec creates(74)connections in a network through which data packets can move. It creates these tunnels between remote users and within a local network. It also(75)each data packet in a new packet that contains the information neccessary to set up, maintain and tear down the tunnel when it's no longer needed.

A．channels

B．Web browser

C．Internet data

D．Internet architecture

A.0

B.1

C.2

D.4

The part of the computer that runs the program is known as（71）

A.sofiware

B.memory

C.CPU

D.storage

●(71) devices are interface of man and machine.

(71) A． I/O

B．Memory

C．Disk

D．Printer