计算机专业英语教程第4版译文52Word文档下载推荐.docx

1、一个国家中多个主干网连接到每个国家中的主要高速网络称为主干网。Backbone networks within a country are connected together and to backbone networks in other countries to form the Internet.一个国家中的多个主干网的连接及与其他国家中的主干网的连接就形成了因特网。The following sections discuss the most common types of Internet connections.下面部分讨论了大部分常用的因特网连接类型。1.Dial-Up Co

2、nnections拨号连接Dial-up connections usually work over regular telephone lines.regular 正规的拨号连接通常工作在正规的电话线。To connect to the Internet, your modem （or other appropriate interface device ） dials up and connects to a modem attached to your ISPs computer.modem 调制解调器为了连接到因特网，你的调制解调器（或其他适当的接口设备）拨号然后连接到附属于你的因特网

3、服务提供商的计算机的调制解调器。While you are connected, your PC is assigned a temporary IP address for the current session.当你连接上了，你的电脑被指派一个用于当前会话的临时的IP地址。At the end of each Internet session, you disconnect from your ISPs computer to allow another user to connect in your place.disconnect 断开一个网络连接在每一次因特网会话结束时，你从你的因特

4、网服务提供商的计算机上断开一个网络连接以允许处于你位置的其他用户去连接。One advantage to a dial-up connection is security.拨号连接的一个优势是安全。Since you are not continually connected, it is much less likely that anyone would gain access to your computer via the Internet, to either obtain information or mess with the data on your PC or, more c

5、ommonly, to user your computer in some type of illegal or unethical manner.via 经由mess with 搞糟 打扰illegal 非法的因为你不持续地连接，所以不大可能有人能经由因特网获得你计算机的访问，或者获得你的PC上的信息或者搞糟电脑的数据，或者更常见的是以某种不合法或者不道德的方式使用你的计算机。These types of hacking activities are discussed later.hacking 黑客行为这些不同类型的黑客行为活动后面将讨论。 With a dial-up connect

6、ion your telephone will be tied up while you are accessing the Internet, unlesss a second phone line is used.tied up 被占用使用拨号连接，当你正在访问因特网时你的电话将被占用，除非第二条电话线被使用。Some Internet call-waiting or call-forwarding services allow you to be notified when you get a telephone call while you are connected to the I

7、nternet.call-waiting 呼叫等待call-forwarding 自动转接在你连接了因特网期间，当来了一个电话呼叫时，一些因特网呼叫等待或者自动转接服务会通知你。They are generally set up to allow the person to leave a short message;它们通常设置允许人们留下一个简答的信息。some newer systems give you a short window of time to disconnect from the Internet and pick up the telephone call, if de

8、sired.一些新的系统给你一个较短的时间从因特网上断开然后拿起电话，如果你愿意。Newer dial-up modems are expected to facilitate some type of call-waiting service, as well.facilitate 促进新的拨号调制解调器被期望来促进某种类型的呼叫等待服务。Standard Dial-up标准拨号Standard dial-up Internet service uses a conventional dial-up modem rated at a maximum data transfer rate of

9、 56 Kbps.标准拨号因特网服务使用一个最大数据交换数度是56Kbps的传统的拨号调制解调器。These modems are commonly used with PCs and Internet appplicances.这些调制解调器通常用于PCs和因特网应用。Portable devices may also use a conventional dial-up modem; if so, they need to be connected to standard telephone jacks to access the Internet.Portable 便携的jacks 插座

10、便携的设备也使用传统的拨号调制解调器，假如这样，他们为了访问因特网需要连接到标准的电话插座上。Standard dial-up Internet service range from free to about $ 25 per month.标准的拨号因特网服务从免费到大约每个月25的范围内。ISDN综合业务数字网Another dial-up option is ISDN.另外一个拨号选择是综合业务数字网。ISDN（integrated services digital network） allows digital transmission of data over ordinary te

11、lephone lines.transmission 传输综合业务数字网允许通过不同的电话线进行数据的数字传输。It requires a special ISDN adapter or modem and can transfer data up to 128 Kpbs.它需要一个特殊的ISDN适配器或者调制解调器，可以传输数据达到128Kbps。2. Direct Connections直接相连Unlike dial-up connections that only connect to your ISPs computer when you need to access the Inte

12、rnet, direct connections keep you continually connected to the Internet.不像拨号连接那样，当你需要访问因特网时，只能连接到ISP的计算机上，直连使得你可以持续连接到因特网。With a direct （always-on） connection, your PC is typically issued a static （nonchanging） IP address to be used to transfer data back and forth via the Internet.issued 发布通过直连，你的PC

13、典型的发布一个用于经由因特网来回交换数据的静态IP地址。PCs connected to the network always have an Internet connection available-Internet access requires only opening a browser.电脑连接到网络总是有一个因特网连接可能的网络访问只需要打开一个浏览器。 Types of direct Internet connections include connecting through a school or office LAN, as well as DSL, cable, sat

14、ellite, and fixed wireless connections.Cable 电缆satellite 卫星直接的因特网连接类型包括通过一个学校或者政府机关的局域网以及数字用户线，电缆，卫星和固定无线连接进行连接。Though, in theory, broadband Internet access can be up to 100 times as fast as a dial-up connection, actual speeds at the present time are more like 25 to 50 times as fast.Theory 理论broadba

15、nd Internet access 宽带上网虽然,在理论上,宽带上网可以快速到拨号连接的100倍,实际现在的速度则更像是25到50倍。Typical download speeds for DSL and cable are about 1.5 Mbps;数字用户线和电缆的典型地下载速度大约是1.5Mbps。satellite and fixed wireless usually download data between 500 Kbps to 1 Mbps.卫星和固定无线通常下载数据在500Kbps到1Mbps之间。Virtually all of these services use

16、slower upload speeds.几乎所有这些服务使用较慢的上传速度。The most significant characteristics of each of these types of broadband Internet access are discussed next.每一种这些宽带上网的类型的最重要的特点将在后面讨论。School or Office LANMost school or office LANs that offer a direct connection to the Internet lease a high-speed dedicated line

17、 （such as an ISDN or T1 line） from the telephone company or an Internet provider.lease 租约dedicated 专用的大多数学校或者政府机关的局域网，提供一个与因特网直接相连的从电话公司或者因特网提供者那里租约一条高速专用线。The speed of this type of Internet access depends on the speed of the connection between the school or offices and their Internet provider, as w

18、ell as the speed of the LAN itself.这种类型的因特网接入速度依赖学校或者政府机关和它们的因特网提供者间的连接速度，同样也依赖于局域网本身的速度。DSLDSL （digital subscriber line） is currently available only to users who are relatively close （three miles or less ） to a telephone switching station with telephone lines capable of handling DSL, and long waits

19、 for installation are not uncommon.subscriber 用户capable 有能力的DSL目前只对那些较靠近电话交换站（3英里或小于3英里），有能力处理DSL电话线的用户可用，并且常要等很长时间安装。Nevertheless, DSL is a popular broadband option.Nevertheless 然而然而,DSL是一项很受欢迎的宽带的选择。DSL is sometimes offered at different speeds to fit different needs and budgets, such as a slower,

20、less-expensive personal version and a faster business option.Budgets 预算DSL有时提供不同的速度以满足不同的需要和预算，例如慢速低价的个人版本和快速的商业选择。The monthly cost of standard DSL service is about $50.标准DSL的每月消费大约是50美元。Cable电缆A third type of direct Internet connection-cable-is the most widely used home broadband alternative.Altern

21、ative 供选择的第三种因特网直连类型是电缆，它是最广泛使用的家庭宽度选择。Cable connections are very fast and are available to anyone with cable access whose cable provider has upgraded the system to support Internet access.upgraded 升级电缆连接是相当快的，可以让任何人通过电缆访问，电缆提供商升级了支持因特网访问的系统。Just about all cable Internet access today is two-way （ful

22、l-duplex）, with the cable being used to transfer data in both directions.今天几乎所有的电缆因特网访问是双向的（全双工），通过在两个方向上用来交换数据的电缆。One disadvantage of cable is that all users in an immediate geographical area share the bandwidth of their local cable.电缆的一个劣势是在邻近地区的所有用户共同使用他们本地电缆的带宽。Though this may not prove to be a

23、problem all the time, during high-use times of day-such as early evening-the speed of cable Internet service can slow down dramatically as your neighbors go online.dramatically 戏剧的尽管这并不能证明是一个问题，在一天的高使用时间电缆因特网服务的速度会变低，戏剧的你的邻居上线了。Cost is about $40 per month, in addition to regular cable fees.in additi

24、on to 除.之外fee 费用费用大概是每月40美元，除了常规的电缆费用外。Satellite卫星Satellite Internet access is often the only broadband option in rural areas.rural 农村的卫星因特网访问是在农村地区唯一的宽带选择。It requires a satellite modem and a transceiver satellite dish mounted outside the home or building.transceiver 收发器dish 蝶形天线mounted 安装它需要人造卫星调制解

25、调器和安装在室外或建筑物外的收发卫星蝶形天线。The two-way satellite services available today, such as StarBand, are relatively reliable, though an unobstructed view of the southern sky is requited and access may degrade very heavy rainstorms.虽然需要在蝶形天线收发方向的上空没有任何障碍，并且在大暴风雨期间访问性可能降低，但目前可用的两路人造卫星服务，如StarBand，是相当可靠的。Typical c

26、ost is about $70 per month.典型的费用大约是每月70美元。Fixed Wireless固定无线One last type of broadband access that is relatively new for consumer use but shows great promise is fixed wireless.最后一种宽度访问是固定无线，这种访问方式对消费者使用是相当新的，但显示出很大的前途。This type of service, such as Sprint Broadband Direct, is similar to satellite ser

27、vice in that it requires a modem and an outside-mounted transceiver, but is typically available only in larger metropolitan areas.metropolitan 大都市的这种服务的类型，例如Sprint Broadband Direct，像卫星服务一样需要一个调制解调器和一个外部安装的收发器，但通常只有在大的大城市地区。A clear line-or-sight is required between the transceiver and the providers r

28、adio transmission tower, which relays information between the users transceiver and the Internet.radio 无线电广播tower 塔relays 中继 转播在收发器和提供商的无线传输塔之间需要有一条无障碍的视线通路，传输塔在用户的收发器和Internet间转播信息。Cost for service is about $50 per month.这种服务的费用大约是每月50美元。 Regardless of the type of connection used, a very important

29、consideration for all users with a direct Internet connection is protecting the computer from unauthorized access or hackers.Regardless of 不管unauthorized XX的不管那种类型的连接被使用，对所有直接连接到因特网的用户一个非常重要的考虑是保护计算机不受XX的访问或者黑客的攻击。While most schools and offices are protected by some type of firewall, many home direct connections are not.然而大多数学校和政府机关通过一些防火墙来保护，许多直接连接的家庭则不是。Though it is unlikely that someone would access your home PC in this manner, the possibility will continue to incr