计算机英语刘艺王春生第4版省公共课一等奖全国赛课获奖课件.pptx
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1、UNIT 9 The Internet Section A The Internet1第1页 The most notable example of an internet is the Internet(note the uppercase l),which originated from research projects going back to the early 1960s.The goal was to develop the ability to link a variety of computer networks so that they could function as
2、 a connected system that would not be disrupted by local disasters.最著名著名互联网例子是因特网(Internet,注意大写)。因特网起源于20世纪60年代初研究项目。其目标是发展一个能力,将各种计算机网络连接起来,使它们能够作为一个不会因局部灾难而瓦解瓦解互联络统运行。Introduction2第2页Most of this original work was sponsored by the U.S.government through the Defense Advanced Research Projects Agenc
3、y(DARPA-pronounced DAR-pa).Over the years,the development of the lnternet shifted from a defense project to an academic research project,and today it is largely a commercial undertaking that links a worldwide combination of WANs,MANs,and LANs involving millions of computers.最初工作大多是由美国政府经过国防部高级研究计划局(
4、DARPA读作“DAR-pa”)发起。伴随岁月推移,因特网开发从一个国防项目转变成一个学术研究项目。如今,它在很大程度上是一个商业项目项目,连接着全世界广域网、城域网和局域网,包括数百万台计算机。Introductionshifted from.to.从.转为shift from 从.去掉(移开)3第3页I.Internet Architecture Conceptually,the internet can be viewed as a collection of domains,each of which consists of a network or a relatively smal
5、l internet operated by a single organization such as a university,company,or government agency.Each domain is an autonomous system that can be configured as the local authority desires.I.因特网体系结构因特网体系结构 从概念上说,因特网能够看作是域域集合。每个域由一个网络或一个相对较小互联网组成,由一个像大学、企业或政府机构那样组织负责运行。每个域是一个自主自主系统,可依据当地管理机构愿望进行配置。Intern
6、et Architecture4第4页It might consist of a single computer or a complex internet consisting of many LANs,MANs,and even WANs.The establishment of domains is overseen by the Internet Corporation for Assigned Names and Numbers(ICANN),它可能由一台计算机或一个包含许多局域网、城域网、甚至广域网复杂互联网组成.域建立由互联网名称与数字地址分配机构(ICANN)监管监管,Inte
7、rnet Architecture5第5页which is a nonprofit corporation established to coordinate the naming of domains and the assignment of Internet addresses.To establish a domain on the Internet.the domain must first be registered via one of the companies,called registrars,that have been delegated for this purpos
8、e by ICANN.这是一个非赢利非赢利企业,其成立目标是协调域命名及因特网地址分配。要在因特网上建立一个域,该域必须首先经过一个得到ICANN授权授权做此工作、被称为域名注册服务商企业进行注册注册。Internet Architecture6第6页 Once a domain has been registered,it can be attached to the existing lnternet by means of a router that connects one of the networks in the domain to a network already in th
9、e Internet.This particular router is often referred to as the domains gateway,in that it represents the domains gate to the rest of the Internet.一个域一旦注册,即能够使用一个路由器连接到现有因特网上。这个路由器路由器将该域中一个网络与已经在因特网内一个网络相连接。这个特定路由器常被称为该域网关网关,因为它相当于该域通往因特网其余部分大门。Internet Architecture7第7页From the point of view of a sing
10、le domain,the portion of the lnternet lying outside of its gateway is sometimes called the cloud,in reference to the fact that the structure of the internet outside the domains gateway is out of the domains control and is of minimal concern to the operation of the domain itself。从单个域角度看,位于其网关外面那部分因特网
11、有时被称为“云”,这是指这是指以下事实:其网关外面因特网结构不受其控制,而且与其本身操作也没有什么关系。Internet Architecture就.而论is of+抽象n:作为表语表示主语性质或特征。意思是“含有,具备”,如:be of success=be successful be of use=be useful8第8页Any message being transmitted to a destination within the domain is handled within the domain;any message being transmitted to a destin
12、ation outside the domain is directed toward the gateway where it is sent out into the cloud.传输给该域内一个目标地任何报文都在该域内处理,传输给该域外一个目标地任何报文都首先送至网关,然后由网关向外发送到云里。Internet Architecture9第9页 If one stood at a domains gateway and looked out into the cloud,one could find a variety of structures.Indeed,the lnternet
13、has grown in a somewhat haphazard way as various domains have found points at which to connect to the cloud.One popular structure,however,is for the gateways of a number of domains to be connected to form a regional network of gateways.一个人假如“站”在一个域网关处“向外看”云,就会发觉各种结构。确实,伴随各种域找到与云建立连接点,因特网也以有点随意有点随意方式
14、发展着。然而,一个流行结构是,将若干域网关连接在一起,形成一个由网关组成区域网络。Internet Architecture支持/赞成,是为了.10第10页For instance,a group of universities could choose to pool their resources to construct such a network.In turn,this regional network would be connected to a more global network to which other regional networks attach.In thi
15、s manner,that portion of the cloud takes on a hierarchical structure(Figure 9A-I).比如,一组大学能够选择将其资源集中起来,用于构建这么一个网络。而这个区域网络接着又连接到一个更大大网络上,后者上面还连接有其它区域网络。这么,那部分云就展现出了层次结构(图9A-1)。Internet Architecture轮番地、依次11第11页II.Connecting to the lnternet To simplify the process of connecting to the Internet,numerous
16、companies,called Internet service providers(ISPs),allow customers to connect their domains to the Internet via the ISPs equipment or to become a part of a domain already established by the ISP.II 连接到因特网连接到因特网 为了简化连接到因特网上过程,许多称为因特网服务提供商企业允许客户经过企业设备将他们域连接到因特网上,或者成为企业已经建立一个域一部分Connecting to the Interne
17、t12第12页Perhaps the least expensive connections to an ISP are obtained through temporary telephone links called dial-up connections.Using this approach,an individual connects his or her computer to the local telephone line and executes a software package that places a call to a computer at the ISP.At
18、 this point the ISP provides lnternet access for the duration of the telephone call.与因特网服务提供商最经济连接或许是经过暂时电话链路建立连接,这种连接称为拨号拨号连接。使用这种方法,一个人将其计算机连接到当地电话线上,然后运行一个软件包,向因特网服务提供商一台计算机发出呼叫。这时,因特网服务提供商就为其提供因特网访问服务,连续时间为电话呼叫时间长度Connecting to the Internet13第13页 This temporary connection model is popular(and,in
19、 fact,expanding)in the cell phone/hand-held computer area.However,in fixed location applications it is rapidly giving way to permanent connections through higher bandwidth systems such as DSL,cable television lines,and satellite links.这种暂时连接模型在手机手机/手持式计算机手持式计算机领域比较流行(实际上应用得越来越多)。然而,在位置固定应用中,暂时连接快速让位
20、于永久连接,这种连接经过数字用户线路、有线电视线路和卫星链路等带宽带宽比较高系统建立Connecting to the Internetgive way to 让路,让步give way 让步,屈服,垮掉14第14页These technologies have greatly reduced the expense of broadband(high-capacity)lnternet access(which used to be availible only to large organizations that could afford the expense of dedicated
21、 lnternet connections),making todays multimedia applications accessible to home users.这些技术大大降低了宽带(大容量)因特网访问(曾经只提供给负担得起专用因特网连接大型机构)费用,从而使家庭用户也能够访问今天多媒体多媒体应用程序。Connecting to the Internet15第15页 Another development taking place at the household level is that home computer systems are expanding from sing
22、le computer installations to multicomputer networks,usually implemented as Ethernet bus networks.These networks gain access to the Internet by means of a router within the home that is permanently connected to an ISP via DSL,a cable television line,or a satellite link,在家庭层面出现另外一个发展是,家用计算机系统正在从单个计算机设
23、备扩展为多个计算机网络,这种网络通常实现实现为以太网总线网络。这些网络使用家里路由器访问因特网,而该路由器经过数字用户线路数字用户线路、有线电视线路或卫星链路与因特网服务提供商永久连接,Connecting to the Internet16第16页making the home system a local network within a domain established by the ISP.The connection from the homes router to the local computers is often wireless.That is,each comput
24、er communicates with the router by means of a small transmitter/receiver with a range of approximately 100 feet.从而使家里系统成为因特网服务提供商建立一个域中局部网.从家中路由器到家庭局部网中计算机连接经常采取无线方式。也就是说,每台计算机使用一部作用距离大约为100英尺小型发射机发射机/接收机与路由器通信。Connecting to the Internet17第17页Such wireless local networks are popular outside the home
25、 as well where they are used to create hotspots in which any wireless-enabled computer(laptop or hand held)that comes within range can access the Internet.Examples include office buildings,cyber cafes,public plazas and entire cities.这种无线局部网在家庭之外也很流行,被用于建立热区热区。在这些热区范围内,任何含有没有线上网能力计算机(膝上型或手持式计算机)均可访问因
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