大一計算機導論第九章

1、computing essentials 2008 chapter 9: communications and networks chapter outline page 1 of 14 communications (242) othe process of sharing data, programs, and information between two or more computers. oconnectivity - using computer networks to link people and resources. othe wireless revolution - t

2、he widespread use of mobile or wireless telephones. the single most dramatic change in connectivity and communications in the past five years ocommunications systems (243) - electronic systems that transmit data from one location to another sending and receiving devices - originate (send) as well as

3、 accept (receive) messages in the form of data, information, and/or instructions communication channel transmission medium that carries the message.connection devices - convert outgoing messages into packets that can travel across the communication channel and reverse the process for incoming messag

4、es.data transmission specifications - rules and procedures that coordinate the sending and receiving devicescommunications channels (244)oactually carry the data from one computer to another ophysical (wired) - a solid medium to connect sending and receiving devices.twisted pair - hundreds of copper

5、 wires.coaxial cable - a high-frequency transmission cable fiber-optic cable - transmits data as pulses of light through tiny tubes of glass.owireless (245)infrared - uses infrared light waves to communicate over short distances (line-of-sight)broadcast radio - uses special sending and receiving tow

6、ers called transceivers, which send and receive radio signals from wireless devicesmicrowave - communication through high-frequency radio waves and provides line-of-sight communication but over short distances. bluetooth is a form of microwave transmission satellite - amplified microwaves that use p

7、oint-to-point communication to relay devices (satellites) orbiting the earth. communication interferences can occur in bad weather.connection devices (247)omodems - connection computers over analog phone lines. the convert the computers digital signal to an analog transmission to send over the phone

8、 line (modulation) and then re-convert it to digital when receiving information from the phone lines (demodulation). transfer rate is in bits-per-second.four types: internal, external, pc card, and wirelessoconnection service (248)digital subscriber line (dsl) - uses existing telephone lines to prov

9、ide high-speed connections. ( 30 mbps) computing essentials 2008 chapter 9: communications and networks chapter outline page 2 of 14 cable modems - use existing television cables to provide high-speed connections. ( 40 mbps) satellite/air connection (249) - use satellites and the air to download (do

10、wnlink) or send data to users. ( 900 kbps) cellular services - an alternative for mobile devices and laptops, using 3g cellular networks, devices such as cell phones and appropriately equipped laptop computers, use cellular towers to upload ( 50 kbps) or download ( 550kbps) data. data transmission (

11、249)obandwidth - a measurement of the width or capacity of the communication channel. basically, how much information can move across the communication channel in a given amount of time. voiceband (250)- used for standard telephone communication medium band - used in special leased lines broadband -

12、 used for high-capacity transmissions. oprotocols - a set of communication rules for the exchange of information. otcp/ip transmission control protocol/internet protocol identification: every computer on the internet has a unique numeric address called an ip address (internet protocol address). refo

13、rmatting: before a message is sent, it is reformatted or broken down into small parts called packets. networks (251)oa computer network is a communication system that connects two or more computers so that they can exchange information and share resources. onodeany device that is connected to a netw

14、ork. oclient a node that requests and uses resources available from other nodes. oservera node that shares resources with other nodes. ohubthe center or central node for other nodes. onetwork interface cards (nic) expansion cards located within the system unit that connect the computer to a network

15、onetwork operating systems (nos )control and coordinate the activities of all computers and other devices on a network. odistributed processing a system in which computing power is located and shared at different locations. ohost computer a large centralized computer onetwork managera computer speci

16、alist responsible for efficient network operations and implementation of new networks. network types (253)olocal area networks - networks with nodes that are in close physical proximity ohome networks (254) networks being used by individuals in their homes and apartments. ometropolitan area networks

17、 - span distances up to 100 miles. links between office buildings that are located throughout a city. owide area networks - countrywide and worldwide networks. network architecture (255)ohow a network is arranged and how resources are coordinated and shared.otopology computing essentials 2008 chapte

18、r 9: communications and networks chapter outline page 3 of 14 star - a number of small computers or peripheral devices are linked to a central unit. bus (258) - each device in the network handles its own communications control. there is no host computer. ring - each device is connected to two other

19、devices, forming a ring. there is no central file server. hierarchical networkconsists of several computers linked to a central host computer. however, these other computers are also hosts to other, smaller computers or to peripheral devices. making it work for you (256)ohome networking setup and co

20、nfiguration installation using windows xp using the network file sharing, printer sharing, and internet access strategies (260)terminal network system - processing power is centralized in one large computer, and the nodes connected to this host computer are either terminals with little or no process

21、ing capabilities.client/server network systems - use one computer to coordinate and supply services to other nodes on the network. the server provides access to resources peer-to-peer network system (261) - nodes have equal authority and can act as both clients and servers. many current popular musi

22、c sharing services use this network strategy. organizational internets (262)ointranet a private network within an organization that resembles the internet. use browsers, web sites, and web pages provide e-mail, mailing lists, newsgroups, and ftp services accessible only to those within the organizat

23、ion. oextranet a private network that connects more than one organization. many organizations use internet technologies to allow suppliers and others limited access to their networks. increase efficiency and reduce costs. ofirewalls (263)a security system designed to protect an organizations network

24、 against external threats. consists o f hardware and software that control access to a companys intranet or other internal networks. careers in it (264)onetwork administrators manage a company s lan and wan networks. oresponsibilitiesdesign, implementation, and maintenance of networks. maintenance o

25、f both hardware and software related to a companys intranet and internet networks. diagnosing and repairing problems with these networks. planning and implementations of network security computing essentials 2008 chapter 9: communications and networks chapter outline page 4 of 14 obachelor s degree

26、in computer science and practical networking experience or technical certification. oannual salary of $43,000 to $68,000. ofastest-growing jobs in the near future. a look to the future (265)ocars that monitor and respond to your moods, watch out for pedestrians, and communicate with other cars otoyo

27、ta and sony are collaborating on a car called pod , personalization on demand. odesigned to learn and adapt to your driving habits and needs. oconnects wirelessly to a portable terminal called the mini pod to share data and serve the users needs.ocan even communicate with other cars by using a horn

28、messaging system. olocates pedestrians and warns the driver to correct speed or course to avoid them.computing essentials 2008 chapter 9: communications and networks teaching tips page 5 of 14 communications (242)oit is good to emphasize that connectivity is the fastest growing sector of the compute

29、r industry and that the wireless revolution is the single most dramatic change in connectivity and communications in the past five years oyou can give an overview of the different parts of a communication system that will be covered. oyou can refer to the basic communications model that is discussed

30、 in public speaking classes and how computers work in the same fashion. sending and receiving devicescommunication channel = medium connection devicesdata transmission specifications = messagecommunications channels (244)oemphasize that there are two types of channels ophysical (wired) - a solid med

31、ium to connect sending and receiving devices.mention that twisted pair uses copper wires to conduct electricity, covers the least distance and is the slowest of the wired channelscoaxial cable - a high-frequency transmission cable, uses copper wire to conduct electricity, has the medium-range distan

32、ce capability and spped. fiber-optic cable - transmits data as pulses of light through tiny tubes of glass or plastic, covers the farthest distance and has the fastest transmission sppedowireless (245)infrared - uses infrared light waves to communicate over short distances (line-of-sight)broadcast r

33、adio - uses special sending and receiving towers called transceivers, which send and receive radio signals from wireless devicesmicrowave - communication through high-frequency radio waves and provides line-of-sight communication but over short distances. bluetooth is a form of microwave transmissio

34、n satellite - amplified microwaves that use point-to-point communication to relay devices (satellites) orbiting the earth. communication interferences can occur in bad weather.connection devices (247)oyou can emphasize the difference between modems and higher speed devices.omost students are familia

35、r with both and are interested in how you can connect using the higher speed devices.data transmission (249)obandwidth can be difficult for students to understand. you can use an analogy of a highway and the wider the road the more cars you can get across. oprotocols can be compared to foreign servi

36、ces and how different countries have different ways to communicate networks (251)oyou can emphasize the basic parts that comprise a network. ofigure 9-15 is a good illustration of all the parts of a network network types (253)computing essentials 2008 chapter 9: communications and networks teaching

37、tips page 6 of 14 othe divisions between the types of networks are not as clear cut from a technical perspective because some types of devices that used to be solely used for a wan can be used in lan environments. some students can point this fact out. it is best to state that you are taking this fr

38、om a geographical perspective. omany students have installed or want to install a home network. the making it work for you section on page 256 in conjunction with the expanding your knowledge exercise #1 can help create a good lab for the students to learn about setting up a home network. network ar

39、chitecture (255)ohow a network is arranged and how resources are coordinated and shared.ofigures 9-18 through 9 -20 in the text provide a good diagram of the different topologies. you can use these in a lecture to help illustrate your points strategies (260)most of the students have had experiences

40、with napster and other types of downloading programs. you can use these as an example of how client/server and peer-to-peer work. organizational internets (262)ointranet emphasize that it isa private network within an organization that resembles the internet. and it provides services accessible only

41、 to those within the organization. oextranet emphasize that it is a private network that connects more than one organization to allow suppliers and others limited access to their networks. good examples are organizations that use just in time inventory. ofirewall you can emphasize that firewalls are

42、 a good idea for home use too. ocan even communicate with other cars by using a horn messaging system.olocates pedestrians and warns the driver to correct speed or course to avoid them.computing essentials 2008 chapter 9: communications and networks key terms page 7of 14 key terms key term definitio

43、n 3g cellular network (249) 蜂窩通信網(wǎng)，細胞網(wǎng)絡(luò)cellular seljul ? cellular的中文含義是蜂窩(技術(shù) )，它是一種無線通信技術(shù)。這種技術(shù)把一個地理 區(qū)域分成若干個小區(qū)， 稱作 蜂窩 ( 即 cell) ，蜂窩技術(shù)因此而 得名 。手機 (或移動 電話 )均采用這項技術(shù)，因此常常被稱作蜂窩電話(cellular phone)。將一個大的地理區(qū)域分割成多個 蜂窩 的目的，是充分利用有限的無線傳輸頻率。每一組連接 (對于 無線電話而言就是每一組會話 )都需要專門的頻率，而可以使用的頻率一共只有大約 1000 個。為了使更多的會話能同時進行，蜂窩系統(tǒng)把給

44、每一個蜂窩 (即每一個小的區(qū)域 )分配了一定數(shù)額的頻率。不同的蜂窩可以使用相同的頻率，這樣，有限的無線資源就可以充分利用了。常見的蜂窩系統(tǒng)包括gsm 和cdma ，它們都屬于第二 代通信技術(shù)。a computer network that allows users to download data from the internet at 400 to 700 kbps using cell phone technology. analog signal (247) 模擬信號continuous electronic waves. asymmetric digital subscriber l

45、ine (adsl) (248) 非對稱數(shù)字用戶線路；不對稱數(shù)字訂閱線路 ；非對稱數(shù)字用戶線asymmetric ,?simetrik,-k ?l adj. 不對稱的；非對稱的 subscriber s?bskraib? n. 訂戶；簽署者；捐獻者the most widely used types of dsl. backbone (258) backbone b?kb ?un n. 支柱；主干網(wǎng)；決心，毅力；脊椎a common connecting cable on which all communications travel along. (see also bus) bandwid

46、th (249)n. 電子 物 帶寬； 通信 頻帶寬度a measurement of the width or capacity of the communication channel. base station (254) 基站；基電臺a network s centrally located receiver that interprets incoming radio frequencies and routes communications to the appropriate devices. (see also wireless receiver) bits per secon

47、d (bps) (247) 位 /秒how transfer speed is measured bluetooth (245) a short-range wireless communication standard that uses computing essentials 2008 chapter 9: communications and networks key terms page 8of 14 n. 藍牙技術(shù)（一種無線通信的標準）microwaves to transmit data over short distances broadband (250) n. 寬頻；寬波段

48、adj. 寬頻帶的；寬波段的；寬頻通訊的the bandwidth used for high-capacity transmissions. broadcast radio (245) 無線電波 廣播無線電uses radio signals to send and receive signals from wireless devices. bus (258) 總線a common connecting cable on which all communications travel along. (see also backbone) bus network (258) 總線網(wǎng)each

49、device in the network handles its own communications control. cable modem (249) 電纜調(diào)制解調(diào)器use existing television cables to provide high-speed connections to the internet. cellular service (249) 蜂窩電話服務offer an alternative for mobile devices and laptops. client (251) n. 經(jīng) 客戶；顧客；委托人a node that requests a

50、nd uses resources available from other nodes. client/server network system (260) 客戶機 /服務器網(wǎng)絡(luò)系統(tǒng)a computer network where one computer coordinates and supplies services to other nodes on the network. coaxial cable (244)n. 電 同軸電纜coaxial k ?u?ks ?l adj. 同軸的 ,共軸的a high-frequency transmission cable with a s

51、ingle solid-copper core. communication channel (244) 通信 通信信道；通信電路the actual connecting or transmission medium that carries the message. communication system (243) 通信 通信系統(tǒng)an electronic system that transmit data from one location to another computer network (251) 計算機網(wǎng)絡(luò)a communication system that conne

52、cts two or more computers so that they can exchange information and share resources. connectivity (242) n. 數(shù) 連通性using computer networks to link people and resources. demodulation (247) 解調(diào)demodulation di:,m ?djulei ?n n. 檢波；反調(diào)制；解調(diào)制the process of converting from analog to digital. dial-up service (248

53、) 撥號服務using standard telephone lines and conventional modems to link to the internet or other computers digital signal (247) 數(shù)字信號a representation of the presence or absence of an electronic pulse on/off digital subscriber line (dsl) (248) 數(shù)字用戶線 , 數(shù)字用戶線路uses existing telephone lines to provide high-s

54、peed connections distributed data processing system (258)分部數(shù)據(jù)處理系統(tǒng), 分布式數(shù)據(jù)處理computers that can perform processing tasks at their own dispersed locations. distributed processing (251) 分布處理 ,分散式處理方式a system in which computing power is located and shared at different locations. domain name server (dns) (

55、250) 域名服務器converts text-based addresses to ip addresses ethernet (253) the most common way in which nodes can be connected computing essentials 2008 chapter 9: communications and networks key terms page 9of 14 n. 計 以太網(wǎng)to one another and communications can be controlled. external modem (247) 外置調(diào)制解調(diào)器a

56、 modem that stands apart from the computer and typically is connected by a cable to the computers serial port. extranet (262) extranet是一個使用internet/intranet 技術(shù)使企業(yè)與其客戶和其它企業(yè)相連來完 成 其 共 同 目 標 的 合 作 網(wǎng) 絡(luò) 。extranet 可以作為公用的internet 和專用的 intranet 之間的橋梁，也可以被看作是一個能被企業(yè)成員訪問或與其它企業(yè)合作的企業(yè)intranet 的一部分。a private netw

57、ork that connects more than one organization. fiber-optic cable (244) 光纜 光纖電纜transmits data as pulses of light through tiny tubes of glass. firewall (263) 防火墻a security system designed to protect an organizations network against external threats. global positioning system (gps) (245) 全球定位系統(tǒng)global po

58、sitioning system (gps) devices use location information sent by satellites to uniquely determine the geographic location of the device. hierarchical network (258) 層次網(wǎng)絡(luò)，分層網(wǎng)絡(luò)consists of several computers linked to a central host computer, but also are hosts to other, smaller computers or peripheral de

59、vices. home network (254) 本地網(wǎng)絡(luò) ,家庭網(wǎng)local area networks used by individuals in their homes and apartments. host computer (251) 主機a large centralized computer, usually a minicomputer or a mainframe. hub (251) 集線器，中心所在the center or central node for other nodes. infrared (245) 紅外線的a type of wireless con

60、nection that uses infrared light waves to communicate over short distances. internal modem (248) 內(nèi)部調(diào)制解調(diào)器a modem that consists of a plug-in circuit board inside the system unit. intranet (262) 企業(yè)內(nèi)部互聯(lián)網(wǎng)a private network within an organization that resembles the internet. ip address (internet protocol a