電子通信專業(yè)畢業(yè)論文外文翻譯--電信現(xiàn)代運(yùn)營(yíng)

1、<p><b>　　畢業(yè)設(shè)計(jì)</b></p><p><b>　?。ㄍ馕姆g材料）</b></p><p>　　Telecommunication Modern Operation</p><p><b>　　Telephone</b></p><p>　　In an

2、 analogue telephone network, the caller is connected to the person he wants to talk to by switches at various telephone exchanges. The switches form an electrical connection between the two users and the setting of these

3、 switches is determined electronically when the caller dials the number. Once the connection is made, the caller's voice is transformed to an electrical signal using a small microphone in the caller's handset. Th

4、is electrical signal is then sent through the network to the us</p><p>　　The fixed-line telephones in most residential homes are analogue — that is, the speaker's voice directly determines the signal'

5、;s voltage. Although short-distance calls may be handled from end-to-end as analogue signals, increasingly telephone service providers are transparently converting the signals to digital for transmission before convertin

6、g them back to analogue for reception. The advantage of this is that digitized voice data can travel side-by-side with data from the Internet and can be p</p><p>　　Mobile phones have had a significant impact

7、 on telephone networks. Mobile phone subscriptions now outnumber fixed-line subscriptions in many markets. Sales of mobile phones in 2005 totalled 816.6 million with that figure being almost equally shared amongst the ma

8、rkets of Asia/Pacific (204 m), Western Europe (164 m), CEMEA (Central Europe, the Middle East and Africa) (153.5 m), North America (148 m) and Latin America (102 m). In terms of new subscriptions over the five years from

9、 1999, Africa has</p><p>　　There have also been dramatic changes in telephone communication behind the scenes. Starting with the operation of TAT-8 in 1988, the 1990s saw the widespread adoption of systems b

10、ased on optic fibres. The benefit of communicating with optic fibres is that they offer a drastic increase in data capacity. TAT-8 itself was able to carry 10 times as many telephone calls as the last copper cable laid a

11、t that time and today's optic fibre cables are able to carry 25 times as many telephone calls as TAT</p><p>　　Assisting communication across many modern optic fibre networks is a protocol known as Asynch

12、ronous Transfer Mode (ATM). The ATM protocol allows for the side-by-side data transmission mentioned in the second paragraph. It is suitable for public telephone networks because it establishes a pathway for data through

13、 the network and associates a traffic contract with that pathway. The traffic contract is essentially an agreement between the client and the network about how the network is to handle th</p><p>　　Radio and

14、television</p><p>　　In a broadcast system, a central high-powered broadcast tower transmits a high-frequency electromagnetic wave to numerous low-powered receivers. The high-frequency wave sent by the tower

15、is modulated with a signal containing visual or audio information. The antenna of the receiver is then tuned so as to pick up the high-frequency wave and a demodulator is used to retrieve the signal containing the visual

16、 or audio information. The broadcast signal can be either analogue (signal is varied continuo</p><p>　　The broadcast media industry is at a critical turning point in its development, with many countries movi

17、ng from analogue to digital broadcasts. This move is made possible by the production of cheaper, faster and more capable integrated circuits. The chief advantage of digital broadcasts is that they prevent a number of com

18、plaints with traditional analogue broadcasts. For television, this includes the elimination of problems such as snowy pictures, ghosting and other distortion. These occur becau</p><p>　　In digital television

19、 broadcasting, there are three competing standards that are likely to be adopted worldwide. These are the ATSC, DVB and ISDB standards; the adoption of these standards thus far is presented in the captioned map. All thre

20、e standards use MPEG-2 for video compression. ATSC uses Dolby Digital AC-3 for audio compression, ISDB uses Advanced Audio Coding (MPEG-2 Part 7) and DVB has no standard for audio compression but typically uses MPEG-1 Pa

21、rt 3 Layer 2. The choice of modulation </p><p>　　However, despite the pending switch to digital, analogue receivers still remain widespread. Analogue television is still transmitted in practically all countr

22、ies. The United States had hoped to end analogue broadcasts on December 31, 2006; however, this was recently pushed back to February 17, 2009. For analogue television, there are three standards in use. These are known as

23、 PAL, NTSC and SECAM. For analogue radio, the switch to digital is made more difficult by the fact that analogue receivers</p><p>　　The Internet</p><p>　　The Internet is a worldwide network of c

24、omputers and computer networks that can communicate with each other using the Internet Protocol. Any computer on the Internet has a unique IP address that can be used by other computers to route information to it. Hence,

25、 any computer on the Internet can send a message to any other computer using its IP address. These messages carry with them the originating computer's IP address allowing for two-way communication. In this way, the I

26、nternet can be seen as a</p><p>　　An estimated 16.9% of the world population has access to the Internet with the highest access rates (measured as a percentage of the population) in North America (69.7%), Oc

27、eania/Australia (53.5%) and Europe (38.9%).In terms of broadband access, Iceland (26.7%), South Korea (25.4%) and the Netherlands (25.3%) lead the world. </p><p>　　The Internet works in part because of proto

28、cols that govern how the computers and routers communicate with each other. The nature of computer network communication lends itself to a layered approach where individual protocols in the protocol stack run more-or-les

29、s independently of other protocols. This allows lower-level protocols to be customized for the network situation while not changing the way higher-level protocols operate. A practical example of why this is important is

30、because it allows</p><p>　　For the Internet, the physical medium and data link protocol can vary several times as packets traverse the globe. This is because the Internet places no constraints on what physic

31、al medium or data link protocol is used. This leads to the adoption of media and protocols that best suit the local network situation. In practice, most intercontinental communication will use the Asynchronous Transfer M

32、ode (ATM) protocol (or a modern equivalent) on top of optic fibre. This is because for most intercon</p><p>　　At the network layer, things become standardized with the Internet Protocol (IP) being adopted fo

33、r logical addressing. For the world wide web, these “IP addresses” are derived from the human readable form using the Domain Name System (e.g. 72.14.207.99 is derived from www.google.com). At the moment, the most widely

34、used version of the Internet Protocol is version four but a move to version six is imminent. </p><p>　　At the transport layer, most communication adopts either the Transmission Control Protocol (TCP) or the

35、User Datagram Protocol (UDP). TCP is used when it is essential every message sent is received by the other computer where as UDP is used when it is merely desirable. With TCP, packets are retransmitted if they are lost a

36、nd placed in order before they are presented to higher layers. With UDP, packets are not ordered or retransmitted if lost. Both TCP and UDP packets carry port numbers with them</p><p>　　Above the transport l

37、ayer, there are certain protocols that are sometimes used and loosely fit in the session and presentation layers, most notably the Secure Sockets Layer (SSL) and Transport Layer Security (TLS) protocols. These protocols

38、ensure that the data transferred between two parties remains completely confidential and one or the other is in use when a padlock appears at the bottom of your web browser. Finally, at the application layer, are many of

39、 the protocols Internet users would be </p><p>　　Local area networks</p><p>　　Despite the growth of the Internet, the characteristics of local area networks (computer networks that run at most a

40、 few kilometres) remain distinct. This is because networks on this scale do not require all the features associated with larger networks and are often more cost-effective and efficient without them.</p><p>　

41、　In the mid-1980s, several protocol suites emerged to fill the gap between the data link and applications layer of the OSI reference model. These were Appletalk, IPX and NetBIOS with the dominant protocol suite during th

42、e early 1990s being IPX due to its popularity with MS-DOS users. TCP/IP existed at this point but was typically only used by large government and research facilities. As the Internet grew in popularity and a larger perce

43、ntage of traffic became Internet-related, local area networks</p><p>　　It is at the data link layer though that most modern local area networks diverge from the Internet. Whereas Asynchronous Transfer Mode (

44、ATM) or Multiprotocol Label Switching (MPLS) are typical data link protocols for larger networks, Ethernet and Token Ring are typical data link protocols for local area networks. These protocols differ from the former pr

45、otocols in that they are simpler (e.g. they omit features such as Quality of Service guarantees) and offer collision prevention. Both of these d</p><p>　　Despite the modest popularity of Token Ring in the 80

46、's and 90's, virtually all local area networks now use wired or wireless Ethernet. At the physical layer, most wired Ethernet implementations use copper twisted-pair cables (including the common 10BASE-T networks

47、). However, some early implementations used coaxial cables and some recent implementations (especially high-speed ones) use optic fibres. Optic fibres are also likely to feature prominently in the forthcoming 10-gigabit

48、Ethernet implem</p><p><b>　　電信現(xiàn)代運(yùn)營(yíng)</b></p><p><b>　　電話 </b></p><p>　　在一個(gè)模擬電話網(wǎng)絡(luò), 來(lái)電者通過(guò)交換機(jī)與對(duì)方進(jìn)行不同的電話交流?開關(guān)在兩用戶間形成一個(gè)電氣連接,其參數(shù)是由來(lái)電者按鍵時(shí)的電氣特性決定的? 一旦連接,來(lái)電者的聲音通過(guò)來(lái)電端處的電話

49、聽筒轉(zhuǎn)化為電信號(hào)?然后電信號(hào)通過(guò)網(wǎng)絡(luò)發(fā)送到另一端的用戶,并通過(guò)小型揚(yáng)聲器將信號(hào)轉(zhuǎn)化為聲音?有一個(gè)單獨(dú)的電氣連接用于進(jìn)行轉(zhuǎn)換,以使用戶交談? </p><p>　　固定電話 ,在多數(shù)居民區(qū)是模擬電話,那就是,發(fā)言者的聲音,直接決定著信號(hào)的電壓? 雖然距離短,來(lái)電可能會(huì)被作為模擬信號(hào)的端到端信號(hào)處理,越來(lái)越多電話服務(wù)供應(yīng)商是適度的在傳輸前將模擬信號(hào)數(shù)字化以便傳輸,之后轉(zhuǎn)為模擬信號(hào)以便接收?它的優(yōu)勢(shì)是,數(shù)字化語(yǔ)音數(shù)據(jù)可

50、以從互聯(lián)網(wǎng)上以數(shù)字形式傳輸,而且可以完全轉(zhuǎn)載于遠(yuǎn)程通信?(對(duì)比來(lái)看,模擬信號(hào)無(wú)可避免會(huì)受到噪聲影響?)</p><p>　　手機(jī)已對(duì)電話網(wǎng)絡(luò)產(chǎn)生了重大影響? 移動(dòng)電話用戶現(xiàn)在在許多市場(chǎng)超過(guò)了固定線路用戶? 手機(jī)銷量在2005年總額為8.166億,被一下數(shù)字平分,其中亞洲/太平洋(2.04億),西歐(1.64億),cemea(中歐,中東和非洲)(1.535億),北美(1.48億)和拉丁美洲(1.02億)?在從199

51、9年之后的五年時(shí)間內(nèi)新增用戶來(lái)看,非洲已以58.2 %的增長(zhǎng)超過(guò)了其他地區(qū)的市場(chǎng)?手機(jī)逐漸采用如GSM或W-CDMA這些可以數(shù)字化傳輸語(yǔ)音信號(hào)的系統(tǒng),從而使AMPS這樣的模擬系統(tǒng)衰落?</p><p>　　電話通信也隱約地有了戲劇性的變化?開始運(yùn)作的TAT-8(跨大西洋傳輸電纜)始于1988年, 20世紀(jì)90年代見證了基于光纖系統(tǒng)的普及?光纖傳輸?shù)膬?yōu)勢(shì)在于其所提供的數(shù)據(jù)容量的急劇增加?TAT-8可以傳輸相當(dāng)于同軸

52、電纜電話10倍的數(shù)據(jù),而現(xiàn)在的光纖能傳輸25倍于TAT-8的數(shù)據(jù)?數(shù)據(jù)能力的增加是由于幾個(gè)因素:第一,光纖體積遠(yuǎn)小于其他競(jìng)爭(zhēng)技術(shù)? 第二,他們不受到串?dāng)_這意味著數(shù)百條光纖可以很容易地捆綁在一個(gè)單一的電纜內(nèi)?最后,復(fù)用技術(shù)的改善導(dǎo)致了單條光纖數(shù)據(jù)容量的指數(shù)增長(zhǎng)?</p><p>　　基于現(xiàn)代光纖網(wǎng)絡(luò)的通信是一項(xiàng)稱為異步傳輸模式 ( ATM )的協(xié)議?如第二段所說(shuō),ATM協(xié)議允許為并排的數(shù)據(jù)傳輸?它適用于公共電話網(wǎng)絡(luò)

53、,因?yàn)樗⒘送ㄟ^(guò)網(wǎng)絡(luò)數(shù)據(jù)通道并以此進(jìn)行通信?傳輸協(xié)議基本上是一個(gè)用戶與網(wǎng)絡(luò)之間的協(xié)議,它規(guī)定了網(wǎng)絡(luò)如何來(lái)處理數(shù)據(jù);如果網(wǎng)絡(luò)不能滿足條件的傳輸協(xié)議,它不接受連接? 這很重要,因?yàn)殡娫捒梢酝ㄟ^(guò)協(xié)議,保證自己的恒定比特率,這將確保來(lái)電者的聲音,不是延遲的部分或完全切斷?ATM的競(jìng)爭(zhēng)對(duì)手,如多標(biāo)簽交換(MPLS),執(zhí)行類似的任務(wù),并可望在未來(lái)取代ATM? </p><p><b>　　電臺(tái)和電視臺(tái) </

54、b></p><p>　　在一個(gè)廣播系統(tǒng),中央高功率廣播塔傳輸高頻率的電磁波 ,到眾多的低功率接收器上?由廣播塔發(fā)送的高頻率波由信號(hào)調(diào)制且該信號(hào)載有視頻或音頻信息?接收天線稍作調(diào)整，以提取高頻率波,解調(diào)器用來(lái)恢復(fù)載有視力或音頻信息的信號(hào)?廣播信號(hào)可以是模擬(信號(hào)多種多樣,載有信息且連續(xù))或數(shù)字(信息作為一套離散值,可以編碼)? </p><p>　　廣播媒體業(yè)正處于發(fā)展中一個(gè)關(guān)鍵的轉(zhuǎn)

55、折點(diǎn),許多國(guó)家都從模擬發(fā)展到數(shù)字廣播?此舉是可使生產(chǎn)更經(jīng)濟(jì),更快且更能夠集成電路 ?與傳統(tǒng)的模擬廣播相比,數(shù)字廣播最大的優(yōu)勢(shì)是,他們防止了一些投訴?對(duì)電視來(lái)說(shuō),這包括消除問題,如雪花屏,重影和其他失真? 這些發(fā)生原因,是因?yàn)槟M傳輸?shù)男再|(zhì),這意味著噪聲干擾會(huì)明顯影響最后的輸出?數(shù)字傳輸,克服了這個(gè)問題,因?yàn)榻邮諘r(shí)數(shù)字信號(hào)變?yōu)殡x散值,這樣小擾動(dòng)不影響最終輸出?舉一個(gè)簡(jiǎn)單的例子,一個(gè)二進(jìn)制信息1011,已與信號(hào)的振幅[ 1.0 0.0 1.

56、0 1.0 ]調(diào)制,并收到信號(hào)的振幅[ 0.9 0.2 1.1 0.9 ]它將仍然解碼為二進(jìn)制信息1011-一個(gè)完美原碼再現(xiàn)?從這個(gè)例子可以看出,數(shù)字傳輸也由一個(gè)問題,如果噪音足夠大,它可以大大改變解碼信息? 使用前向錯(cuò)誤校正接收器可以在最終結(jié)果中糾正少數(shù)比特錯(cuò)誤,但太多的噪音將導(dǎo)致難以理解的輸出,因此,傳輸失敗?</p><p>　　在數(shù)字電視廣播中,有3個(gè)相互競(jìng)爭(zhēng)的標(biāo)準(zhǔn),很可能是全世界公認(rèn)的?它們是ATSC標(biāo)

57、準(zhǔn),DVB標(biāo)準(zhǔn)和ISDB標(biāo)準(zhǔn);通過(guò)這些標(biāo)準(zhǔn),到目前為止,應(yīng)用于標(biāo)題地圖? 所有這三個(gè)標(biāo)準(zhǔn),使用MPEG - 2 視頻壓縮? ATSC標(biāo)準(zhǔn)采用杜比數(shù)字AC - 3音頻壓縮,ISDB利用先進(jìn)音頻編碼 ( MPEG - 2的第7部分),而DVB沒有音頻壓縮標(biāo)準(zhǔn),但通常使用MPEG - 1第3部分第2層 ?不同標(biāo)準(zhǔn)所用的調(diào)制方式也有所不同?在數(shù)字音頻廣播中,標(biāo)準(zhǔn)更為統(tǒng)一,幾乎所有國(guó)家都選擇采用數(shù)字音頻廣播的標(biāo)準(zhǔn)(也稱為作為尤里卡147標(biāo)準(zhǔn))?

58、也有例外,美國(guó)已選擇采用高清廣播?高清廣播,不同于尤里卡147 ,它是基于稱為在帶內(nèi)通道傳輸?shù)膫鬏敺椒?這使數(shù)字化信息,進(jìn)行“背馱式”AM或FM模擬傳輸?</p><p>　　然而,盡管數(shù)字化迫在眉睫,模擬接收機(jī)仍然普遍應(yīng)用? 模擬電視仍然傳送幾乎所有國(guó)家?美國(guó)希望于2006年 12月31日之前結(jié)束模擬廣播;不過(guò),最近又推到2009年 2月17日 ?對(duì)于模擬電視,有三個(gè)標(biāo)準(zhǔn)在使用中?它們是PAL制式 ,NTSC制

59、式和SECAM制式 ? 模擬電臺(tái),切換到數(shù)字變得更加困難,因?yàn)槟M接收器只占數(shù)字接收機(jī)的一小部分成本?模擬電臺(tái)調(diào)制方式通常采用AM(幅度調(diào)制)或FM(頻率調(diào)制)?為實(shí)現(xiàn)立體聲播放 ,振幅調(diào)制副載波用于立體聲調(diào)頻 ? </p><p><b>　　互聯(lián)網(wǎng) </b></p><p>　　互聯(lián)網(wǎng)是一個(gè)全球計(jì)算機(jī)組成的網(wǎng)絡(luò),也是一種用IP聯(lián)系在一起的計(jì)算機(jī)網(wǎng)絡(luò)?在互聯(lián)網(wǎng)上的

60、任何一臺(tái)計(jì)算機(jī)都有一個(gè)唯一的IP地址,其他計(jì)算機(jī)可以用其進(jìn)行路由選擇?因此,在互聯(lián)網(wǎng)上,任何一臺(tái)電腦可以通過(guò)IP地址傳送訊息給任何其他的計(jì)算機(jī)? 這些帶有計(jì)算機(jī)IP地址的信息,允許計(jì)算機(jī)之間雙向溝通?這樣一來(lái),互聯(lián)網(wǎng)可以被看作是一個(gè)計(jì)算機(jī)之間信息的交換?</p><p>　　據(jù)估計(jì),16.9 %的世界人口已經(jīng)進(jìn)入互聯(lián)網(wǎng)且具有最高訪問率(以人口百分比衡量),它們?cè)诒泵赖貐^(qū)(69.7 %),大洋洲/澳大利亞(53.5

61、%)和歐洲(38.9%)?在寬帶接入方面,冰島(26.7%),韓國(guó)(25.4%)和荷蘭(25.3 %)世界領(lǐng)先?</p><p>　　互聯(lián)網(wǎng)的成功,部分是因?yàn)閰f(xié)議管理計(jì)算機(jī)和路由器如何互相溝通? 計(jì)算機(jī)網(wǎng)絡(luò)通信本身的性質(zhì),有助于分層實(shí)現(xiàn),此時(shí),協(xié)議棧中的各個(gè)獨(dú)立協(xié)議或多或少獨(dú)立于其他協(xié)議?這使得低級(jí)別的協(xié)議適應(yīng)網(wǎng)絡(luò)的情況,而不影響高層協(xié)議的實(shí)現(xiàn)?一個(gè)實(shí)際的例子可以說(shuō)明它的重要性,因?yàn)樗试S一個(gè)互聯(lián)網(wǎng)瀏覽器上運(yùn)行相

62、同的代碼，不管運(yùn)行的計(jì)算機(jī)連接到互聯(lián)網(wǎng)是通過(guò)以太網(wǎng)還是通過(guò)Wi - Fi連接?協(xié)議經(jīng)常以其在OSI參考模型中的位置命名,1983年為第一步,也是一次不成功的嘗試,它試圖建立一個(gè)普遍采用的網(wǎng)絡(luò)協(xié)議套件?</p><p>　　對(duì)于互聯(lián)網(wǎng)來(lái)說(shuō),物理介質(zhì)和數(shù)據(jù)鏈路層協(xié)議可以不同的數(shù)倍包遍歷全球? 這是因?yàn)榛ヂ?lián)網(wǎng)對(duì)所用的物理介質(zhì)或數(shù)據(jù)鏈路協(xié)議沒有限制?這導(dǎo)致媒體和協(xié)議的應(yīng)用,它們最適合本地網(wǎng)絡(luò)的情況?在實(shí)踐中,多數(shù)洲際通訊

63、將使用異步轉(zhuǎn)移模式 ( ATM )協(xié)議(或一個(gè)現(xiàn)代的替代物)并輔以光纖? 這是因?yàn)?對(duì)于大多數(shù)的洲際通信來(lái)說(shuō),互聯(lián)網(wǎng)與公共交換式電話網(wǎng)絡(luò)一樣擁有相同的基礎(chǔ)設(shè)施? </p><p>　　在網(wǎng)絡(luò)層,適用于邏輯尋址的IP開始標(biāo)準(zhǔn)化?在萬(wàn)維網(wǎng)上,這些“IP地址”來(lái)自通過(guò)域名系統(tǒng)處理的人類可讀格式(例如72.14.207.99是來(lái)自www.google.com)中?目前,使用最廣泛的版本的互聯(lián)網(wǎng)協(xié)議是版本4 ,但向版本六過(guò)

64、渡已是迫在眉睫?</p><p>　　在傳輸層大部分通信采用的是傳輸控制協(xié)議(TCP)或用戶數(shù)據(jù)報(bào)協(xié)議(UDP)? TCP是基本協(xié)議,每條來(lái)自其他計(jì)算機(jī)的消息均需采用TCP,而UDP只有在有利時(shí)才會(huì)被采用?有了TCP,數(shù)據(jù)包若在它們置于更高層次前丟失或亂序,它們會(huì)被重發(fā)?有了UDP,數(shù)據(jù)包丟失時(shí)會(huì)亂序,也不會(huì)重發(fā)? TCP和UDP數(shù)據(jù)包攜帶端口以便指出數(shù)據(jù)包應(yīng)交由哪些應(yīng)用程序或進(jìn)程?因?yàn)槟承?yīng)用級(jí)協(xié)議使用某些端口

65、 ,網(wǎng)絡(luò)管理員可以通過(guò)阻斷某一特定端口為目的端口的傳輸限制上網(wǎng)?</p><p>　　在傳輸層之上,有一些協(xié)議會(huì)用到并適當(dāng)應(yīng)用于會(huì)話層和表示層,最顯著的是安全套接層(SSL)和傳輸層安全 (TLS)協(xié)議? 這些協(xié)議,確保雙方之間傳輸?shù)臄?shù)據(jù)仍然完全保密并且一方或另一方在使用時(shí),掛鎖出現(xiàn)于Web瀏覽器的底部?最后,在應(yīng)用層,有很多的協(xié)議為互聯(lián)網(wǎng)用戶所熟悉,如HTTP ( Web瀏覽) , 的POP3 (電子郵件),F

66、TP (檔案?jìng)鬏?,IRC (網(wǎng)上聊天),BitTorrent(文件共享)和OSCAR(即時(shí)通訊)? </p><p><b>　　局域網(wǎng) </b></p><p>　　不看互聯(lián)網(wǎng)的發(fā)展, 僅局域網(wǎng)的特點(diǎn) (運(yùn)行于幾公里內(nèi)的計(jì)算機(jī)網(wǎng)絡(luò))仍然明顯?這是因?yàn)檫@種規(guī)模的網(wǎng)絡(luò)并不需要所有與較大的網(wǎng)絡(luò)有關(guān)的功能,因此往往更具成本效益和高效率? </p><p

67、>　　在二十世紀(jì)八十年代中期,幾個(gè)協(xié)議套件的出現(xiàn),填補(bǔ)了OSI參考模型中數(shù)據(jù)鏈路層和應(yīng)用層之間的空隙? 如AppleTalk,IPX和NetBios與20世紀(jì)90年代初占主導(dǎo)地位,因MS-DOS而廣受歡迎的協(xié)議套件IPX? 而TCP / IP,在這一點(diǎn)上,通常只用于大型政府和研究設(shè)施?隨著互聯(lián)網(wǎng)的受歡迎程度的增長(zhǎng)以及較大的流量與互聯(lián)網(wǎng)逐漸相關(guān),局域網(wǎng)逐步走向TCP / IP?今天的網(wǎng)絡(luò)大多用于TCP / IP流量是常見的?向TCP

68、 / IP的轉(zhuǎn)變由如允許的TCP / IP客戶發(fā)現(xiàn)自己的網(wǎng)絡(luò)地址的DHCP的技術(shù)支撐,而這與A ppleTalk,IPX/和N etBIOS協(xié)議套件以其成為標(biāo)準(zhǔn)? </p><p>　　在數(shù)據(jù)鏈路層,最現(xiàn)代的局域網(wǎng)偏離互聯(lián)網(wǎng)?而異步轉(zhuǎn)移模式(ATM)或多協(xié)議標(biāo)簽轉(zhuǎn)換 (MPLS)技術(shù)是典型的數(shù)據(jù)鏈路協(xié)議,適用于較大的網(wǎng)絡(luò)?以太網(wǎng)和令牌環(huán)網(wǎng)是典型的局域網(wǎng)數(shù)據(jù)鏈路協(xié)議?這些協(xié)議不同于前協(xié)議,因?yàn)樗鼈兏?jiǎn)單(例如,它們

69、省略了服務(wù)質(zhì)量保證等功能) ,并提供碰撞預(yù)防?雙方的這些差異,是基于經(jīng)濟(jì)成本的考慮?</p><p>　　盡管令牌環(huán)在80年代和90年代有了一定的普及,但是現(xiàn)在幾乎所有的局域網(wǎng)使用有線或無(wú)線以太網(wǎng)?在物理層,大多數(shù)有線以太網(wǎng)實(shí)現(xiàn)使用銅雙絞線電纜 (包括常用的10 Base-T的網(wǎng)絡(luò))?然而,一些早期的實(shí)現(xiàn)使用同軸電纜,而最近的一些實(shí)現(xiàn)(特別是超高速的)使用光纖?光纖也可能在即將到來(lái)的10千兆以太網(wǎng)的實(shí)現(xiàn)中有著出色