信息網(wǎng)絡(luò)通信基礎(chǔ)-全文預(yù)覽
【正文】 連接類型 物理結(jié)構(gòu) Physical Structures 14 Data Communications Networking Figure Categories of topology 物理拓?fù)浣Y(jié)構(gòu) 15 Data Communications Networking Figure A fully connected mesh topology (five devices) 優(yōu)點(diǎn) : 1. 專用線路 dedicated links 2. 健壯性 robust 3. 秘密性、安全性privacy/security 4. 故障識(shí)別、排除 fault identification/ isolation 5. 缺點(diǎn)： 6. 安裝復(fù)雜，費(fèi)用離譜 16 Data Communications Networking ? Example The Lucky Ducky Corporation has a fully connected mesh work consisting of eight devices. Calculate the total number or cable links needed and the number of ports for each devices. ? Solution Number of links = n(n1)/2=8(81)/2=28 Number of ports per device = n1 = 81=7 17 Data Communications Networking Figure A star topology connecting four stations A dedicated pointtopoint link only to a central controller, hub 星型拓?fù)溆糜诰钟蚓W(wǎng)中，高速局域網(wǎng)通常用星型拓?fù)浣Y(jié)構(gòu) 18 Data Communications Networking Figure A bus topology connecting three stations Used in early Ether LANs but they are less pupular now. 總線拓?fù)涫嵌帱c(diǎn)配置的 (multipoint)。 健壯性差 (robustness) 引出線 分接頭 19 Data Communications Networking Figure A ring topology connecting six stations 被 IBM引入令牌環(huán)局域網(wǎng)時(shí)曾盛行一時(shí)，目前要求高速局域網(wǎng)，這種拓?fù)浣Y(jié)構(gòu)就不流行了。雖然這樣，但是國(guó)內(nèi)的各種科學(xué)技術(shù)還是在飛速地發(fā)展。當(dāng)時(shí)用作接口機(jī)的Honeywell DDP516型小型機(jī)的內(nèi)存只有 12K。 羅伯茨 。作為 Inter的早期骨干網(wǎng)，ARPA的試驗(yàn)并奠定了 Inter存在和發(fā)展的基礎(chǔ)，較好地解決了異種機(jī)網(wǎng)絡(luò)互聯(lián)的一系列理論和技術(shù)問(wèn)題。 28 Data Communications Networking Chronology of Inter Evolution 29 Data Communications Networking Figure Hierarchical anization of the Inter ISP： Inter Service Provider 30 Data Communications Networking 14 PROTOCOLS AND STANDARDS 協(xié)議和標(biāo)準(zhǔn) In this section, we define two widely used terms: protocols and standards. First, we define protocol, which is synonym
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