傳輸與交換通信網(wǎng)課件

1、第1章 接入網(wǎng)基礎(chǔ) 1.1 接入網(wǎng)概述1.2 接入網(wǎng)絡(luò)分類與接口協(xié)議1.3 PPP協(xié)議通信網(wǎng): 由終端、主機(jī)、傳輸與交換設(shè)備等組成，采用標(biāo)準(zhǔn)協(xié)議，實(shí)現(xiàn)信息采集與處理、傳輸與交換的網(wǎng)絡(luò)。計(jì)算機(jī)網(wǎng)絡(luò)：用通信線路和設(shè)備將分散在不同地理位置上、具有獨(dú)立功能的多臺(tái)計(jì)算機(jī)系統(tǒng)連接起來，按照網(wǎng)絡(luò)協(xié)議進(jìn)行數(shù)據(jù)通信，實(shí)現(xiàn)資源共享(硬、軟件、數(shù)據(jù))，進(jìn)行合作共享的計(jì)算機(jī)集合。 一、 信息網(wǎng)特點(diǎn)重在計(jì)算機(jī)應(yīng)用、面向用戶 (計(jì)算機(jī)網(wǎng)絡(luò))重在信息采集與處理、傳輸與交換 (通信網(wǎng))信息網(wǎng): 由用戶與網(wǎng)絡(luò)終端、傳輸與交換設(shè)備等組成，采用標(biāo)準(zhǔn)協(xié)議，實(shí)現(xiàn)信息采集與處理、傳輸與交換的網(wǎng)絡(luò)，其實(shí)際形式包括通信網(wǎng)和/或計(jì)算機(jī)網(wǎng)絡(luò)。

2、2. 接入網(wǎng) 實(shí)現(xiàn)不同用戶駐地網(wǎng)或子網(wǎng)級(jí)的匯聚與分發(fā)、用戶信息的集中/分發(fā)，以及內(nèi)部交換，一般由NSP (network service provider)提供；3. 用戶駐地網(wǎng)(CPN/CPE- Customer Premise Network /Equipment) 由用戶駐地(如大學(xué)校園、工廠、辦公大樓、居民住宅小區(qū)等)處的終端、主機(jī)、線路設(shè)備(如接線箱)、傳輸與交換設(shè)備等組成，實(shí)現(xiàn)用戶認(rèn)證及信息的集中/分發(fā)。其典型代表有用戶單位的用戶交換機(jī)(PABX)和計(jì)算機(jī)局域網(wǎng)。 1. 骨干網(wǎng)絡(luò)backbone network，也稱核心網(wǎng)(core network)，實(shí)現(xiàn)信息高速、大容量的傳輸與交

3、換；(傳輸transmission + 交換switching =傳送 transport)； 用戶駐地網(wǎng) 這3種網(wǎng)絡(luò)的2種網(wǎng)絡(luò)邊界(核心網(wǎng)/接入網(wǎng)、接入網(wǎng)/用戶駐地網(wǎng))存在重疊接入網(wǎng)核心網(wǎng)二、信息網(wǎng)間關(guān)系 PSTN: 電信網(wǎng)CN： Computer NetworkBCN：Broadcasting & Cable TV Network)傳送網(wǎng)由三個(gè)網(wǎng)絡(luò)的任兩個(gè)或全部組成的傳送資源PSTNCNBCNInternet應(yīng)用網(wǎng)/業(yè)務(wù)網(wǎng)網(wǎng)絡(luò) 源 宿 傳送資源由同一種網(wǎng)絡(luò)提供；由2種網(wǎng)絡(luò)提供；由3種網(wǎng)絡(luò)提供；三網(wǎng)與因特網(wǎng)是分離的兩個(gè)網(wǎng)，各有自己的業(yè)務(wù)(電話/數(shù)據(jù)/電視，WWW/FTP/E-MAIL)；兩者

4、均可完成數(shù)據(jù)業(yè)務(wù)的傳送，但對(duì)數(shù)據(jù)業(yè)務(wù)支持的層次不同，三網(wǎng)完成IP層及以下的功能，而因特網(wǎng)完成IP及其以上各層的功能；因特網(wǎng)可有自己的物理網(wǎng)絡(luò)，如局域網(wǎng)，更廣大地區(qū)的用戶需通過三網(wǎng)接入因特網(wǎng)；從業(yè)務(wù)角度而言，三網(wǎng)是物理承載(傳送)網(wǎng)絡(luò)，因特網(wǎng)是業(yè)務(wù)(應(yīng)用)網(wǎng)。三、接入網(wǎng)概念1.早期含義 現(xiàn)有網(wǎng)絡(luò)主要從電信網(wǎng)(PSTN)演變發(fā)展而成，接入網(wǎng)的早期形式是：1)本地用戶環(huán)路(Local loop)2)用戶網(wǎng)(Subscriber network)3)用戶環(huán)路系統(tǒng)等。 see the chart on next pageSW- Switch,交換機(jī)RSU- Remote Switch Unit, 遠(yuǎn)端交

5、換單元RT- Remote Termination, 遠(yuǎn)端終結(jié)FP- Flexible Point, DP- Distribution Point CPN/CPE# - Customer Promise Network/Equipments-用戶網(wǎng)2. ITU-T (G.902)定義由用戶網(wǎng)絡(luò)接口(UNI-User Network Interface)和業(yè)務(wù)結(jié)點(diǎn)接口(SNI-Service Node Interface)間的一系列傳送實(shí)體組成(包括線路設(shè)施和交換設(shè)備)，為傳輸電信業(yè)務(wù)提供所需傳送承載能力，可通過Q3接口進(jìn)行配置與管理。(see the chart on next page)接入

6、網(wǎng)組成模型接入網(wǎng)業(yè)務(wù)結(jié)點(diǎn)TMNQ3用戶終端1用戶終端NQ3SNIUNIUNI An implementation comprising those entities which provide the required transport bearer capabilities for the provision of telecommunications services between a Service Node Interface (SNI) and each of the associated User Network Interfaces (UNIs)。2.1 用戶網(wǎng)絡(luò)接口(UNI

7、)在接入網(wǎng)的用戶側(cè)，支持各種業(yè)務(wù)的接入。主要包括：1)模擬電話接口(POTS) Plain Old Telephone System2)ISDN UNI基本速率 2B+D; 基群速率(E1/T1) 30B+D /23B+D3)數(shù)字接口E1，N*64K4)低中速接口RS232/V.24，V.35，RS-449(422A、423A) 5)寬帶接口a) SDH#接口： STM-N N=0，1，4，16，64 STM: Synchronous Transfer Module (同步傳遞模塊) b) USB (Universal Serial Bus) c) GE (Gigabit Ethernet)2

8、.2 業(yè)務(wù)結(jié)點(diǎn)接口(SNI)位于接入網(wǎng)的業(yè)務(wù)側(cè)，為不同的用戶業(yè)務(wù)提供相應(yīng)的業(yè)務(wù)結(jié)點(diǎn)接口，實(shí)現(xiàn)與核心網(wǎng)交換設(shè)備的連接。核心網(wǎng)交換設(shè)備早期主要指電話交換機(jī)，現(xiàn)在則指數(shù)據(jù)傳輸與交換設(shè)備(如路由器)實(shí)際上(現(xiàn)狀是)可包括：現(xiàn)有交換機(jī)/路由器的幾乎所有接口, 如SDH 同步數(shù)字序列/同步數(shù)體系(STM-N, 信元或分組, 在北美稱為同步光聯(lián)網(wǎng)SONETSynchronous Optical Networking), PDH (Plesiosynchronous Digital Hierarchy) 準(zhǔn)同步數(shù)字序列, ATM，Ethernet (FE，GE，10GE)等2.3 Q3接口 TMN (Tele

9、communication Management Networks) 通過Q3實(shí)現(xiàn)對(duì)接入網(wǎng)的管理與協(xié)調(diào)，為用戶提供所需接入類型與承載能力。 如UNI終接(termination)、激活去激活(Activation /Deactivation)、復(fù)用(multiplexing)、通道映射(mapping)、信令處理配置(使用何種信令、信令傳送方式)、用戶端口狀態(tài)等。 四、IP接入網(wǎng) 1. 定義(ITU-T SG13， Y.1231)接入網(wǎng)指在 IP用戶和IP 業(yè)務(wù)提供者之間(Internet Service Provider：ISP)為提供所需的接入到IP業(yè)務(wù)的能力、網(wǎng)絡(luò)實(shí)體的實(shí)現(xiàn)。(圖見紀(jì)P2

10、2) 接入網(wǎng)參考模型 (圖見紀(jì)P22 )用戶駐地網(wǎng)與接入網(wǎng)，接入網(wǎng)與核心網(wǎng)間有參考點(diǎn) G.902與Y.1231的區(qū)別G.902Y.1231模型接口UNI、SNIRP傳輸功能復(fù)用、交叉連接,一般不含交換一般有交換計(jì) 費(fèi)不(計(jì)費(fèi)在核心網(wǎng))需 要接口開放性V5系列 (現(xiàn)在很少用)眾多選擇五、廣義接入網(wǎng) 由用戶(或用戶駐地網(wǎng))和核心網(wǎng)間的傳送實(shí)體組成(包括線路設(shè)施和傳輸交換等設(shè)備)，用戶(駐地網(wǎng))及核心網(wǎng)與 接入網(wǎng)間接口采用開放的標(biāo)準(zhǔn)接口，經(jīng)濟(jì)地為用戶提供所需的傳送能力。(from my viewpoint) ANCNCPE/CPN開放接口 開放接口 遠(yuǎn)端模塊交換機(jī)內(nèi)部標(biāo)準(zhǔn)(如早期Pair gain，

11、電話倍增器) 用戶內(nèi)部標(biāo)準(zhǔn) 1.2 接入網(wǎng)分類與接口協(xié)議 1.1 接入網(wǎng)概述1.2 接入網(wǎng)絡(luò)分類與接口協(xié)議1.3 PPP協(xié)議一、接入網(wǎng)分類 1) 按采用的技術(shù)體制分類(ATM、IP、Ethernet，或幾種技術(shù)的混合)；2) 按應(yīng)用領(lǐng)域分類(民用(家庭、校園、社區(qū)，), 軍用，應(yīng)急等)按傳輸媒質(zhì)的屬性分類(有線、無線、混合)。1. 有線(傳輸)接入 銅線對(duì) xDSL (Digital Subscriber Line)x=Asymmetric，High-speed bit rate, Very high-speed bit rate，ISDN， Rate Adaptive, Symmetric，

12、Ethernet (Ethernet over DSL)， 128k51Mbps 幾百m5km 光纖網(wǎng)絡(luò)(OFN) 主要用于 FTTx (Fiber to the x ， x=B, C, H, ) FTTB (building), FTTC (Curb), FTTH (Home)a) AON (Active Optical Network 有源光網(wǎng)絡(luò))： 可提供電路信號(hào) (如Ei, i=1,2,3,4，E1=2.048M;)和 數(shù)據(jù)業(yè)務(wù)PoS (Packet over SDH)SDH #(Synchronous Digital Hierarchy, 同步數(shù)字系列(體系)，系列：下一等級(jí)速率是前

13、一等級(jí)的4倍) TUG: Tributary Unit Group/支路單元組)STM-N # N=0,1,4,16,64,256 51.84M 40GbpssSTM-2n (s-sub，子) n=1,2,4.(7.488, 14.400, 28.224)MbpssSTM-1k k=1,2,4,8,16 (2.880,5.184, 9.792,19.792, 37.444)MbpssSTM-2n 適用于光纖、雙絞線、無線傳送(TUG-2)sSTM-1k 適用于無線傳送(TU-12)b) 無源光網(wǎng) (xPON, Passive Optical Network, x=E/GE,A,G; Ether

14、net, Gigabit Ethernet, ATM, Gigabit ) ： 由光合成/分配器件等無源器件組成; 例如，APON提供對(duì)稱STM-1, 或上行STM-1/下行STM-4 混合光纖電纜HFC (Hybrid Fiber Coax (Coaxial Cable) 光纖到樓宇或小區(qū)，樓宇或小區(qū)內(nèi)部使用Cable； 可提供模擬電視，數(shù)百用戶可共享1000 Mbps的傳輸寬帶(數(shù)據(jù)接入，Internet) 2. 無線(傳輸)接入 從用戶終端(UNI)到業(yè)務(wù)結(jié)點(diǎn)接口(SNI)間全部或部分采用無線傳輸 固定無線接入覆蓋：50m 幾十km頻率：幾十M幾十GHZ方式：FDMA，TDMA，CDMA

15、；二者的結(jié)合，如MF-TDMA(多頻TDMA) 短波/超短波，PMP點(diǎn)到多點(diǎn)微波系統(tǒng)，直播衛(wèi)星系位DBS，“無線光”視距傳輸 (2431GHZ, 寬帶1G HZ) ，“燈光上網(wǎng)”：無線光通信技術(shù)Lifi在復(fù)旦大學(xué)實(shí)驗(yàn)成功, 遲楠教授，Light+fi (WiFi: Wireless Fidelity), 下行3.7Gbps，上行？移動(dòng)無線接入 第2代無線系統(tǒng)：GSM. IS-95 第3代移動(dòng)通信(3G)：WCDMA(FDD/TDD Frequency/Time division Duplex) ， CDMA2000 (1x/3x), TD-SCDMA (智能信號(hào)處理) UTRAN:UMTS (

16、Universal Mobile Telecommunication System) Terrestrial Radio Access Network，第一階段基于ATM，第二階段IP，第三階段IP多媒體 第4代移動(dòng)通信(4G)：接入網(wǎng)LTE (長(zhǎng)期演進(jìn))3. 混合接入 使用以上各種無線與有線(傳輸)接入技術(shù)的組合。WLAN: 無線LANIEEE802.11(1, 2 Mbps) /11a (6,12,18,24,36,48,54)Mbps /11b(1,2,5.5,11) Mbps / 11g (功能上11a+11b)(與11b兼容, 11g標(biāo)準(zhǔn)在完善) IEEE 802.16,其它(高、中

17、、低軌道，GEO/MEO/LEO, Geostationary Earth Orbit, )衛(wèi)星、藍(lán)牙Bluetooth、高空平臺(tái)、 二、 接入網(wǎng)接口與協(xié)議 1.用戶網(wǎng)絡(luò)接口(UNI) 1)Z接口 是交換機(jī)和模擬用戶線的接口，用以連接話機(jī)、話帶MODEM、直流信令、DTMF/PULSE、振鈴、計(jì)次。(DTMF#: Double Tones Multi- Frequency) 2)U接口 ISDN中NT與交換機(jī)線路終端(LT)間的數(shù)據(jù)接口。T/S接口可連接多達(dá)8個(gè)終端。 3)RS-232接口/V.24 (#) “D”型25pins或9pins插座，15m20k Bauds 。 +3V25V 表示

18、數(shù)據(jù)“0”， 控制線接通 -3V-25V 表示數(shù)據(jù) “1” ， 控制線斷開 4)RS-449/V.36 RS-449規(guī)定接口的機(jī)械、功能、流程(procedural )特性; RS-422-A：平衡傳輸 60m2Mbps; RS-423-A：非平衡傳輸 10m300kbps; 5). RJ-11/45 (4線電話/8線網(wǎng)線) (用于電話(RJ-11)、#Ethernet(RJ-45)連接) 1 TXD+2 TXD-3 RXD+456 RXD-78DTEDTRRTSDCEDSRCTSDTE#: Digital Terminal Equipment DCE#: Dataset Communicat

19、ion Equipment Step1 DTR#: Digital Terminal ReadyStep2 DSR#: Dataset Send ReadyStep3 RTS#: Request TO Send Step4 CTS#: Clear TO Send 6)E1接口(G.703) # 線路編碼：HDB3 速率： 2.048Mbps 阻抗： 120 ohm(平衡)/75 ohm(非平衡) 結(jié)構(gòu)： 非成幀(32個(gè)時(shí)隙的純字節(jié))或成幀framing(CRC-4 有/無可選) 連接器： D15F(120 ohm)，BNC(電視電纜75 ohm) ，也有采用RJ11或RJ45 7)V.35 (

20、同步傳輸接口)# RTS、DTS、DSR、CTS 非平衡 (共同地線) TXD、RXD、 Timing (定時(shí)，時(shí)鐘)平衡方式(2線) 34-pins (8+9+8+9,4排) 或DB 37 (18+19,2排) ，也有設(shè)備廠商自定義，采用DB 26 【3排，(9+9+8)】、DB25，兩排1213) 90m10Mbps (距離帶寬積) 610m64kbps 2. 業(yè)務(wù)結(jié)點(diǎn)接口 (SNI)1) .業(yè)務(wù)結(jié)點(diǎn)指能獨(dú)立地提供某種業(yè)務(wù)的“實(shí)體”，是一種可提供復(fù)用/交換的網(wǎng)元。(定義見陶P34)實(shí)例：電話交換機(jī)、X.25交換機(jī)、幀中繼交換機(jī)、ATM交換機(jī)、router、Ethernet交換機(jī)，視頻/音頻

21、服務(wù)器等。 2) . 業(yè)務(wù)結(jié)點(diǎn)類型a) 僅支持一種接入類型ANSN業(yè)務(wù)1 SNI UNIb) 支持多種接入類型，所有接入類型具有相同的接入承載能力; ANSN業(yè)務(wù)1,2 SNI UNIc) 支持多種接入類型，每種接入類型要求不同的接入承載能力。 ANSN1業(yè)務(wù)1,2 SNI 1,2 UNISN23). 業(yè)務(wù)結(jié)點(diǎn)接口類型(SNI)當(dāng)前實(shí)用的SNI還包括符合廣義接入網(wǎng)中的各種現(xiàn)有網(wǎng)絡(luò)接口，主要包括SDH、GE/10GE、E1等。 1.1 接入網(wǎng)概述1.2 接入網(wǎng)絡(luò)分類與接口協(xié)議1.3 PPP協(xié)議1.3 PPP協(xié)議2022/7/24Dr. Zhanqi XU, National Key Lab on

22、 ISN, Xidian University351. PPP 協(xié)議簡(jiǎn)介 PPP (point to point protocol) 是一種應(yīng)用最廣泛的鏈路協(xié)議(如無線路由器)，它提供多于常見鏈路層協(xié)議的功能。PPP 提供的功能#常見的數(shù)據(jù)鏈路控制(建立、終止、維護(hù)等)(可選的)鏈路配置與鏈路質(zhì)量測(cè)試鏈路數(shù)據(jù)差錯(cuò)檢測(cè)動(dòng)態(tài)的IP地址指派與管理網(wǎng)絡(luò)協(xié)議復(fù)用(傳送多種網(wǎng)絡(luò)層協(xié)議)多種協(xié)商選項(xiàng)(網(wǎng)絡(luò)IP地址、數(shù)據(jù)壓縮、認(rèn)證方式等)2022/7/24Dr. Zhanqi XU, National Key Lab on ISN, Xidian University36PPP 協(xié)議傳輸 PPPIPIPX .

23、ADSL/RS-232SDH, InterfaceOSI LayerApplicationPresentationSessionTransportNetworkData LinkPhysicaldataIP datagramIPX datagramPPP FramePPP FrameSerial LinkAP IAP IIdata問題：因特網(wǎng)協(xié)議參考模型包括幾層？每層的名稱？ TCP,UDPSerial Link2022/7/24Dr. Zhanqi XU, National Key Lab on ISN, Xidian University372. PPP 主要部件PPP 采用如下3種部件以

24、提供下3層“傳送網(wǎng)”連接性: (1) 一種數(shù)據(jù)報(bào)(datagram)在串行鏈路上的封裝方法(encapsulating). PPP采用高級(jí)數(shù)據(jù)鏈路協(xié)議 HDLC (High-Level Data Link Control)做為在WAN串行點(diǎn)到點(diǎn)數(shù)據(jù)鏈路(如早期電話modem撥號(hào))上封裝的基礎(chǔ)。 注解：現(xiàn)在的PPP協(xié)議已不限制在串行線路，可工作在任何傳輸線路(如SDH提供的字節(jié)byte線路)，采用的鏈路協(xié)議也不局限于HDLC，例如PPP over Ethernet (PPPoE)。 (2) 一個(gè)鏈路控制協(xié)議LCP (Link Control Protocol) 用于數(shù)據(jù)鏈路連接的建立、配置和測(cè)試

25、。 2022/7/24Dr. Zhanqi XU, National Key Lab on ISN, Xidian University38 (3) 網(wǎng)絡(luò)控制協(xié)議NCPs (Network Control Protocols) 用于建立與配置不同的網(wǎng)絡(luò)層協(xié)議. PPP 允許同時(shí)使用多個(gè)網(wǎng)絡(luò)協(xié)議，如IP、 網(wǎng)間分組交換IPX (Internetwork Packet Exchange) 和 Appletalk. 2022/7/24Dr. Zhanqi XU, National Key Lab on ISN, Xidian University39 IPCP: IP control protoco

26、l (RFC1332，IETF Request For Comments：請(qǐng)求注解) , negotiation for the parameters of TCP/IP PPP支持的物理層包括：串行比特：電話撥號(hào)網(wǎng)(0比特插入、刪除)字節(jié)信道：例如，SDH(兩個(gè)Flag間的“數(shù)據(jù)”flag采用轉(zhuǎn)義字符變換， 見下頁(yè))2022/7/24Dr. Zhanqi XU, National Key Lab on ISN, Xidian University403. PPP 幀格式線路Bit- or Byte-orientedPPP FrameBit/Octet StuffingFlag0 x7eAdd

27、r0 xffCont.0 x03Protocol16 bitsdataFlag0 x7epaddingFCS16/32bits0 xc0210 x00fdLCPCompressed datagramOctet Stuffing(填塞):0 x7e-0 x7d,0 x5e, 0 x7d-0 x7d,0 x5d在HDLC幀傳輸中，對(duì)于幀addr 到FCS的幀內(nèi)容，有兩種填塞或變換方法處理幀內(nèi)容中可能的“幀標(biāo)志flag ”：(1) 對(duì)于bit 信道，“0”比特插入 (連續(xù)5個(gè)1后加0)(2) 對(duì)于byte 信道，字節(jié)變換法2022/7/24Dr. Zhanqi XU, National Key La

28、b on ISN, Xidian University41協(xié)議域代碼含義Value (Hex)Protocol Type 0 x0021IP(datagrams)0 x002dVJ Compressed TCP Header 0 x002fVJ Uncompressed TCP Header0 x00fdCompressed Datagrams0 x8021IPCP(NCP)0 xc021LCP0 xc023PAP0 xc223CHAPNote: vj-Van Jacobson TCP Header Compression注解：Password Authentication Protocol

29、(PAP) and Challenge Handshake Authentication Protocol (CHAP). 注解：PAP-口令鑒權(quán)協(xié)議，CHAP：(詢問,查詢挑戰(zhàn))握手鑒權(quán)協(xié)議2022/7/24Dr. Zhanqi XU, National Key Lab on ISN, Xidian University424. PPP 狀態(tài)轉(zhuǎn)移圖Dead(Init)EstablishTerminateAuthenticationNetworkSuccessopenedFalseSuccessFalseDataTrans.2022/7/24Dr. Zhanqi XU, National Ke

30、y Lab on ISN, Xidian University434個(gè)階段:鏈路建立與配置協(xié)商發(fā)送LCP幀以建立、配置、測(cè)試鏈路鏈路質(zhì)量確定(可選階段) 在鏈路建立與配置后網(wǎng)絡(luò)層協(xié)議配置與協(xié)商源端發(fā)送NCP幀以選擇和配置網(wǎng)絡(luò)層協(xié)議，選擇(TCP/IP, IPX & Appletalk) 配置，并用選擇的網(wǎng)絡(luò)層協(xié)議傳送分組鏈路終止會(huì)話保持在配置的狀態(tài)，直到用 LCP或 NCP幀終止，或有關(guān)激活定時(shí)器溢出，或用戶終止。2022/7/24Dr. Zhanqi XU, National Key Lab on ISN, Xidian University445. PPP 協(xié)議流程1). 在鏈路建立與配置

31、協(xié)商階段，每個(gè) PPP設(shè)備發(fā)送LCP 分組以實(shí)現(xiàn)之。 LCP分組包括一個(gè)配置選擇域以允許設(shè)備協(xié)商選項(xiàng)(options)，例如， 最大傳送單位長(zhǎng)度MTU (maximum transmission unit), 特定PPP域的壓縮方法，鏈路認(rèn)證協(xié)議等。 在任何網(wǎng)絡(luò)層數(shù)據(jù)報(bào)交換前(例如，IP數(shù)據(jù)報(bào))，必須使用 LCP首先打開鏈路連接以協(xié)商有關(guān)參數(shù)。2022/7/24Dr. Zhanqi XU, National Key Lab on ISN, Xidian University45LCP 幀格式Flag0 x7eAddr0 xffCont.0 x03PPP frameData/paddingLCP

32、0 xc021FCS16/32 bitsFlag0 x7eCode8bitsID8bitsLength16bitsData.Question: is there anybody to know the name of the frame if its control segment equals 0 x03 ?2022/7/24Dr. Zhanqi XU, National Key Lab on ISN, Xidian University46Code: 識(shí)別不同類型的 LCP分組鏈路配置: Configure Req/Ack/Nak/Rej (Nak: Negative acknowledg

33、ment, Rej: reject)鏈路終止: Terminate Req/Ack鏈路維護(hù): Code-Reject, Protocol-reject, Echo Req/Reply, Discard req, etc.2) ID 識(shí)別相同類型(code相同)的幀序號(hào)，以防止錯(cuò)誤操作3) Length整個(gè)PPP分組數(shù)據(jù)長(zhǎng)度 (Code, ID, PPP data)2022/7/24Dr. Zhanqi XU, National Key Lab on ISN, Xidian University47LCP 協(xié)商Host AHost B(1)Configure-request(2)Configur

34、e-reject(3)Configure-request(4)Configure-ack(5)Configure-request(6)Configure-ack2022/7/24Dr. Zhanqi XU, National Key Lab on ISN, Xidian University48在鏈路建立與配置協(xié)商之后，允許LCP進(jìn)行可選的鏈路質(zhì)量確定，測(cè)試鏈路以確定其鏈路質(zhì)量是否好到可承載鏈路層協(xié)議。 2). 另外，在鏈路建立和鑒權(quán)協(xié)議選擇后，客戶或用戶站將被鑒權(quán)；如果使用鑒權(quán)，則需在網(wǎng)絡(luò)層協(xié)議配置開始前完成。LCP可延遲網(wǎng)絡(luò)層協(xié)議信息的發(fā)送，直到鑒權(quán)過程完成。2022/7/24Dr. Zh

35、anqi XU, National Key Lab on ISN, Xidian University493). 網(wǎng)絡(luò)層協(xié)議配置協(xié)商 (可選：如采用鏈路質(zhì)量測(cè)試，就當(dāng)LCP完成鏈路質(zhì)量確定后)采用 NCP可完成網(wǎng)絡(luò)層協(xié)議的配置。PPP設(shè)備可發(fā)送NCP分組以選擇和配置一個(gè)或多個(gè)網(wǎng)絡(luò)層協(xié)議(IP, Novell IPX, AppleTalk)。 在PPP協(xié)議配置完成后，可采用人機(jī)接口命令，查看LCP和NCP的狀態(tài)。4). 鏈路終止 可采用LCP在任何時(shí)刻終止鏈路連接，該行為通?；谟脩粽?qǐng)求，但也可能由于載波丟失或計(jì)時(shí)器溢出而發(fā)生。2022/7/24Dr. Zhanqi XU, National K

36、ey Lab on ISN, Xidian University501. PPP introduction （留作學(xué)習(xí)英語(yǔ)）PPPIPIPX .ADSL/RS-232SDH,InterfaceOSI LayerApplicationPresentationSessionTransportNetworkData LinkPhysicaldataIP datagramIPX datagramPPP FramePPP FrameSerial LinkAP IAP IIdataHow many layers are there in the Internet Reference Model ? And

37、 the name of each layer? PPP-point to point protocolTCP,UDP2022/7/24Dr. Zhanqi XU, National Key Lab on ISN, Xidian University511. PPP introduction WAN connections are controlled by protocols that perform the same basic functions as Layer 2 LAN protocols, such as EthernetIn a WAN environment, in orde

38、r to move data between any two nodes or routers, a data path must be established, and flow control procedures must be in place (adv. 適當(dāng)?shù)?to ensure delivery data - by WAN protocols2022/7/24Dr. Zhanqi XU, National Key Lab on ISN, Xidian University52Most widely used and most popular WAN protocol becaus

39、e it offerscontrol of data link setup(dynamic )assignment and management of IP addressesNetwork protocol multiplexingLink configuration and link quality testingError detectionnegotiation options for capabilities such as network-layer address negotiation and data compression negotiation2022/7/24Dr. Z

40、hanqi XU, National Key Lab on ISN, Xidian University532. PPP ComponentsPPP addresses the problems of Internet connectivity by employing three main components: (1) A method for encapsulating (封裝) datagrams over serial links. PPP uses High-Level Data Link Control (HDLC) as a basis for encapsulating da

41、tagrams over point-to-point links. Comments/Tips：現(xiàn)在的PPP協(xié)議已不限制在串行線路，可工作在任何傳輸線路(如SDH提供的字節(jié)byte線路)，采用的鏈路協(xié)議也不局限于HDLC，例如PPP over Ethernet (PPPoE)。 (2) A Link Control Protocol (LCP) for establishing, configuring, and testing the data-link connection. 2022/7/24Dr. Zhanqi XU, National Key Lab on ISN, Xidian

42、University54 (3) A family of Network Control Protocols (NCPs) for establishing and configuring different network-layer protocols. PPP is designed to allow the simultaneous use of multiple network-layer protocols. Today, PPP supports other protocols besides IP, including Internetwork Packet Exchange

43、(IPX) and Appletalk. As shown in the Figure on next page, PPP uses its NCP component to encapsulate multiple protocols.2022/7/24Dr. Zhanqi XU, National Key Lab on ISN, Xidian University55 IPCP: IP control protocol (RFC1332) , negotiation for the parameters of TCP/IP PPP支持的物理層包括：串行比特：電話撥號(hào)網(wǎng)(0比特插入、刪除)字

44、節(jié)信道：例如，SDH(兩個(gè)Flag間的“數(shù)據(jù)”flag采用轉(zhuǎn)義字符變換，見下頁(yè))2022/7/24Dr. Zhanqi XU, National Key Lab on ISN, Xidian University563. PPP frame formatPPP FrameBit/Octet Stuffing線路Flag0 x7eAddr0 xffCont.0 x03Protocol16 bitsdataFlag0 x7epaddingFCS16/32bits0 xc0210 x00fdLCPCompressed datagramOctet Stuffing(填塞):0 x7e-0 x7d,0

45、x5e, 0 x7d-0 x7d,0 x5d In the HDLC frame transmission , there are two types of the stuffing or translation for the Flag possibly appears in the frame except the start/end flags , bit- or octet- based Stuffing, they use two different types for stuffing. How does the bit-based Stuffing work?2022/7/24D

46、r. Zhanqi XU, National Key Lab on ISN, Xidian University57Protocol FieldValue (Hex)Protocol Type 0 x0021IP(datagrams)0 x002dVJ Compressed TCP/IP 0 x002fVJ Uncompressed TCP/IP0 x00fdCompressed Datagrams0 x8021IPCP(NCP)0 xc021LCP0 xc023PAP0 xc223CHAPNote: vj-Van Jacobson TCP Header Compression2022/7/2

47、4Dr. Zhanqi XU, National Key Lab on ISN, Xidian University584. PPP State DiagramDead(Init)EstablishTerminateAuthenticationNetworkSuccessopenedFalseSuccessFalseDataTrans.2022/7/24Dr. Zhanqi XU, National Key Lab on ISN, Xidian University59PPP State DiagramFour distinct phases:Link est. and config nego

48、tiationsends LCP frames to config and test data linkLink quality determinationlink is est & negotiated (optional phase)Network-layer protocol config & negotiationsource sends NCP frames to choose and config net layer protocols, chosen protocol (TCP/IP, IPX & Appletalk) are configured and packets fro

49、m each protocol are sentLink terminationsession remains configured until LCP or NCP frames are sent to terminate session or an activity timer expires or a user intervenes (干涉/阻止)2022/7/24Dr. Zhanqi XU, National Key Lab on ISN, Xidian University605. PPP Procedures1. In the link establishment and conf

50、iguration negotiation phase, each PPP device sends LCP packets to configure and establish the data link. LCP packets contain a configuration option field that allows devices to negotiate the use of options, such as the maximum transmission unit (MTU), compression of certain PPP fields, and the link

51、authentication protocol. Before any network-layer datagrams (for example, IP) can be exchanged, LCP must first open the connection and negotiate the configuration parameters.2022/7/24Dr. Zhanqi XU, National Key Lab on ISN, Xidian University61PPP ProcedureLCP Frame FormatFlag0 x7eAddr0 xffCont.0 x03P

52、PP frameData/paddingLCP0 xc021FCS16/32 bitsFlag0 x7eCode8bitsID8bitsLength16bitsData.Question: is there anybody to know the name of the frame if its control segment equals 0 x03 ?2022/7/24Dr. Zhanqi XU, National Key Lab on ISN, Xidian University62 PPP ProcedureCode: Identifying the types of differen

53、t LCP packetsLink configuration: Configure Req/Ack/Nak/Rej (Nak: Negative acknowledgment, Rej: reject)Link termination: Terminate Req/AckLink maintenance: Code-Reject, Protocol-reject, Echo Req/Reply, Discard req, etc.2) ID Identifying the sequence number of the same type3) LengthTotal PPP data leng

54、th ( Code, ID, PPP data)2022/7/24Dr. Zhanqi XU, National Key Lab on ISN, Xidian University63 PPP ProcedureLCP NegotiationHost AHost B(1)Configure-request(2)Configure-reject(3)Configure-request(4)Configure-ack(5)Configure-request(6)Configure-ack2022/7/24Dr. Zhanqi XU, National Key Lab on ISN, Xidian

55、University64 PPP ProcedureLCP allows an optional link-quality determination phase following the link establishment and configuration negotiation phase. In the link-quality determination phase, the link is tested to determine whether the link quality is good enough to bring up network-layer protocols

56、. 2. In addition, after the link has been established and the authentication protocol chosen, the client or user workstation can be authenticated. Authentication, if used, takes place before the network-layer protocol configuration phase begins. LCP can delay transmission of network-layer protocol i

57、nformation until this phase is completed.2022/7/24Dr. Zhanqi XU, National Key Lab on ISN, Xidian University65 PPP ProcedureNetwork-layer protocol configuration negotiation When LCP finishes the link-quality determination phase, network-layer protocols can be separately configured by the appropriate

58、NCP and can be brought up and taken down at any time. In this phase, the PPP devices send NCP packets to choose and configure one or more network-layer protocols (such as IP, Novell IPX, and AppleTalk). When PPP is configured, you can check its LCP and NCP states by using the show interfaces command

59、.2022/7/24Dr. Zhanqi XU, National Key Lab on ISN, Xidian University66 PPP Procedure4. Link Termination LCP can terminate the link at any time. This is usually done at the request of a user but can happen because of a physical event, such as the loss of a carrier or a timeout. 2022/7/24Dr. Zhanqi XU,

60、 National Key Lab on ISN, Xidian University676. PPP authentication PPP supports two authentication protocols: Password Authentication Protocol (PAP) and Challenge Handshake Authentication Protocol (CHAP). 注解：PAP-口令鑒權(quán)協(xié)議，CHAP：(詢問,查詢挑戰(zhàn))握手鑒權(quán)協(xié)議The authentication options require that the calling side of t