第1章 接入网基础 1.1 接入网概述 1.2 接入网络分类与接口协议 1.3 PPP协议 Project Progress 2018/9/22 第1章 接入网基础 1.1 接入网概述 1.2 接入网络分类与接口协议 1.3 PPP协议 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University

一、 信息网 通信网: 由终端、主机、传输与交换设备等组成，采用标 准协议，实现信息采集与处理、传输与交换的网络。 Project Progress 2018/9/22 一、 信息网 通信网: 由终端、主机、传输与交换设备等组成，采用标 准协议，实现信息采集与处理、传输与交换的网络。 计算机网络：用通信线路和设备将分散在不同地理位置上、具有独立功能的多台计算机系统连接起来，按照网络协议进行数据通信，实现资源共享(硬、软件、数据)，进行合作共享的计算机集合。 特点 重在计算机应用、面向用户 (计算机网络) 重在信息采集与处理、传输与交换 (通信网) 信息网: 由用户与网络终端、传输与交换设备等组成，采用标准协议，实现信息采集与处理、传输与交换的网络，其实际形式包括通信网和/或计算机网络。 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University

3. 用户驻地网(CPN/CPE- Customer Premise Network /Equipment) Project Progress 2018/9/22 1. 骨干网络 backbone network，也称核心网(core network)，实现信息高速、大容量的传输与交换； (传输transmission + 交换switching =传送 transport)； 2. 接入网 实现不同用户驻地网或子网级的汇聚与分发、用户信息的集中/分发，以及内部交换，一般由NSP (network service provider)提供； 3. 用户驻地网(CPN/CPE- Customer Premise Network /Equipment) 由用户驻地(如大学校园、工厂、办公大楼、居民住宅小区等)处的终端、主机、线路设备(如接线箱)、传输与交换设备等组成，实现用户认证及信息的集中/分发。其典型代表有用户单位的用户交换机(PABX)和计算机局域网。 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University

这3种网络的2种网络边界(核心网/接入网、接入网/用户驻地网)存在重叠 Project Progress 2018/9/22 这3种网络的2种网络边界(核心网/接入网、接入网/用户驻地网)存在重叠 接入网 核心网 用户驻地网 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University

二、信息网间关系 应用网/业务网 PSTN: 电信网 CN： Computer Network Project Progress 2018/9/22 二、信息网间关系 应用网/业务网 PSTN: 电信网 CN： Computer Network BCN：Broadcasting & Cable TV Network) PSTN CN BCN Internet 网络 源 宿 传送资源 由同一种网络提供； 由2种网络提供； 由3种网络提供； 传送网 由三个网络的任两个或全部组成的传送资源 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University

三网与因特网是分离的两个网，各有自己的业务(电话/数据/电视，WWW/FTP/E-MAIL…)； Project Progress 2018/9/22 三网与因特网是分离的两个网，各有自己的业务(电话/数据/电视，WWW/FTP/E-MAIL…)； 两者均可完成数据业务的传送，但对数据业务支持的层次不同，三网完成IP层及以下的功能，而因特网完成IP及其以上各层的功能； 因特网可有自己的物理网络，如局域网，更广大地区的用户需通过三网接入因特网； 从业务角度而言，三网是物理承载(传送)网络，因特网是业务(应用)网。 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University

三、接入网概念 1. 早期含义 现有网络主要从电信网(PSTN)演变发展而成，接入网的早期形式是： 1)本地用户环路(Local loop) Project Progress 2018/9/22 三、接入网概念 1.  早期含义 现有网络主要从电信网(PSTN)演变发展而成，接入网的早期形式是： 1)本地用户环路(Local loop) 2)用户网(Subscriber network) 3)用户环路系统等。 see the chart on next page (见纪P4，图1-4) Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University

Project Progress 2018/9/22 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University

RSU- Remote Switch Unit, 远端交换单元 RT- Remote Termination, 远端终结 Project Progress 2018/9/22 SW- Switch,交换机 RSU- Remote Switch Unit, 远端交换单元 RT- Remote Termination, 远端终结 FP- Flexible Point, DP- Distribution Point CPN/CPE# - Customer Promise Network/Equipments-用户网 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University

Project Progress 2018/9/22 2.  ITU-T (G.902)定义 由用户网络接口(UNI-User Network Interface)和业务结点接口(SNI-Service Node Interface)间的一系列传送实体组成(包括线路设施和交换设备)，为传输电信业务提供所需传送承载能力，可通过Q3接口进行配置与管理。 (see the chart on next page) Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University

Project Progress 2018/9/22 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)。 接入网组成模型 接入网 业务结点 TMN Q3 用户终端1 用户终端N SNI UNI Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University

2.1 用户网络接口(UNI) 在接入网的用户侧，支持各种业务的接入。 主要包括： Project Progress 2018/9/22 2.1 用户网络接口(UNI) 在接入网的用户侧，支持各种业务的接入。 主要包括： 1)模拟电话接口(POTS) Plain Old Telephone System 2)ISDN UNI 基本速率 2B+D; 基群速率(E1/T1) 30B+D /23B+D 3)数字接口 E1，N*64K 4)低中速接口 RS232/V.24，V.35，RS-449(422A、423A) 5)宽带接口 SDH#接口： STM-N N=0，1，4，16，64… STM: Synchronous Transfer Module (同步传递模块), USB (Universal Serial Bus), GE (Gigabit Ethernet) Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University

2.2 业务结点接口(SNI) 位于接入网的业务侧，为不同的用户业务提供相应的 业务结点接口，实现与核心网交换设备的连接。 Project Progress 2018/9/22 2.2 业务结点接口(SNI) 位于接入网的业务侧，为不同的用户业务提供相应的 业务结点接口，实现与核心网交换设备的连接。 核心网交换设备早期主要指电话交换机，现在则指数据 传输与交换设备(如路由器) 实际上(现状是)可包括：现有交换机/路由器的几乎所有 接口, 如SDH 同步数字序列/同步数体系(STM-N, 信元或 分组, 在北美称为同步光联网SONET－Synchronous Optical Networking), PDH (Plesiosynchronous Digital Hierarchy) 准同步数字序列, ATM，Ethernet (FE，GE， 10GE)等 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University

Project Progress 2018/9/22 2.3 Q3接口 TMN (Telecommunication Management Networks) 通过Q3实现对接入网的管理与协调，为用户提供所需接入类型与承载能力。 如UNI终接(termination)、激活／去激活(Activation /Deactivation)、复用(multiplexing)、通道映射(mapping)、信令处理配置(使用何种信令、信令传送方式)、用户端口状态等。 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University

四、IP接入网 1. 定义(ITU-T SG13， Y.1231) Project Progress 2018/9/22 四、IP接入网 1. 定义(ITU-T SG13， Y.1231) 接入网指在 IP用户和IP 业务提供者之间(Internet Service Provider：ISP)为提供所需的接入到IP业务的能力、网络实体的实现。(图见纪P22) Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University

(图见纪P22 )用户驻地网与接入网，接入网与核心网间有参考点 Project Progress 2018/9/22 接入网参考模型 (图见纪P22 )用户驻地网与接入网，接入网与核心网间有参考点 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University

G.902与Y.1231的区别 G.902 Y.1231 模型接口 UNI、SNI RP 传输功能 复用、交叉连接,一般不含交换 一般有交换 Project Progress 2018/9/22 G.902与Y.1231的区别 G.902 Y.1231 模型接口 UNI、SNI RP 传输功能 复用、交叉连接,一般不含交换 一般有交换 计 费 不(计费在核心网) 需 要 接口开放性 V5系列 (现在很少用) 众多选择 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University

Project Progress 2018/9/22 五、广义接入网 由用户(或用户驻地网)和核心网间的传送实体组成(包括线路设施和传输交换等设备)，用户(驻地网)及核心网与 接入网间接口采用开放的标准接口，经济地为用户提供所需的传送能力。(from my viewpoint) AN CN CPE/ CPN 开放接口 用户 远端模块 交换机 内部标准 内部标准 (如早期Pair gain) Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University

1.2 接入网分类与接口协议 1.1 接入网概述 1.2 接入网络分类与接口协议 1.3 PPP协议 Project Progress 2018/9/22 1.2 接入网分类与接口协议 1.1 接入网概述 1.2 接入网络分类与接口协议 1.3 PPP协议 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University

一、接入网分类 1) 按采用的技术体制分类(ATM、IP、Ethernet，或几种技术的混合)； Project Progress 2018/9/22 一、接入网分类 1) 按采用的技术体制分类(ATM、IP、Ethernet，或几种技术的混合)； 2) 按应用领域分类(民用(家庭、校园、社区，…), 军用，应急等) 按传输媒质的属性分类(有线、无线、混合) 。。。 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University

铜线对 xDSL (Digital Subscriber Line) x=Asymmetric，High-speed bit rate, Project Progress 2018/9/22 1. 有线(传输)接入 铜线对 xDSL (Digital Subscriber Line) x=Asymmetric，High-speed bit rate, Very high-speed bit rate，ISDN， Rate Adaptive, Symmetric，Ethernet (Ethernet over DSL)，… 128k~51Mbps 几百m~5km 光纤网络(OFN) 主要用于 FTTx (Fiber to the x ， x=B,C,H,…) FTTB (building), FTTC (Curb), FTTH (Home) Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University

a) AON (Active Optical Network 有源光网络)： Project Progress 2018/9/22 a) AON (Active Optical Network 有源光网络)： 可提供电路信号 (如Ei, i=1,2,3,4，E1=2.048M;)和 数据业务PoS (Packet over SDH) SDH #(Synchronous Digital Hierarchy, 同步数字系列(体系)，系列：下一等级速率是前一等级的4倍) TUG: Tributary Unit Group/支路单元组) STM-N # N=0,1,4,16,64,256 51.84M ~ 40Gbps sSTM-2n (s-sub) n=1,2,4. (7.488, 14.400, 28.224)Mbps sSTM-1k k=1,2,4,8,16 (2.880,5.184, 9.792,19.792, 37.444)Mbps sSTM-2n 适用于光纤、双绞线、无线传送(TUG-2) sSTM-1k 适用于无线传送(TU-12) Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University

由光合成/分配器件等无源器件组成; 例如，APON提供对称STM-1, 或上行STM-1/下行STM-4 Project Progress 2018/9/22 b) 无源光网 (xPON, Passive Optical Network, x=E/GE,A,G; Ethernet, Gigabit Ethernet, ATM, Gigabit ) ： 由光合成/分配器件等无源器件组成; 例如，APON提供对称STM-1, 或上行STM-1/下行STM-4 混合光纤电缆HFC (Hybrid Fiber Coax (Coaxial Cable) 光纤到楼宇或小区，楼宇或小区内部使用Cable； 可提供模拟电视，数百用户可共享1000 Mbps的传输宽带(数据接入，Internet) Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University

从用户终端(UNI)到业务结点接口(SNI)间全部或部分采用无线传输 Project Progress 2018/9/22 2. 无线(传输)接入 从用户终端(UNI)到业务结点接口(SNI)间全部或部分采用无线传输 固定无线接入 覆盖：50m ~ 几十km 频率：几十M~几十GHZ 方式：FDMA，TDMA，CDMA；二者的结合，如MF-TDMA(多频TDMA) 短波/超短波，PMP点到多点微波系统，直播卫星系位DBS，“无线光”视距传输 (24~31GHZ, 宽带1G HZ) ，“灯光上网”：无线光通信技术Lifi在复旦大学实验成功, 迟楠教授，Light+fi (WiFi: Wireless Fidelity), 下行3.7Gbps，上行？ Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University

第一阶段基于ATM(完成)，第二阶段IP(完成)，第三阶段IP多媒体(完成) Project Progress 2018/9/22 移动无线接入 第2代无线系统：GSM. IS-95 第3代移动通信(3G)：WCDMA(FDD/TDD Frequency/Time division Duplex) ， CDMA2000 (1x/3x), TD-SCDMA (智能信号处理) UTRAN:UMTS (Universal Mobile Telecommunication System) Terrestrial Radio Access Network 第一阶段基于ATM(完成)，第二阶段IP(完成)，第三阶段IP多媒体(完成) Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University

使用以上各种无线与有线(传输)接入技术的组合。 Project Progress 2018/9/22 WLAN: 无线LAN IEEE802.11(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)(与11b兼容, 11g标准在完善) IEEE 802.16,… 其它 (高、中、低轨道，GEO/MEO/LEO, Geostationary Earth Orbit, )卫星、蓝牙Bluetooth、高空平台、… 3. 混合接入 使用以上各种无线与有线(传输)接入技术的组合。 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University

二、 接入网接口与协议 1.用户网络接口(UNI) 1)．Z接口 Project Progress 2018/9/22 二、 接入网接口与协议 1.用户网络接口(UNI) 1)．Z接口 是交换机和模拟用户线的接口，用以连接话机、话带MODEM、直流信令、DTMF/PULSE、振铃、计次。(DTMF#: Double Tones Multi- Frequency) 2)．U接口 ISDN中NT与交换机线路终端(LT)间的数据接口。T/S接口可连接多达8个终端。 3)．RS-232接口/V.24 (#) “D”型25pins或9pins插座，15m×20k Bauds 。 +3V~25V 表示数据“0” 控制线接通； -3V~-25V 表示数据“1” 控制线断开 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University

RS-449规定接口的机械、功能、流程(procedural )特性; RS-422-A：平衡传输 60m×2Mbps; Project Progress 2018/9/22 DTE DTR RTS DCE DSR CTS DTE#: Digital Terminal Equipment DCE#: Dataset Communication Equipment Step1 DTR#: Digital Terminal Ready Step2 DSR#: Dataset Send Ready Step3 RTS#: Request TO Send Step4 CTS#: Clear TO Send 4)．RS-449/V.36 RS-449规定接口的机械、功能、流程(procedural )特性; RS-422-A：平衡传输 60m×2Mbps; RS-423-A：非平衡传输 10m×300kbps; 1 TXD+ 2 TXD- 3 RXD+ 4 5 6 RXD- 7 8 5). RJ-11/45 (4线电话/8线网线) (用于电话(RJ-11)、#Ethernet(RJ-45)连接) Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University

6)．E1接口(G.703) # 线路编码：HDB3 速率： 2.048kbps 阻抗： 120 ohm(平衡)/75 ohm(非平衡) Project Progress 6)．E1接口(G.703) # 线路编码：HDB3 速率： 2.048kbps 阻抗： 120 ohm(平衡)/75 ohm(非平衡) 结构： 非成帧(32个时隙的纯字节) 或成帧framing(CRC-4 有/无可选) 连接器： D15F(120 ohm)，BNC(电视电缆75 ohm) ，也有采用RJ11或RJ45 2018/9/22 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University

RTS、DTS、DSR、CTS 非平衡 (共同地线) Project Progress 2018/9/22 7)．V.35 (同步传输接口)# RTS、DTS、DSR、CTS 非平衡 (共同地线) TXD、RXD、 Timing (定时，时钟)平衡方式(2线)  34-pins (8+9+8+9,4排) 或DB 37 (18+19,2排) ，也有设备厂商自定义，采用DB 26 【3排，(9+9+8)】、DB25，两排8＋9) 90m×10Mbps (距离带宽积)～ 610m×64kbps Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University

指能独立地提供某种业务的“实体”，是一种可提供复用/交换的网元。(定义见陶P34) Project Progress 2018/9/22 2. 业务结点接口 (SNI) 1) .业务结点 指能独立地提供某种业务的“实体”，是一种可提供复用/交换的网元。(定义见陶P34) 实例：电话交换机、X.25交换机、帧中继交换机、ATM交换机、router、Ethernet交换机，视频/音频服务器等。 2) . 业务结点类型 a) 仅支持一种接入类型 AN SN 业务1 SNI UNI Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University

b) 支持多种接入类型，所有接入类型具有相同的接入承载能力; Project Progress 2018/9/22 b) 支持多种接入类型，所有接入类型具有相同的接入承载能力; 业务1,2 SNI UNI AN SN c) 支持多种接入类型，每种接入类型要求不同的接入承载能力。 业务1,2 SNI 1,2 UNI SN1 AN SN2 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University

3). 业务结点接口类型(SNI) ＃＃当前实用的SNI还包括符合广义接入网中的各种现有网络接口，主要包括SDH、GE/10GE、E1等。 Project Progress 2018/9/22 3). 业务结点接口类型(SNI) ＃＃当前实用的SNI还包括符合广义接入网中的各种现有网络接口，主要包括SDH、GE/10GE、E1等。 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University

1.3 PPP协议 1.1 接入网概述 1.2 接入网络分类与接口协议 1.3 PPP协议 Project Progress 2018/9/22 1.3 PPP协议 1.1 接入网概述 1.2 接入网络分类与接口协议 1.3 PPP协议 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University

Dr. Zhanqi XU, National Key Lab on ISN, Xidian University New Technoloies of Broadband Access Network Project Progress 2018/9/22 2018/9/22 1. PPP 协议简介 PPP (point to point protocol) 是一种应用最广泛的链路协议(如无线路由器)，它提供多于常见链路层协议的功能。 PPP 提供的功能# 常见的数据链路控制(建立、终止、维护等) (可选的)链路配置与链路质量测试 链路数据查错检测 动态的IP地址指派与管理 网络协议复用(传送多种网络层协议) 多种协商选项(网络IP地址、数据压缩、认证方式等) 35 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University 35

Dr. Zhanqi XU, National Key Lab on ISN, Xidian University New Technoloies of Broadband Access Network Project Progress 2018/9/22 2018/9/22 PPP 协议传输 OSI Layer AP I AP II Application Presentation Session Transport data data TCP,UDP IP datagram IPX datagram Network IP IPX .. Data Link PPP PPP Frame PPP Frame Physical ADSL/RS-232 SDH, Interface Serial Link Serial Link 问题：因特网协议参考模型包括几层？每层的名称？ 36 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University 36

Dr. Zhanqi XU, National Key Lab on ISN, Xidian University New Technoloies of Broadband Access Network Project Progress 2018/9/22 2018/9/22 2. PPP 主要部件 PPP 采用如下3种部件以提供下3层“传送网”连接性: (1) 一种数据报(datagram)在串行链路上的封装方法(encapsulating). PPP采用高级数据链路协议 HDLC (High-Level Data Link Control)做为在WAN串行点到点数据链路(如早期电话modem拨号)上封装的基础。 注解：现在的PPP协议已不限制在串行线路，可工作在任何传输线路(如SDH提供的字节byte线路)，采用的链路协议也不局限于HDLC，例如PPP over Ethernet (PPPoE)。 (2) 一个链路控制协议LCP (Link Control Protocol) 用于数据链路连接的建立、配置和测试。 37 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University 37

Dr. Zhanqi XU, National Key Lab on ISN, Xidian University Project Progress New Technoloies of Broadband Access Network 2018/9/22 2018/9/22 (3) 网络控制协议NCPs (Network Control Protocols) 用于建立与配置不同的网络层协议. PPP 允许同时使用多个网络协议，如IP、 网间分组交换IPX (Internetwork Packet Exchange) 和 Appletalk. 38 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University 38

Dr. Zhanqi XU, National Key Lab on ISN, Xidian University Project Progress New Technoloies of Broadband Access Network 2018/9/22 2018/9/22 IPCP: IP control protocol (RFC1332，IETF Request For Comments：请求注解) , negotiation for the parameters of TCP/IP PPP支持的物理层包括： 串行比特：电话拨号网(0比特插入、删除) 字节信道：例如，SDH(两个Flag间的“数据”flag采用转义字符变换， 见下页) 39 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University 39

Dr. Zhanqi XU, National Key Lab on ISN, Xidian University Project Progress New Technoloies of Broadband Access Network 2018/9/22 2018/9/22 3. PPP 帧格式 PPP Frame Bit/Octet Stuffing Flag 0x7e Addr 0xff Cont. 0x03 Protocol 16 bits data padding FCS 16/32bits 0xc021 0x00fd LCP Compressed datagram 线路 Bit- or Byte-oriented Octet Stuffing(填塞):0x7e-0x7d,0x5e, 0x7d-0x7d,0x5d 在HDLC帧传输中，对于帧addr 到FCS的帧内容，有两种填塞或变换方法处理帧内容中可能的“帧标志flag ”： (1) 对于bit 信道，“0”比特插入 (连续5个1后加0) (2) 对于byte 信道，字节变换法 40 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University 40

Dr. Zhanqi XU, National Key Lab on ISN, Xidian University Project Progress New Technoloies of Broadband Access Network 2018/9/22 2018/9/22 协议域代码含义 Value (Hex) Protocol Type 注解：Password Authentication Protocol (PAP) and Challenge Handshake Authentication Protocol (CHAP). 注解：PAP-口令鉴权协议，CHAP：(询问,查询挑战)握手鉴权协议 0x0021 IP (datagrams) 0x002d VJ Compressed TCP Header 0x002f VJ Uncompressed TCP Header 0x00fd Compressed Datagrams 0x8021 IPCP (NCP) 0xc021 LCP 0xc023 PAP 0xc223 CHAP Note: vj-Van Jacobson TCP Header Compression 41 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University 41

Dr. Zhanqi XU, National Key Lab on ISN, Xidian University Project Progress New Technoloies of Broadband Access Network 2018/9/22 2018/9/22 4. PPP 状态转移图 opened Establish Authentication Success False Dead(Init) False Success Data Trans. Terminate Network 42 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University 42

Dr. Zhanqi XU, National Key Lab on ISN, Xidian University Project Progress New Technoloies of Broadband Access Network 2018/9/22 2018/9/22 4个阶段: 链路建立与配置协商 发送LCP帧以建立、配置、测试链路 链路质量确定 (可选阶段) 在链路建立与配置后 网络层协议配置与协商 源端发送NCP帧以选择和配置网络层协议，选择(TCP/IP, IPX & Appletalk) 配置，并用选择的网络层协议传送分组 链路终止 会话保持在配置的状态，直到用 LCP或 NCP帧终止，或有关激活定时器溢出，或用户终止。 43 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University 43

Dr. Zhanqi XU, National Key Lab on ISN, Xidian University New Technoloies of Broadband Access Network Project Progress 2018/9/22 2018/9/22 5. PPP 协议流程 1). 在链路建立与配置协商阶段，每个 PPP设备发送LCP 分组以实现之。 LCP分组包括一个配置选择域以允许设备协商选项(options)，例如， 最大传送单位长度MTU＃ (maximum transmission unit), 特定PPP域的压缩方法，链路认证协议等。 在任何网络层数据报交换前(例如，IP数据报)，必须使用 LCP首先打开链路连接以协商有关参数。 44 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University 44

Dr. Zhanqi XU, National Key Lab on ISN, Xidian University Project Progress New Technoloies of Broadband Access Network 2018/9/22 2018/9/22 LCP 帧格式 Code 8bits ID 8bits Length 16bits Data…. Unnumbered Information Flag 0x7e Addr 0xff Cont. 0x03 LCP 0xc021 PPP frame Data/padding FCS 16/32 bits Flag 0x7e Question: is there anybody to know the name of the frame if its control segment equals 0x03 ? 45 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University 45

Dr. Zhanqi XU, National Key Lab on ISN, Xidian University Project Progress New Technoloies of Broadband Access Network 2018/9/22 2018/9/22 Code: 识别不同类型的 LCP分组 链路配置: Configure Req/Ack/Nak/Rej (Nak: Negative acknowledgment, Rej: reject) 链路终止: Terminate Req/Ack 链路维护: Code-Reject, Protocol-reject, Echo Req/Reply, Discard req, etc. 2) ID 识别相同类型(code相同)的帧序号，以防止错误操作 3) Length 整个PPP分组数据长度 (Code, ID, PPP data) 46 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University 46

Dr. Zhanqi XU, National Key Lab on ISN, Xidian University Project Progress New Technoloies of Broadband Access Network 2018/9/22 2018/9/22 LCP 协商 Host A Host B (1)Configure-request (2)Configure-reject (3)Configure-request (4)Configure-ack (5)Configure-request (6)Configure-ack 47 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University 47

Dr. Zhanqi XU, National Key Lab on ISN, Xidian University New Technoloies of Broadband Access Network Project Progress 2018/9/22 2018/9/22 在链路建立与配置协商之后，允许LCP进行可选的链路质量确定，测试链路以确定其链路质量是否好到可承载链路层协议。 2). 另外，在链路建立和鉴权协议选择后，客户或用户站将被鉴权；如果使用鉴权，则需在网络层协议配置开始前完成。LCP可延迟网络层协议信息的发送，直到鉴权过程完成。 48 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University 48

Dr. Zhanqi XU, National Key Lab on ISN, Xidian University New Technoloies of Broadband Access Network Project Progress 2018/9/22 2018/9/22 3). 网络层协议配置协商 (可选：如采用链路质量测试，就当LCP完成链路质量确定后)采用 NCP可完成网络层协议的配置。 PPP设备可发送NCP分组以选择和配置一个或多个网络层协议(IP, Novell IPX, AppleTalk)。 在PPP协议配置完成后，可采用人机接口命令，查看LCP和NCP的状态。 4). 链路终止 可采用LCP在任何时刻终止链路连接，该行为通常基于用户请求，但也可能由于载波丢失或计时器溢出而发生。 49 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University 49

1. PPP introduction （留作学习英语） New Technoloies of Broadband Access Network Project Progress 2018/9/22 2018/9/22 1. PPP introduction （留作学习英语） PPP-point to point protocol OSI Layer AP I AP II Application Presentation Session Transport data data TCP,UDP IP datagram IPX datagram Network IP IPX .. Data Link PPP PPP Frame PPP Frame Physical ADSL/RS-232 SDH,Interface Serial Link How many layers are there in the Internet Reference Model ? And the name of each layer? 50 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University 50

Dr. Zhanqi XU, National Key Lab on ISN, Xidian University New Technoloies of Broadband Access Network Project Progress 2018/9/22 2018/9/22 1. PPP introduction WAN connections are controlled by protocols that perform the same basic functions as Layer 2 LAN protocols, such as Ethernet In a WAN environment, in order to move data between any two nodes or routers, a data path must be established, and flow control procedures must be in place (adv. 适当地)to ensure delivery data -- by WAN protocols 51 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University 51

Dr. Zhanqi XU, National Key Lab on ISN, Xidian University Project Progress New Technoloies of Broadband Access Network 2018/9/22 2018/9/22 Most widely used and most popular WAN protocol because it offers control of data link setup (dynamic )assignment and management of IP addresses Network protocol multiplexing Link configuration and link quality testing Error detection negotiation options for capabilities such as network-layer address negotiation and data compression negotiation 52 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University 52

Dr. Zhanqi XU, National Key Lab on ISN, Xidian University New Technoloies of Broadband Access Network Project Progress 2018/9/22 2018/9/22 2. PPP Components PPP addresses the problems of Internet connectivity by employing three main components: (1) A method for encapsulating (封装) datagrams over serial links. PPP uses High-Level Data Link Control (HDLC) as a basis for encapsulating datagrams over point-to-point links. Comments/Tips：现在的PPP协议已不限制在串行线路，可工作在任何传输线路(如SDH提供的字节byte线路)，采用的链路协议也不局限于HDLC，例如PPP over Ethernet (PPPoE)。 (2) A Link Control Protocol (LCP) for establishing, configuring, and testing the data-link connection. 53 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University 53

Dr. Zhanqi XU, National Key Lab on ISN, Xidian University Project Progress New Technoloies of Broadband Access Network 2018/9/22 2018/9/22 (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 (IPX) and Appletalk. As shown in the Figure on next page, PPP uses its NCP component to encapsulate multiple protocols. 54 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University 54

Dr. Zhanqi XU, National Key Lab on ISN, Xidian University Project Progress New Technoloies of Broadband Access Network 2018/9/22 2018/9/22 IPCP: IP control protocol (RFC1332) , negotiation for the parameters of TCP/IP PPP支持的物理层包括： 串行比特：电话拨号网(0比特插入、删除) 字节信道：例如，SDH(两个Flag间的“数据”flag采用转义字符变换，见下页) 55 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University 55

Dr. Zhanqi XU, National Key Lab on ISN, Xidian University Project Progress New Technoloies of Broadband Access Network 2018/9/22 2018/9/22 3. PPP frame format Flag 0x7e Addr 0xff Cont. 0x03 Protocol 16 bits data LCP Compressed datagram 0xc021 0x00fd padding FCS 16/32bits Flag 0x7e Bit/Octet Stuffing PPP Frame 线路 Octet Stuffing(填塞):0x7e-0x7d,0x5e, 0x7d-0x7d,0x5d 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? 56 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University 56

Dr. Zhanqi XU, National Key Lab on ISN, Xidian University Project Progress New Technoloies of Broadband Access Network 2018/9/22 2018/9/22 Protocol Field Value (Hex) Protocol Type 0x0021 IP (datagrams) 0x002d VJ Compressed TCP/IP 0x002f VJ Uncompressed TCP/IP 0x00fd Compressed Datagrams 0x8021 IPCP (NCP) 0xc021 LCP 0xc023 PAP 0xc223 CHAP Note: vj-Van Jacobson TCP Header Compression 57 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University 57

Dr. Zhanqi XU, National Key Lab on ISN, Xidian University Project Progress New Technoloies of Broadband Access Network 2018/9/22 2018/9/22 4. PPP State Diagram Establish opened Success Authentication False Dead(Init) False Success Data Trans. Terminate Network 58 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University 58

Dr. Zhanqi XU, National Key Lab on ISN, Xidian University New Technoloies of Broadband Access Network Project Progress 2018/9/22 2018/9/22 PPP State Diagram Four distinct phases: Link est. and config negotiation sends LCP frames to config and test data link Link quality determination link is est & negotiated (optional phase) Network-layer protocol config & negotiation source sends NCP frames to choose and config net layer protocols, chosen protocol (TCP/IP, IPX & Appletalk) are configured and packets from each protocol are sent Link termination session 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) 59 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University 59

Dr. Zhanqi XU, National Key Lab on ISN, Xidian University New Technoloies of Broadband Access Network Project Progress 2018/9/22 2018/9/22 5. PPP Procedures 1. In the link establishment and configuration 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 authentication protocol. Before any network-layer datagrams (for example, IP) can be exchanged, LCP must first open the connection and negotiate the configuration parameters. 60 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University 60

Dr. Zhanqi XU, National Key Lab on ISN, Xidian University Project Progress New Technoloies of Broadband Access Network 2018/9/22 2018/9/22 PPP Procedure LCP Frame Format Code 8bits ID 8bits Length 16bits Data…. Unnumbered Information Flag 0x7e Addr 0xff Cont. 0x03 LCP 0xc021 PPP frame Data/padding FCS 16/32 bits Flag 0x7e Question: is there anybody to know the name of the frame if its control segment equals 0x03 ? 61 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University 61

Dr. Zhanqi XU, National Key Lab on ISN, Xidian University New Technoloies of Broadband Access Network Project Progress 2018/9/22 2018/9/22 PPP Procedure Code: Identifying the types of different LCP packets Link configuration: Configure Req/Ack/Nak/Rej (Nak: Negative acknowledgment, Rej: reject) Link termination: Terminate Req/Ack Link maintenance: Code-Reject, Protocol-reject, Echo Req/Reply, Discard req, etc. 2) ID Identifying the sequence number of the same type 3) Length Total PPP data length ( Code, ID, PPP data) 62 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University 62

Dr. Zhanqi XU, National Key Lab on ISN, Xidian University Project Progress New Technoloies of Broadband Access Network 2018/9/22 2018/9/22 PPP Procedure LCP Negotiation Host A Host B (1)Configure-request (2)Configure-reject (3)Configure-request (4)Configure-ack (5)Configure-request (6)Configure-ack 63 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University 63

Dr. Zhanqi XU, National Key Lab on ISN, Xidian University New Technoloies of Broadband Access Network Project Progress 2018/9/22 2018/9/22 PPP Procedure LCP 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. 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 information until this phase is completed. 64 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University 64

Dr. Zhanqi XU, National Key Lab on ISN, Xidian University New Technoloies of Broadband Access Network Project Progress 2018/9/22 2018/9/22 PPP Procedure Network-layer protocol configuration negotiation When LCP finishes the link-quality determination phase, network-layer protocols can be separately configured by the appropriate 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. 65 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University 65

Dr. Zhanqi XU, National Key Lab on ISN, Xidian University New Technoloies of Broadband Access Network Project Progress 2018/9/22 2018/9/22 PPP Procedure 4. 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. 66 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University 66

Dr. Zhanqi XU, National Key Lab on ISN, Xidian University New Technoloies of Broadband Access Network Project Progress 2018/9/22 2018/9/22 6. PPP authentication PPP supports two authentication protocols: Password Authentication Protocol (PAP) and Challenge Handshake Authentication Protocol (CHAP). 注解：PAP-口令鉴权协议，CHAP：(询问,查询挑战)握手鉴权协议 The authentication options require that the calling side of the link enter authentication information to help ensure that the user has the network administrator's permission to make the call. Peer routers exchange authentication messages. 67 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22 Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University Dr. Zhanqi XU,Natioanal Key Lab on ISN,Xidian University 67

Dr. Zhanqi XU, National Key Lab on ISN, Xidian University PPP authentication When configuring PPP authentication, you can select Password Authentication Protocol (PAP) or Challenge Handshake Authentication Protocol (CHAP). In general, CHAP is the preferred protocol. Using a two-way handshake, after the PPP link establishment phase is complete, a username/password pair is repeatedly sent by the remote node across the link until authentication is acknowledged or the connection is terminated. PAP is not a strong authentication protocol. Passwords are sent across the link in clear text, and there is no protection from playback or repeated trial-and-error attacks. 68 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22

Dr. Zhanqi XU, National Key Lab on ISN, Xidian University CHAP CHAP is used to periodically verify the identity of the remote node, using a three-way handshake. This is done upon initial link establishment and can be repeated any time after the link has been established. CHAP offers features such as periodic verification to improve security; this makes CHAP more effective than PAP. CHAP does not allow a caller to attempt authentication without a challenge. After the PPP link establishment phase is complete, the host sends a challenge message to the remote node. The remote node responds with a value. The host checks the response against its own value. If the values match, the authentication is acknowledged. Otherwise, the connection is terminated. (动态、实时鉴权) 69 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22

Dr. Zhanqi XU, National Key Lab on ISN, Xidian University CHAP CHAP provides protection against playback attacks through the use of a variable challenge value that is unique and unpredictable. The use of repeated challenges is intended to limit the time of exposure to any single attack. (exposure: 暴露,曝光) 70 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22

CHAP Handshake Diagram Host A authenticator Host B peer (1)Authentication request -CHAP (2)Authentication Ack (3)challenge,name: Host A and challenge string (4)response ,name: Host B and Resp. String (5)Authentication Success 71 Dr. Zhanqi XU, National Key Lab on ISN, Xidian University 2018/9/22