Computer Networking A Top-Down Approach 笔记(一)

本文介绍了网络架构的基础概念,包括端系统、路由器、链路层交换机等组件的作用及工作原理。详细阐述了数据包在网络中的传输过程,并讨论了两种主要的宽带住宅接入方式:数字用户线路(DSL)和有线电视网络。此外,还分析了互联网服务提供商(ISP)的角色及其互联结构。

摘要生成于 C知道 ,由 DeepSeek-R1 满血版支持, 前往体验 >

Devices——hosts or end systems

 

End systems are connected together by a network of communication links and packet switches.

 

When one end system has data to send to another end system, the sending end system segments the data and adds header bytes to each segment. The resulting packages of information, known as packets, are then sent through the network to the destination end system, where they are reassembled into the original data.

 

Two most prominent types of packet switches——routers and link-layer switches. Both types of switches forward packets toward their ultimate destinations. Link-layer switches are typically used in access networks, while routers are typically used in the network core.

 

The sequence of communication links and packet switches traversed by a packet from the sending end system to the receiving end system is known as a route or path through the network. The

 

Packet-switched networks (which transport packets) are similar to transportation networks. Packet takes a path through a computer network.

 

End systems access the Internet through Internet Service Providers(ISP).

 

Each ISP is in itself a network of packet switches and communication links. ISPs also provide Internet access to content providers, connecting Web sites directly to the Internet.

 

ISPs that provide access to end systems must also be interconnected. These lower-tier ISPs are interconnected through national and international upper-tier ISPs. An upper-tier ISP consists of high-speed routers interconnected with high-speed fiber-optic links.

 

Protocols control the sending and receiving of information within the Internet.

 

The IP protocol specifies the format of the packets that are sent and received among routers and end systems.

 

peer-to-peer (P2P)

 

The applications are said to be distributed applications, since they involve multiple end systems that exchange data with each other.

 

The networking takes two (or more) communicating entities running the same protocol in order to accomplish a task.

 

All activity in the Internet that involves two or more communicating remote entities is governed by a protocol.

 

A protocol defines the format and the order of messages exchanged between two or more communicating entities, as well as the actions taken on the transmission and/or receipt of a message or other event.

 

End systems are also referred to as hosts. Hosts are sometimes further divided into two categories: clients and servers.

 

The two most prevalent types of broadband residential access are digital subscriber line (DSL) and cable.

 

A residence typically obtains DSL Internet access from the same local telephone company (telco) that provides its wired local phone access. Thus, when DSL is used, a customer's telco is also its ISP. As each customer's DSL modem uses the existing telephone line (twisted pair copper wire) to exchange data with a digital subscriber line access multiplexer (DSLAM,数字用户线接入复用器) located in the telco's local central office (CO). The home's DSL modem takes digital data and translates it to high frequency tones for transmission over telephone wires to the CO; the analog signals from many such houses are translated back into digital format at the DSLAM.

 

On the customer side, a splitter separates the data and telephone signals arriving to the home and forwards the data signal to the DSL modem. On the telco side, in the CO, the DSLAM separates the data and phone signals and sends the data into the Internet

 

Fiber optics connect the cable head end to neighborhood-level junctions, from which traditional coaxial cable is then used to reach individual houses and apartments. Each neighborhood junction typically supports 500 to 5,000 homes. Because both fiber and coaxial cable are employed in this system, it is often referred to as hybrid fiber coax (HFC).

 

Cable Internet access requires special modems, called cable modems. As with a DSL modem, the cable modem is typically an external device and connects to the home PC through an Ethernet port.

 

At the cable head end, the cable modem termination system (CMTS) turns the analog signal sent from the cable modems in many downstream homes back into digital format.

 

Cable modems divide the HFC network into two channels, a downstream and an upstream channel.

 

As with DSL, access is typically asymmetric, with the downstream channel typically allocated a higher transmission rate than the upstream channel.

 

Cable Internet access is that it is a shared broadcast medium(介质). In particular, every packet sent by the head end travels downstream on every link to every home and every packet sent by a home travels on the upstream channel to the head end.

 

FTTH concept— provide an optical fiber path from the CO directly to the home.

 

It is not until the fiber gets relatively close to the homes that it is split into individual customer-specific fibers. There are two competing optical-distribution network architectures that perform this splitting: active optical networks (AONs) and passive optical networks (PONs). AON is essentially switched Ethernet.

 

Each home has an optical network terminator (ONT), which is connected by dedicated optical fiber to a neighborhood splitter. The splitter combines a number of homes (typically less than 100) onto a single, shared optical fiber, which connects to an optical line terminator (OLT) in the telco's CO. The OLT, providing conversion between optical and electrical signals, connects to the Internet via a telco router. In the home, users connect a home router to the ONT and access the Internet via this home router. In the PON architecture, all packets sent from OLT to the splitter are replicated at the splitter.

转载于:https://www.cnblogs.com/Hu-Yan/p/8626078.html

出版者的话 作译者简介 译者序 前言 第1章 计算机网络和因特网 1.1/什么是因特网/1 1.1.1/具体构成描述/1 1.1.2/服务描述/4 1.1.3/什么是协议/5 1.2/网络边缘/6 1.2.1/客户机和服务器程序/7 1.2.2/接入网/8 1.2.3/物理媒体/13 1.3/网络核心/15 1.3.1/电路交换和分组交换/15 1.3.2/分组是怎样通过分组交换网形成其通路的/20 1.3.3/ISP和因特网主干/21 1.4/分组交换网中的时延、丢包和吞吐量/22 1.4.1/分组交换网中的时延概述/23 1.4.2/排队时延和丢包/25 1.4.3/端到端时延/26 1.4.4/计算机网络中的吞吐量/28 1.5/协议层次和它们的服务模型/30 1.5.1/分层的体系结构/30 1.5.2/报文、报文段、数据报和帧/33 1.6/攻击威胁下的网络/35 1.7/计算机网络和因特网的历史/38 1.7.1/分组交换的发展:1961~1972/38 1.7.2/专用网络和网络互联:1972~1980/39 1.7.3/网络的激增:1980~1990/40 1.7.4/因特网爆炸:20世纪90年代/41 1.7.5/最新发展/42 1.8/小结/42 本书路线图/43 课后习题和问题/44 复习题/44 习题/45 讨论题/49 Ethereal实验/49 人物专访/50 第2章 应用层 2.1/应用层协议原理/52 2.1.1/网络应用程序体系结构/53 2.1.2/进程通信/55 2.1.3/可供应用程序使用的运输服务/56 2.1.4/因特网提供的运输服务/57 2.1.5/应用层协议/60 2.1.6/本书涉及的网络应用/61 2.2/Web应用和HTTP协议/61 2.2.1/HTTP概况/62 2.2.2/非持久连接和持久连接/63 2.2.3/HTTP报文格式/65 2.2.4/用户与服务器的交互:cookie/68 2.2.5/Web缓存/70 2.2.6/条件GET方法/72 2.3/文件传输协议:FTP/73 2.4/因特网中的电子邮件/74 2.4.1/SMTP/76 2.4.2/与HTTP的对比/78 2.4.3/邮件报文格式和MIME/79 2.4.4/邮件访问协议/81 2.5/DNS:因特网的目录服务/84 2.5.1/DNS提供的服务/85 2.5.2/DNS工作机理概述/86 2.5.3/DNS记录和报文/90 2.6/P2P应用/94 2.6.1/P2P文件分发/94 2.6.2/在P2P区域中搜索信息/98 2.6.3/案例学习:Skype的P2P因特网电话/102 2.7/TCP套接字编程/103 2.7.1/TCP套接字编程/104 2.7.2/个Java客户机/服务器应用程序例子/105 2.8/UDP套接字编程/109 2.9/小结/114 课后习题和问题/115 复习题/115 习题/116 讨论题/120 套接字编程作业/121 Ethereal实验/122 人物专访/122 第3章 运输层 3.1/概述和运输层服务/124 3.1.1/运输层和网络层的关系/125 3.1.2/因特网运输层概述/126 3.2/多路复用与多路分解/127 3.3/无连接运输:UDP/133 3.3.1/UDP报文段结构/135 3.3.2/UDP检验和/135 3.4/可靠数据传输的原理/136 3.4.1/构造可靠数据传输协议/137 3.4.2/流水线可靠数据传输协议/144 3.4.3/回退N步/147 3.4.4/选择重传/149 3.5/面向连接的运输:TCP/154 3.5.1/TCP连接/154 3.5.2/TCP报文段结构/156 3.5.3/往返时延的估计与超时/160 3.5.4/可靠数据传输/162 3.5.5/流量控制/166 3.5.6/TCP连接管理/168 3.6/拥塞控制原理/173 3.6.1/拥塞原因与开销/173 3.6.2/拥塞控制方法/177 3.6.3/网络辅助的拥塞控制例子:ATMABR拥塞控制/178 3.7/TCP拥塞控制/180 3.8/小结/187 课后习题和问题/189 复习题/189 习题/190 讨论题/195 编程作业/196 Ethereal实验:探究TCP/196 Ethereal实验:探究UDP/196 人物专访/196 第4章 网络层 4.1/概述/199 4.1.1/转发和选路/200 4.1.2/网络服务模型/202 4.2/虚电路和数据报网络/203 4.2.1/虚电路网络/204 4.2.2/数据报网络/206 4.2.3/虚电路和数据报网络的由来/208 4.3/路由器工作原理/208 4.3.1/输入端口/210 4.3.2/交换结构/211 4.3.3/输出端口/212 4.3.4/何时出现排队/213 4.4/网际协议:因特网中的转发和编址/215 4.4.1/数据报格式/216 4.4.2/IPv4编址/220 4.4.3/ICMP:互联网控制报文协议/230 4.4.4/IPv6/232 4.4.5/IP安全性概述/236 4.5/选路算法/237 4.5.1/链路状态选路算法/239 4.5.2/距离向量选路算法/242 4.5.3/层次选路/248 4.6/因特网中的选路/250 4.6.1/因特网中自治系统内部选路:RIP/251 4.6.2/因特网中AS内部选路:OSPF/253 4.6.3/自治系统间的选路:BGP/255 4.7/广播和多播选路/260 4.7.1/广播选路算法/260 4.7.2/多播/264 4.8/小结/269 课后习题和问题/270 复习题/270 习题/271 讨论题/277 编程作业/278 Ethereal实验/278 人物专访/279 第5章 链路层和局域网 5.1/链路层:概述和服务/281 5.1.1/链路层提供的服务/281 5.1.2/链路层在何处实现/283 5.2/差错检测和纠错技术/284 5.2.1/奇偶校验/285 5.2.2/检验和方法/287 5.2.3/循环冗余检测/287 5.3/多路访问协议/288 5.3.1/信道划分协议/290 5.3.2/随机接入协议/292 5.3.3/轮流协议/297 5.3.4/局域网/297 5.4/链路层编址/298 5.4.1/MAC地址/298 5.4.2/地址解析协议/300 5.5/以太网/303 5.5.1/以太网帧结构/304 5.5.2/CSMA/CD:以太网的多路访问协议/307 5.5.3/以太网技术/309 5.6/链路层交换机/310 5.6.1/交换机转发和过滤/311 5.6.2/自学习/312 5.6.3/链路层交换机的性质/313 5.6.4/交换机和路由器的比较/314 5.7/PPP:点对点协议/315 5.8/链路虚拟化:网络作为链路层/318 5.8.1/异步传输方式/318 5.8.2/多协议标签交换/322 5.9/小结/324 课后习题和问题/325 复习题/325 习题/325 讨论题/329 Ethereal实验/329 人物专访/329 第6章 无线网络和移动网络 6.1/概述/332 6.2/无线链路和网络特征/334 6.3/WiFi:802.11无线LAN/339 6.3.1/802.11体系结构/339 6.3.2/802.11MAC协议/342 6.3.3/IEEE802.11帧/345 6.3.4/在相同的IP子网中的移动性/348 6.3.5/802.11中的高级特色/348 6.3.6/802.11以外的标准:蓝牙和WiMAX/349 6.4/蜂窝因特网接入/352 6.4.1/蜂窝网体系结构概述/353 6.4.2/蜂窝网标准和技术:简要回顾/354 6.5/移动管理:原理/356 6.5.1/寻址/358 6.5.2/选路到移动节点/359 6.6/移动IP/363 6.7/蜂窝网中的移动性管理/366 6.7.1/对移动用户呼叫的选路/367 6.7.2/GSM中的切换/368 6.8/无线和移动性:对高层协议的影响/370 6.9/小结/372 课后习题和问题/372 复习题/372 习题/373 讨论题/375 Ethereal实验/375 人物专访/376 第7章 多媒体网络 7.1/多媒体网络应用/378 7.1.1/多媒体应用的例子/378 7.1.2/当今因特网上的多媒体障碍/380 7.1.3/因特网应该如何演化才能更好地支持多媒体/381 7.1.4/音频和视频压缩/382 7.2/流式存储音频和视频/384 7.2.1/通过Web服务器访问音频和视频/385 7.2.2/从流式服务器向助手应用程序发送多媒体/386 7.2.3/实时流协议/388 7.3/充分利用尽力而为服务/390 7.3.1/尽力而为服务的限制/390 7.3.2/在接收方消除音频的时延抖动/392 7.3.3/从丢包中恢复/394 7.3.4/在今天的因特网中分发多媒体:内容分发网络/397 7.3.5/规划尽力而为网络以提供服务质量/399 7.4/实时交互应用的协议/400 7.4.1/RTP/400 7.4.2/RTP控制协议/403 7.4.3/SIP/405 7.4.4//H.323/409 7.5/提供多个等级的服务/410 7.5.1/启发研究的场景/411 7.5.2/调度和监管机制/414 7.5.3/区分服务/419 7.6/提供服务质量保证/423 7.6.1/个有启发的例子/423 7.6.2/资源预约、呼叫准入、呼叫建立/424 7.6.3/在因特网中确保QoS:Intserv和RSVP/425 7.7/小结/427 课后习题和问题/428 复习题/428 习题/429 讨论题/433 编程作业/433 人物专访/434 第8章 计算机网络中的安全 8.1/什么是网络安全/436 8.2/密码学的原则/438 8.2.1/对称密钥密码学/440 8.2.2/公开密钥加密/443 8.3/报文完整性/447 8.3.1/密码散列函数/447 8.3.2/报文鉴别码/449 8.3.3/数字签名/450 8.4/鉴别/455 8.4.1/鉴别协议ap1.0/455 8.4.2/鉴别协议ap2.0/456 8.4.3/鉴别协议ap3.0/456 8.4.4/鉴别协议ap3.1/457 8.4.5/鉴别协议ap4.0/457 8.4.6/鉴别协议ap5.0/458 8.5/电子邮件安全/460 8.5.1/安全的电子邮件/461 8.5.2/PGP/464 8.6/使TCP连接安全:SSL/465 8.6.1/宏观描述/466 8.6.2/更完整的描述/468 8.7/网络层安全性:IPsec/469 8.7.1/鉴别首部协议/469 8.7.2/ESP协议/470 8.7.3/SA和密钥管理/471 8.8/使无线LAN安全/471 8.8.1/有线等效保密/472 8.8.2/IEEE802.11i/473 8.9/运行安全性:防火墙和入侵检测系统/475 8.9.1/防火墙/475 8.9.2/入侵检测系统/479 8.10/小结/482 课后习题和问题/482 复习题/482 习题/483 讨论题/485 Ethereal实验/485 人物专访/485 第9章 网络管理 9.1/什么是网络管理/487 9.2/网络管理的基础设施/490 9.3/因特网标准管理框架/493 9.3.1/管理信息结构:SMI/494 9.3.2/管理信息库:MIB/496 9.3.3/SNMP协议运行和传输映射/498 9.3.4/安全性和管理/500 9.4/ASN.1/502 9.5/小结/506 课后习题和问题/506 复习题/506 习题/507 讨论题/507 人物专访/507 参考文献/509
评论
添加红包

请填写红包祝福语或标题

红包个数最小为10个

红包金额最低5元

当前余额3.43前往充值 >
需支付:10.00
成就一亿技术人!
领取后你会自动成为博主和红包主的粉丝 规则
hope_wisdom
发出的红包
实付
使用余额支付
点击重新获取
扫码支付
钱包余额 0

抵扣说明:

1.余额是钱包充值的虚拟货币,按照1:1的比例进行支付金额的抵扣。
2.余额无法直接购买下载,可以购买VIP、付费专栏及课程。

余额充值