北京邮电大学《计算机网络》Computer_Network_Ch5B_Network Layer.pdf

COMPUTER NETWORK 计算机网络 北京邮电大学 计算机学院 王晓茹 CHAPTER 5 THE NETWORK LAYER CONTENTS PART 2 ： Internet上的网络层 5.1 网络层的设计要点 * 5.2 路由算法 * 5.3 拥塞控制 * 5.4 服务质量 * 5.5 网络互联 *5.6 网络层IP协议 IP地址 IP数据报结构 IP控制协议 IPv6和内部/外部路由协议 The Top 10 Principles (Clark) 1.Make sure it works • Do not finalize the design or standard until multiple prototypes have successfully communicated with each other 2.Keep it simple (KISS: Keep It Simple, Stupid!) • If a feature is not absolutely essential, leave it out, especially if the same effect can be achieved by combining other features 3.Make clear choices • If there are several ways of doing the same thing, choose one 4.Exploit modularity 5.Expect heterogeneity 6.Avoid static options and parameters • If parameters are unavoidable (e.g., maximum packet size), it is best to have the sender and receiver negotiate a value than defining fixed choices 7.Look for a good design; it need not be perfect 8.Be strict when sending and tolerant when receiving 9.Think about scalability 10.Consider performance and cost The Internets Network Layer Vinton Cerf, Robert Kahn 1974, Turing Award 2004 • The Internet a Collection of Subnetworks (Autonomous Systems) that are interconnected • Its j ob is to provide a best-efforts way to transport datagrams from source to destination Internet上的网络层协议IP 网际协议 IP 是 TCP/IP 体系结构中两个最主要的协议之一 。 与 IP 协议配套使用的还有四个协议： • 地址解析协议 ARP (Address Resolution Protocol) • 逆地址解析协议 RARP (Reverse