传输层的功能 传输层协议要素 Internet的传输层： 用户数据报协议（UDP） 传输控制协议（TCP） Berkeley Sockets

IP datagram format IP protocol version 32 bits Imber total datagram header lenath lver/head pe length(bytes) (bytes) Hlen service

TCP segment structure 32 bits URG: urgent data (generally not used) source port #f dest port counting by bytes sequence number

Chapter 7: Network security Foundations: what is security? crypfography authentication message integrity key distribution and certification Security in practice: application layer: secure e-mail

《网络工程师考试同步辅导》教学资源（参考资料）第2章 数据通信基础

• 数据通信系统 • 基本概念 • 传输介质 • 数据编码 • 多路复用技术 • 数据交换技术 • 差错控制 • 数据通信性能指标

Network layer functions transport packet from sending to receiving hosts network layer protocols in physical every host, router data link physical data link

1建设目标 2需求分析 3校园网系统集成方案的规划设计 4校园网应用系统的集成实现 5校园网系统集成的特点分析

Summary of mac protocols What do you do with a shared media? Channel Partitioning by time, frequency or code Time Division, Code Division, Frequency Division Random partitioning dynamic

Link Layer: setting the context actual PDu flow Router r1 applicatio pp lication transport trar sport network net vork data link