计算机网络综述：
第一章的学习与数据库概论不同，在理解方面存在太多偏差，缺乏通讯的知识，对于庞杂的概念犹如学习软需，但实际上更像是计组，对于计算机网络的相关实例不够熟悉，难以把握本课程的主线。同时，理论结合实际，习题是必要的。
知乎回答：计算机网络微课程
在阅读王道考研资料后，对于计算机网络有一定的了解，可以进行笔记整理
同时，可以观看计算机网络微课堂获取更多知识
Chapter 1. Introduction
以Internet为例,对于计算机网络大致了解，熟悉相关术语terminology
Terms :
- TCP: Transmission Control Protocol
- UDP: User Datagram Protocol
- ISP: Internet Service Provider
- LAN: Local Area Network
- WAN: Wide Area Network
- FDM: Frequency Division Multiplexing
- TDM: Time Division Multiplexing
1.1 What is the internet?
Computer Networks:
A computer network is composed of multiple computers connected together using a telecommunication system(电信系统) for the purpose of sharing data, resources and communication.
1.1.1 Composition of Computer Network
- Hardware
- End Systems: Host, PC, Mainframe(大型机), Client, Workstation, Server
- Intermediate Systems: Communications: Switch, Router [交换设备]
- Interface: Network interface card(NIC), Modem [通信处理机]
- Medium: Twisted pair, Coaxial cable, Fiber, Wireless [通信链路]
- Software
- Protocol（协议）: CSMA/CD, TCP/IP, UDP, PPP, ATM
- Applications: HTTP, SMTP, FTP, Telnet
1.1.2 Applications of Networks
- Resource Sharing
- Information Sharing
- Communication
- Ubiquitous Computing(普适计算)
- Mobile Users
1.1.3 Category of Computer Networks
- Classified by Topology
- Bus Topology
- Star & Tree Topology
- The star topology is the most commonly used architecture in Ethernet LANs.
- Ring Topology
- Classified by scale
- LAN
- WAN
- Internet
- Classified by boundary
- Intranet （Private Networks）
- Extranet （Public Networks）
1.1.4 What’s a protocol?
protocols define format,order of msgs sent and received among network entities, and actions taken on msg transmission, receipt
定义了两个或多个网络实体之间交换的报文格式和顺序，以及报文发送或接收一条报文或其他事件采取的动作。
1.2 Internet History
- 1961-1972: Early packet-switching principles
- 1972-1980: Internetworking, new and proprietary nets
- 1980-1990: new protocols, a proliferation of networks
- 1990, 2000’s: commercialization, the Web, new apps
- ……
1.3 Network edge
network structure：
- network edge：
- applications and hosts
- network core:
- routers
- network of networks
- access networks, physical media：
- communication links
……
1.4 The Network Core
- Mesh of interconnected routers
- the fundamental question: how is data transferred through net?
- circuit switching:
- dedicated circuit per call: telephone net
- packet-switching:
- data sent thru net in discrete “chunks”
- circuit switching: