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ChrisLi-Tech

Communication and internet technology

/ 3 min read

Table of Contents

Goals of chapter

By the end of this chapter you should be able to:

  • show understanding of circuit switching

  • Show understanding of packet switching

  • Show understanding of why a protocol is essential for communication between computers.

  • Show understanding of how protocol implementation can be viewed as stack, where each,layer has its own functionality.

  • Show understanding of the TCP/IP protocol suite

  • Show understanding of protocols(HTTP, FTP, POP3,IMAP. SMTP. BitTorrent) and their purpose.

Transmittion modes

For communication over an internetwork, there are two possible approaches:

  • Circular switching

  • Packet switching

Examples:

  • Make a phone call —Circuit switching

  • Send a email

  • Transfor a photo to your classmate

Circuit switching

#####Def

  • Dedicated circuit/channel is created between the sender and the receiver / 每个人使用专有通道

  • A connection is established before/at the start of the communication / ex: 打电话前拨号的过程

  • The connection lasts for the duration of the connection // circuit released at end of the communication / 在信息传输的过程中，专用线路将会被持续占用。直至两端断开连接。

  • All data transmitted along the same route / 一旦通道建立完成，通信过程中的所有数据都是通过此通道进行传输。

The features of circuit switching

  • A dedicated channel is created // not sharing channel

  • It can use all bandwidth

  • 2-way real time conversation is allowed

  • No delay as no switching

  • Data arrives in the order it is sent

  • The quality of service is guaranteed

Packet switching

  • A circuit does not have to be established at the start of the communication

  • The data to be sent is divided into packets/ 打包传输

  • The packets can travel along different routes from node to node/ 动态路径分配

  • Packets are reassembled in the correct order at the receiver’s end/ 接受数据包后排序

  • Must wait until the last packet is received to put the data back together/ 必须接收到所有数据包

Features of packet switching

  • Allows for error checking

  • Real time transmission is not required

  • Smaller amounts of data are sent (than voice calls) therefore dedicated line/ higher bandwidth is not required // can share the bandwidth

  • It make full use of the available capacity by using alternative routes

  • Doesn’t matter if data arrives out of order

随着技术进步和带宽增加，我们可以使用packet switching 实现一些circuit switching 的特性：

  • 网络电话 VoIP

  • 直播串流 Streaming