基础计算机网络——应用层(Application Layer)笔记

【CS架构与P2P架构】

CS:

1.      Always-on server;

2.      Permanent IP address;

3.      Server farms for scaling;

P2P:

1.      No always-on server;

2.      Arbitrary end system;

3.      Hard to manage;

4.      Easy to expand;

5.      Communicate directly;

6.      Peers are intermittentlyconnected and change IP addresses;

 

【Post传参方法与URL(Get)传参方法】

Post:

  Input is uploaded to server in entity body;

URL:

  Input is uploaded in the URL filed of request line

 

【Cookie与Web Cache】

Cookie components:

1.      Cookie header lines in responseand request message;

2.      Cookie file is kept on user’shost; ( 存储在client上与3对应的文件)

3.      Back-end database at the website; (存储在server上与2对应的文件)

Web cache:

1.      Goal: satisfy client requestwithout involving original server;

2.      Approach: use proxy server;

3.      Effect: reduce response timeand reduce traffic;

 

【FTP文件传输协议】

Two connections: control connection anddata connection

 

【DNS域名服务器】

1.      Domain Name Server: translatehostname to IP address

2.      Protocol: UDP

3.      Functionality: host aliasing,mail server aliasing and load distribution;

 

【Electronic Mail电子邮件】

1.      3 components: user agents, mailservers, SMTP(between mail servers to send mail message)

2.      Sequence:

Message from A->user agentA->mail server A->mail server B->user agent B->message to B

3.      Mail access protocols: Pop,IMAP, HTTP, which are used to fetch mails from server to user agent.

 

【Decentralized Design去中心化设计】

   Advantages:

1.      Avoid single point of failure;

2.      Reduce traffic volume;