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;