Week7-Application Layer

Week7-Application Layer

现在有两个基本问题需要应用层解决 其一是 那个应用将获得数据 ,这个问题通过一个叫做端口的机制解决

• What does the Application Layer expect from the Transport Layer?

1. A reliable pipe that delivers data from another application across the Internet

• If you were “hacking” the Hypertext Transport Protocol using the ‘telnet’ command, what command would you send to the web server once you are connected to retrieve a document?

1. GET

• Which of the following are examples of applications in the application layer?
  Internet Explorer
  Chrome web browser
  Firefox
  Instant Messaging Client
  Microsoft Outlook
  Apple Mail
• When is the Internet 100% up and working?

1. It never is. It is constantly having pieces connect, fail, disconnect, reboot, etc.

• Last time! What are the layers of the internet, and the order in which we structure them?
  Application
  Transport
  IP
  Link
• What does the browser do when you click a Hypertext Link from your current web page to another web page?

1. It does a Request-Response Cycle

• **What does port 23 do? **

1. Telnet (Login)

• What does port 80 do?

1. HTTP

• RFCs are:
  Requests For Comment
  Issued by the Internet Engineering Task Force (IETF)
  The standards defining protocols on the Internet
• Which of the following is most like a TCP/IP port number:

1. Telephone extension

• What is a protocol?

1. A set of rules that govern how different components of the Internet interact with each other