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Internet skills in 30 min

What is IP address and MAC address?

  • IP address is an address of the computer in the internet. MAC address is an "ID number" of the "network interface card (NIC)" of the computer.
  • Your computer's MAC address does not change forever (unless you replace its NIC).
  • Your computer's IP address can change if you change it's connection to the internet.
  • It is like your name never changes but your residence address changes when you move from one city to another city.

Exercise

  • Find IP address and MAC address of the computer in front of you.
  • Find IP address and MAC address of your smartphone.

https://www.cman.jp/network/support/go_access.cgi

"Global IP address" and "private IP address"

  • "Global IP address" can be accessed from all over the world DIRECTLY!
  • "Private IP address" can be accessed from inside a small network.

Exercise

  • Is the IP address of the computer in front of you global or private?
  • Is the IP address of your smartphone global or private?

Discuss with your friend

  • What are the advantages and disadvantages of global and private IP address?

Hostname and DNS

Exercise

  • Find the IP address of www.tsukuba.ac.jp
  • Find a hostname of 130.158.200.27

What is a "server" and a "client"?

"Client" is a computer in front of you now. "Server" is a computer working for you through a network. Mostly it is at somewhere else.

Example:

  • You are watching this website on your client. But it's contents are provided by a server, which is our lab's computer named "pen" (or more officially, "pen.envr.tsukuba.ac.jp"). It is placed in a building near the university library.

Remote access by SSH

  • You can manipulate a server computer freely, using "SSH".

Exercise

  • Get user account from Nasahara and try SSH access to 130.158.200.25
$ ssh username@130.158.200.25
  • Try SSH access to pen.envr.tsukuba.ac.jp
$ ssh username@pen.envr.tsukuba.ac.jp
  • Try to see who is using the server:
$ w

What is "protocol"?

"Protocol" is a rule (procedure) of communication between computers.

Example:

  • You are watching this website. It's contents are transferred to your client from the "pen" server to your client using a protocol called "HTTP" (hypertext transfer protocol).

What is "port"?

Last modified:2020/03/14 17:37:24
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References:[Watershed management 2018]