What is the Internet?

1
What is the Internet?

• The US military wanted a network that was robust
  under enemy attack.
• US academics wanted a network that would allow
  researchers to share information and computing
  resources.
• Their joint efforts resulted in ARPAnet.
• ARPAnet was launched in 1969
• Internet is A global interconnected network of
  computer networks plus the information held in
  those networks.

2
Rules and conventionsAddresses

• Every computer that is directly connected to the
  Internet has two addresses.
• The formal address is the four number IP
  address (e.g. 139.80.91.23).
• The informal (human) address is the hostname
  (e.g. atlas.otago.ac.nz).
• A Domain Name Server (DNS) translates between the
  two.
• The human address may have an alias (e.g.
  cs.otago.ac.nz for atlas.otago.ac.nz).

3
Rules and conventionsDomain Names

• What means atlas.otago.ac.nz?
• Part after leftmost . is called domain name.
• Highest level (rightmost) is the country code or
  country domain (.nz New Zealand).
• Next level is more properly called the domain
  (of interest) (.ac academic).
• Below, the institution or subdomain (.otago).
• Finally the machine or local identifier (atlas).
• In the USA the highest level is the domain
  .com, .edu, .gov, ... Country code not used.

4
Rules and conventionsInternet Protocols TCP/IP

• TCP Transmission Control Protocol
   Controls correct transmission of a
  message chopped up in packets
• IP Internet Protocol
• Controls the routing from source to destination
  node. Use the IP addressing system of the Internet

5
Internet Services

• Electronic mail and mailing lists
• Newsgroups
• Telnet (remote login) and ftp (file transfer)
• Real-time communication
• World Wide Web