comp101 Lecture ‘Internet’ abstract 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.

comp101 Lecture ‘Internet’ abstract 2

Rules and conventions:Addresses

• 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).

comp101 Lecture ‘Internet’ abstract 3

Rules and conventions:Domain 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.

comp101 Lecture ‘Internet’ abstract 4

Rules and conventions:Internet 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

comp101 Lecture ‘Internet’ abstract 5

Internet Services

• Electronic mail and mailing lists

• Newsgroups

• Telnet (remote login) and ftp (file transfer)

• Real-time communication

• World Wide Web