The Internet

Definition: Network of networks. Began in 1969, DOD project called ARPANET. Early 1980’s NSF creates NSFnet NSF takes over both by mid ’80’s The Internet is created.

IP Addresses Needed a way to identify individual computers on the internet. Hit upon the idea of IP addresses. Give each computer a unique number (address) and then you can send information to it. Stands for:  Internet Protocol Addresses

IP Addresses Format:  x.x.x.x  Where each x is a number from 0 to 255. Do the math:  256*256*256*256 = 4,294,967,296 Despite this, we are running out of IP addresses IPv6 may take care of this

TCP/IP Early on, realized they needed a better way to transfer files. Large files moved slowly, clogged up the network, and if damaged in transit, were a pain to re-send. So let’s break up the large files into smaller ones, and send the smaller pieces. That’s TCP/IP

TCP/IP Transmission Control Protocol/Internet Protocol Protocol for how to:  break up information into standard sized “packets”  address each one,  send them out to their destination,  reassemble them upon receipt.

Domain Name System Remember each computer has a unique IP address. To connect to that computer, use its IP address. To connect to the alphas: To connect to miller: ???.??? Way too tedious.

Domain Name System Early on, realized the need to associate unique names with each IP address. Domain Name System established:  A single organization responsible for assigning domain names. IANA  A decentralized system of distributing the names domain name servers

Domain Names Names separated by dots  E.g., Last part is called top-level domain (TLD) or zone.  Usually 3 or 2 letters long. Next part is second-level domain.  The unique name of the organization to whom the name belongs. From there, individual organization can name the individual computer whatever they want.

In summary IP addresses give each computer a unique address. TCP/IP is the protocol that made sending files over the internet possible. Domain names make it easier to remember computer names. Domain name servers handle the translation from names into IP addresses.

The WWW

World Wide Web The World Wide Web  Tim Berners-Lee working at CERN decided he wanted a way to share information easily with his colleagues.  worlDwidEweb ca 1991

HTTP: HyperTextTtransfer Protocol URL: Uniform Resource Locator HTML: HyperText Markup Language Web Servers Four inventions

HTTP Hypertext Transfer Protocol

URLs Format: [scheme]://[host name] / [path name]  Scheme — the type of transfer/connection you have Usually http  Host name — the name of the computer to which you are connecting.  Path name — the full path name to the file you are looking for. Series of directories ending in a file name. If a file is not specified, by default browser looks for an index.html file.

HTML HyperText Markup Language Plain text document with hidden “codes” that tell a browser how to format the information. Based on structured documents in which the content of the document is separated from the formatting of the document.  This is a heading And this is some formatted text This is a list Item 1 Item2

Web Servers The Internet

1991 – 1994 tremendous growth 1993: NCSA Mosaic  Written by Marc Andreesen.  Incorporated images into text.  Ran under Unix.  By end of year, PC and Mac versions were out. Graphical Web Browser

Internet & Web Growth As of January 2003  171,638,297 hosts  Taken from: