How The Internet Works

What Is The Internet?Decentralised global network of computers

Created by the US Defence Department’s Advanced Research Projects Agency in the 1960s

Lots of serviceshttp, ftp, smtp, ssh

Common protocol: TCP/IP

Loading A WebsiteGive me www.rawnet.com please

Sure - here you go

What Does It REALLY Ask For?Open a socket to the server

Send a request for a URL, optional headers

GET / HTTP/1.1Host: www.rawnet.comConnection: keep-aliveAccept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/48.0.2564.97 Safari/537.36Accept-Encoding: gzip, deflate, sdchAccept-Language: en-GB,en-US;q=0.8,en;q=0.6

How Does It Get There?DNS

IP addressing

Routing

DNS - Domain Name SystemInternet addressing uses numerical addresses

People use words

DNS maps words to numerical addresses hierarchy

Recursive lookup

Lots of caching

DNS Recursion

IP AddressesIPv4 - four parts 0-255

e.g. www.rawnet.com is 23.235.43.249

232 (4,294,967,296) addressesalready run out

NAT allows sharing and address re-use192.168.0.1

192.168.0.2

192.168.0.3

109.176.68.202

Private

192.168.0.1

192.168.0.2

192.168.0.3

Private

114.181.67.85

IP AddressesIPv6 - formalised 1998

128 bit address: 2128 addresses340,282,366,920,938,463,463,374,607,431,768,211,456

enough for an address for every atom on the surface of the Earth, and still have enough addresses left to do another 100+ Earths

Routing

Routing

A Word About CDNs

Learn more about Rawnet