introduction to internet
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Introduction to Internet
WWW UserSchool of Computer Science
2007-2008
Aims
• Knowing Internet fundamentals
• Selecting the most important milestones
• Identifying the most important people and their contributions
• Enumerating the most usual protocols
• Identifying the basic services
What is Internet?
• Computer network (network of networks)
• Machines and networks using different technologies
• TCP/IP as communication protocol
Some figures
541,677,360
Jan 2008 (http://isc.org/ops/ds)
Internet evolution (1991)
Internet evolution (1991-1997)
Internet evolution (1997)
Initial goals (“officials”)
• To avoid any center. Each one manages its own networks
• Keep the network simple. Complex tasks done in nodes
• Implemented in any media and topology
To know more...
Andreu Veà i Baró: Historia, Sociedad Tecnología y Crecimiento de la Red. Una aproximación divulgativa a la realidad más desconocida de Internet.- PhD. Thesis
Available athttp://www.tdx.cecsa.es/TDX-1104104-101718
Some important people
• Leonard Kleinrock:
• Ray Tomlinson:
• Doug Englebart:
• Vinton Cerf:
• Tim Berners-Lee
• Marc Andreesen:
what did they?
Management Org.
• ISOC (www.isoc.org)Internet Society: standarisation and promotion
• IETF (www.ietf.org)The Internet Engineering Task Force: Internet evolution
• IAB (www.iab.org)Internet Architecture Board
• INTERNIC (www.internic.net)Domain registration
A network of networks
local host
remote host
gateway
152.6.98.211
TCP/IP
Hosts
• Any computer connected to Internet
• Capable of executing user final tasks
• 2 points of view
• locale: executes user programs
• remote: provides services
IP Addresses
• IP protocol needs an unique number for each machine (IP address)
• 4 numbers between 0 and 255158.42.9.125 (IPv4) … IPv6?
• Data is divided into small packages
• Each package is identified by the receiver IP
Types
A Class
B Class
C Class
D Class
0 Net (7 bits) Local (24 bits)
10 Net (14 bits) Local (16 bits)
110
1110 Broadcast address (28 bits)
Net (21 bits) Net (8 bits)
0
0
0
0
1 8 9 31
1 2 15 16 31
2 3 0 0 31
0 0 31
IP Ranges
Class Code Net Local From To Networks / hosts
A 0 7 24 0.1.0.0 126.0.0.0 126 / 16,000,000
B 10 14 16 128.0.0.0 191.255.0.0 16,000 / 65,000
C 110 21 8 192.0.0.0 223.255.255.0 2,000,000 / 254
D 1110 224.0.0.0 239.255.255.255 General diffusion
IPv6
• It uses 128 bits →2128 = 3.4 x 1038
• that means 0.6 x 1025 address / cm2
• there’re 1051 atoms in the Earth
• 8 groups of 4 hexadecimal digits
2001:0db8:85a3:08d3:1319:8a2e:0370:7334
Domain Name Server (DNS)
• use mnemonics ‘machine.domain’
• IP and name registered together
• security: avoid duplicates
• confort: routing tables
• Name Server: program that translates addresses from textual to numeric
TCP/IP ProtocolTransfer Control Protocol (TCP): Guarantees comm. without errors
Internet Protocol (IP): Isolates users from network media an topologies
Emissor • Divides data into packages and numbers them
Receiver • Orders received packages and composes the original message.
• If some package is missed, ask for it to be resended
Application Layer
Transport Layer
Internet Layer
Physical Layer
TCP/IP family
DNS
SMTP
TELNET
RPC
FTP
HTTP
TCP UDP
IP ICMP