A Brief History of the Internet

Internet: The early years … The Proliferation of LANs  Engineers have devised many LAN technologies  LAN performance determines cost; high performance LANs are more expensive  A particular LAN technology may only work with specific computers

Internet: The early years … The Proliferation of LANs Star topology

Internet: The early years … The Proliferation of LANs Ring topology

Internet: The early years … The Proliferation of LANs Bus topology

Internet: The early years … The Proliferation of LANs Ethernet sharing

Internet: The early years … The Proliferation of LANs  A LAN technology is chosen for its speed, ease of use, and the availability of interfaces for specific computers. Most large organization use many LAN technologies

Internet: The early years … LANs are incompatible  Various LAN technologies are completely incompatible. Accounting Dept. Shipping Dept.

Internet: The early years … LANs are incompatible  Various LAN technologies are completely incompatible. Accounting Dept. Shipping Dept. Simply connecting the cables cannot make them work together

Internet: The early years … Wide Area Technologies Exist A wide area network technology (WAN) differs from a set of disjoint transmission lines because the WAN includes an additional special purpose computer at each side that connects to the transmission lines and keeps communication independent of the computers that use the WAN

Internet: The early years … Wide Area Technologies Exist

Internet: The early years …  Few WANs, Many LANs  WANs and LANs are Incompatible  Many LAN and WAN technologies exist, and most are incompatible with each other. One cannot produce a usable, large network merely by interconnecting the wires from two different networks.

Internet: The early years …  The Desirability of A Single Network …

Internet: The early years …  The Internet Emerges …  ARPANET …  Advanced Research Project Agency (ARPA) funded research projects to research new approaches to connecting LANs and WANs.  A prototype system that researchers built became known as an internetwork – Internet.

Internet: The early years …  The Internet Emerges … Diagrams of two nodes on the ARPANET IMP - Interface Message Processors

Internet: The early years …  The Internet Emerges …

Internet: The early years …  The Internet Emerges …

Internet: The early years …  Internet Software  Computer software forms an important part of the technology that makes it possible to interconnect networks

Internet: The early years …  The Name is TCP/IP  Two pieces of Internet software stand out as particularly important and innovative  Internet Protocol – software provide basic communication  Transmission Control Protocol – Provide reliable communication

Internet: The early years …  An Open System  The Internet project aspired to produce an open system that permitted computers from all vendors to communicate.

Internet: The early years …  Summary …  The Internet began as a research project funded by ARPA. Researchers studied ways to connect computers that used various kinds of networks. The name Internet refers to both the project and the prototype network system that researchers built.  TCP/IP is the software necessary to make the Internet works. The software hides the detail of the underlying hardware and provides the illusion of a seamless system.  The Internet is an open system.

Internet: Incredible Growth  1981 – The Internet connects about 100 computers at research sites and universities  20 years later – 60,000,000 Year#computersYear#computers , , , , ,200, , ,217, , ,852, , ,472, , ,000

Internet: Incredible Growth

By 1999; a computer was added to the Internet every second.

Internet: Incredible Growth By 2006; more than 10 computers were added to the Internet every second.

Internet: Incredible Growth  Factors contribute to its growth …  Advances in computer science research – the introduction of UNIX operating system  UNIX meets TCP/IP – enables connection of LANs to the Internet  US Military Chose the Internet – The military funded and adopted the Internet, technologies were developed at civilian sites

Internet: Incredible Growth  Factors contribute to its growth …  National Science Foundation (NSF) Takes a Leading Role – connect universities to the Internet  NSF decided that to keep the US competitive, it needed to extend network access to every science and engineering researcher.  The NSFNET

Internet: Incredible Growth  Factors contribute to its growth …  The NSFNET Backbone

Internet: Incredible Growth  Factors contribute to its growth …  The ANS Backbone – IBM, MERIT, and MCI formed a nonprofit company, Advanced Networks and Services (ANS)  ANS owned the transmission lines and computers that comprised the network – ARPANET and NSFNET were funded by government  First step toward commercialization and privatization of the Internet

The Global Internet  Internet starts from the USA …expanded to the globe  Electronic mail connection – use existing voice telephone network – require a modem and a piece of communication software

The Global Internet  Internet starts from the USA …expanded to the globe  In the UK … JANET

The Global Internet  Internet starts from the USA …expanded to the globe  In Europe … Ebone

The Global Internet  Internet starts from the USA …expanded to the globe  In Hong Kong … HARNET

The Global Internet 1998, every populated country in the world is connected

Internet: A Global Information Infrastructure  Infrastructure – basic foundations on which society depends on – electricity power stations and supply facilities, railways, roads …  New infrastructure makes new industries possible

Internet: A Global Information Infrastructure  Communication Infrastructure  Postal mail services adopted the nation of universal access and delivery; and individual and send a letter to any other individual.  The telegraph changed the basic communication infrastructure because it introduced high speed delivery  Telephone changed the communication infrastructure by extending communication services to individual homes and offices, and by providing the instantaneous communication needed for interactive conversation

Internet: A Global Information Infrastructure  The Internet Infrastructure  The basic Internet communication facilities are both general and efficient, almost any network applications can use the Internet  The Internet offers a wide variety of services. Most of the services currently available had not been invented when the Internet was first designed.  The Internet is a global infrastructure. Although it offers many services, the Internet’s chief advantage lies in the design of TCP/IP software that has accommodated changes in computers, networks, and services

Summary  Many different LAN technologies that are completely incompatible.  WANs exist  Few WANs, Many LANs  WAN and LAN are incompatible  Desirable to have a single seamless network

Summary  ARPANET  ICP/IP  Open Systems  Computer science research, UNIX, NSFNET, TCP/IP … contributed to the rapid growth of the Internet.  Internet is a global information infrastructure.

Sharing transmission path Communication Path

Sharing transmission path Communication Path Sharing saves cost

Sharing transmission path Communication Path Sharing introduces delay

Sharing transmission path Communication Path Sharing introduces delay

Sharing using Selectable Channels Communication Path Carrier 1 Carrier 2

Sharing using Selectable Channels Communication Path Carrier 1 Carrier 2 Each channel is assigned a unique carrier which encodes the information of that communication channel

Sharing by Taking Turns A B C D Data to be transmitted Divide data to be transmitted into small trunks, call a packet; and transmit one packet at a time

Sharing by Taking Turns A B C D A|CB|DA|CB|C 1 st packet from A to C 1 st packet from B to D 2 nd packet from A to C 1 st packet from B to C

Sharing by Taking Turns A B C D A|CB|DA|CB|C 1 st packet from A to C 1 st packet from B to D 2 nd packet from A to C 1 st packet from B to C Packet Switching

Packet Switching Avoids Delay

A customer ordered a single item Another ordered 50 items

Each packet must be labeled A B C D A|CB|DA|CB|C 1 st packet from A to C 1 st packet from B to D 2 nd packet from A to C 1 st packet from B to C

Computers Have Addresses A B C D A|CB|DA|CB|C Each computer attached to the network is assigned a unique number called address

Computers Have Addresses A B C D A|CB|DA|CB|C Each packet contains the address of the computer that send it and the address of the computer to which it is sent

Packets are Not All the Same Size A B C D A|CB|DB|C Packets can have different sizes

Packets Transmission Seems Instantaneous A B C D A|CB|DB|C A packet switching system permits multiple computers to communicate across a shared network with minimal delay because it divides each conversation into small packets and arranges for the computer that sharing a network takes turns sending packets

Sharing is Automatic A B C D A|CB|DB|C From a computer’s point of view, obtaining fair access to a shared network is automatic – the network hardware handles the details.

Many Devices Can Use Packet Switching A B C D A|CB|DB|C Many type of devices can connect directly to a computer network, each such device must contain a small computer that handles communication

Relevance to the Internet All data is transferred across the Internet in packets

Relevance to the Internet A sender divides a message or document into packets and transfer the packets across the Internet

Relevance to the Internet A receiver re-assembles the original message from the packets that arrive.

Relevance to the Internet Packets from many machines traverse the Internet at the same time.

Summary  Packet switching – a fundamental technique used to ensure faire access to shared network resources.  Before data can be transferred across a network, it must be divided into small trunks – packets  Each computer connected to a network has a unique address  Each packet contains a header – records the sending and receiving computers’ addresses  Each computer takes turns to send its packet. One each turn, a computer sends one packet.

Internet: A Network of Networks How multiple packet switching networks can be interconnected to form an Internet that function like a single, large network.

Use A Computer to Interconnect Networks Interconnecting Computer

Use A Computer to Interconnect Networks Interconnecting Computer Computers that interconnect networks are dedicated to the interconnection task. They can use conventional hardware and run on special-purpose software that starts automatically when the system is powered on and remains operating all the time.

Interconnection Computers Pass Packets Interconnecting Computer

Interconnection Computers Pass Packets Interconnecting Computer

Interconnection Computers Pass Packets Interconnecting Computer

Interconnection Computers Pass Packets Interconnecting Computer

Interconnection Computers Pass Packets Interconnecting Computer An interconnect ing computer is call router

Routers are Building Blocks of the Internet  The Internet is not a single computer network  It consists of thousands of computer networks interconnected by dedicated, special purpose computers called routers

Routers are Building Blocks of the Internet  The Internet is not a single computer network  It consists of thousands of computer networks interconnected by dedicated, special purpose computers called routers

The Hierarchical Structure of the Internet Major ISP Regional ISP Local ISP Local ISP Major ISP Regional ISP Regional ISP Local ISP subscribers

Where Packets Travel Major ISP Regional ISP Local ISP Local ISP Major ISP Regional ISP Regional ISP Local ISP

Where Packets Travel Major ISP Regional ISP Local ISP Local ISP Major ISP Regional ISP Regional ISP Local ISP

Where Packets Travel Major ISP Regional ISP Local ISP Local ISP Major ISP Regional ISP Regional ISP Local ISP

Where Packets Travel Major ISP Regional ISP Local ISP Local ISP Major ISP Regional ISP Regional ISP Local ISP

Where Packets Travel Major ISP Regional ISP Local ISP Local ISP Major ISP Regional ISP Regional ISP Local ISP

Where Packets Travel Major ISP Regional ISP Local ISP Local ISP Major ISP Regional ISP Regional ISP Local ISP

Where Packets Travel Major ISP Regional ISP Local ISP Local ISP Major ISP Regional ISP Regional ISP Local ISP

Interconnecting Networks was Revolutionary Interconnecting Computer (Router)

Summary  To the user the Internet seems to be a single network  It in fact consists of thousands of networks interconnected by a dedicated device known as routers.  A router can connect LAN/LAN, LAN/WAN, WAN/WAN  Networks in the Internet are arranged into a conceptual hierarchy of ISPs.  Using routers to interconnect networks produced a revolution.

ISPs: Broadband and Wireless Access  How your compute can connect to and use the Internet

ISPs: Broadband and Wireless Access  How your compute can connect to and use the Internet

Internet Service Providers and Fees  A company that provides Internet access is known as an Internet Service Provider (IPS)  ISP levy two types of fees  A charge for using the Internet  A charge for a physical connection to the Internet

Leased Line  Dedicated connection, available all the time (24/7)  Expensive  Large business users

Dial-Up Access User’s Computer Modem Voice Telephone system Modem ISP’s Computer Attached To the Internet ISP’s Permanent Connection to The Internet

Modern Technologies Offer Inexpensive Dedicated Access  Cable Modem – From cable TV …  DSL (ADSL) – Digital subscriber line (Asynchronous digital subscriber line)  Wireless Access

Modern Technologies Offer Inexpensive Dedicated Access  DSL (ADSL) for residential users  A separate pair of copper wires connects each residence to the telephone office  The technology sends digital data over the same wires that are used for conversational telephone service, there is no interference. Telephone calls do not interfere with Internet use, and Internet use does not interfere with telephone calls.

Wi-Fi and 3G …  Most laptop has Wi-Fi …  3G …Mobile phone access to the Internet …