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



Star topology



Ring topology



Bus topology



Ethernet sharing



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


LANs are incompatible

Various LAN technologies are completely incompatible.

Accounting Dept.

Shipping Dept.


LANs are incompatible

Various LAN technologies are completely incompatible.

Accounting Dept.

Shipping Dept.

Simply connecting the cables cannot make them

work together


Wide Area Technologies ExistA 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


Wide Area Technologies Exist


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.


The Desirability of A Single Network …


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.



Diagrams of two nodes on the ARPANETIMP - Interface Message Processors


Internet Software

Computer software forms an important part of the technology that makes it possible to interconnect networks


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


An Open System

The Internet project aspired to produce an open system that permitted computers from all vendors to communicate.


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 #computers Year #computers1983 562 1991 500,0001984 1,024 1992 727,0001985 1,961 1993 1,200,0001986 2,308 1994 2,217,0001987 5,089 1995 4,852,0001988 28,174 1996 9,472,0001989 80,0001990 290,000


By 1999; a computer was added to the

Internet every second.


By 2006; more than 10 computers were added to the

Internet every second.


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



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



The NSFNET Backbone



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


In the UK … JANET

The Global Internet


In Europe … Ebone

The Global Internet


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


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


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


Communication Path

Sharing saves cost


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


A

B

C

D

A|CB|DA|CB|C

1st packet from A to C

1st packet from B to D

2nd packet from A to C

1st packet from B to C


A

B

C

D

A|CB|DA|CB|C





Packet Switching

Packet Switching Avoids Delay

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





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

10.0.0.1

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

10.0.0.1

Packets are Not All the Same Size

A

B

C

D

A|CB|DB|C

Packets can have different sizes

10.0.0.1

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


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


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


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

InterconnectingComputer

Use A Computer to Interconnect Networks


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


Interconnection Computers Pass Packets


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

The Hierarchical Structure of the Internet

Major ISP

Regional ISP

Local ISP

Local ISP

Major ISP

Regional ISP

Regional ISP

Local ISP

subscribers subscriberssubscribers

Where Packets Travel

Major ISP

Regional ISP

Local ISP

Local ISP

Major ISP

Regional ISP

Regional ISP

Local ISP

Interconnecting Networks was Revolutionary

InterconnectingComputer (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

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’sComputer AttachedTo the Internet

ISP’s Permanent Connection toThe 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 …

A Brief History of the Internet

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