Internet Historyand Growth

KOS 1110 COMPUTER IN SCIENCE

What Was the“Victorian Internet”

The Telegraph - invented in the1840s

Signals sent over wires that wereestablished over vast distances

Used extensively by the U.S.Government during the AmericanCivil War, 1861 - 1865

Morse Code was dots and dashes,or short signals and long signals

The electronic signal standard of+/- 15 v. is still used in networkinterface cards today

Famous Quote FromSir Isaac Newton

“If I have been able to see farther thanothers, it was because I stood on theshoulders of giants.”

What Is the Internet?

A network of networks, joining many government,university and private computers together and providingan infrastructure for the use of E-mail, bulletin boards, filearchives, hypertext documents, databases and othercomputational resources

The vast collection of computer networks which form andact as a single huge network for transport of data andmessages across distances which can be anywhere fromthe same office to anywhere in the world

The largest network of networks in the world Uses TCP/IP protocols and packet switching Runs on any communications substrate

What is the Internet?

From Dr. Vinton Cerf,Co-Creator of TCP/IP

Brief History of the Internet

1968 - DARPA (Defense Advanced Research Projects Agency)contracts with BBN (Bolt, Beranek & Newman) to create ARPAnet

1970 - First five nodes: UCLA Stanford UC Santa Barbara U of Utah, and BBN

1974 - TCP specification by Vint Cerf 1984 – On January 1, the Internet with its 1000 hosts

converts en masse to using TCP/IP for its messaging

*** Internet History ***

A Brief Summary of theEvolution of the Internet

1945 1995

MemexConceived

1945

WWWCreated

1989

MosaicCreated

1993

AMathematical

Theory ofCommunication

1948

PacketSwitchingInvented

1964

SiliconChip1958

First VastComputerNetwork

Envisioned1962

ARPANET1969

TCP/IPCreated

1972

InternetNamed

andGoes

TCP/IP1984

HypertextInvented

1965

Age ofeCommerce

Begins1995

From Simple, But Significant Ideas Bigger Ones Grow1940s to 1969

1945 1969

We can accessinformation using

electronic computers

We do it reliably with “bits”,sending and receiving data

We can do it cheaply by usingDigital circuits etched in silicon.

We can accomplish a lot by having avast network of computers to use for

accessing information and exchanging ideas

We will prove that packet switchingworks over a WAN.

Packet switching can be used tosend digitized data though

computer networks

Hypertext can be used to allowrapid access to text data

From Simple, But Significant Ideas Bigger Ones Grow1970s to 1995

1970 1995

Ideas from1940s to 1969

We need a protocol for Efficientand Reliable transmission ofPackets over a WAN: TCP/IP

The ARPANET needs to convert toa standard protocol and be renamed to

The Internet

Computers connected via the Internet can be usedmore easily if hypertext links are enabled using HTML

and URLs: it’s called World Wide Web

The World Wide Web is easier to use if we have a browser thatTo browser web pages, running in a graphical user interface context.

Great efficiencies can be accomplished if we useThe Internet and the World Wide Web to conduct business.

The Creation of the Internet

The creation of the Internet solved the following challenges: Basically inventing digital networking as we know it Survivability of an infrastructure to send / receive high-speed

electronic messages Reliability of computer messaging

The Universal Resource Locator (URL)

Each page of information on the web has a unique address called theURL at which it can be found

http://faculty.uscupstate.edu/atzacheva/lecture1.html

The documentcan be obtained

using theHypertext

Transfer Protocol(HTTP)

Host Name -The Name ofWeb Server

Path to the WebPage

Denotes that the Fileis Written in HTMLHyperText Markup

Language

File Name

1 2 3

Protocol Host Name File Name

Protocols that may appear in URL’s

Protocols Names Use

ftp:// File transfer

http:// Hypertext

https:// Hypertext Secure

Mailto: Sending email

News: Requesting newstelnet:// Remote login

Much of the power of browsers is that they are multiprotocol.That is, they can retrieve and render information from a variety ofservers and sources.

Web Client/Server Architecture

The Problem Before Internet: different packet-switching networks

(e.g., ARPANET, ARPA packet radio) only nodes on the same network could communicate

A Translation-based Solution

application-layer gateways inevitable loss of some semantics difficult to deploy new internet-wide applications hard to diagnose and remedy end-to-end problems stateful gateways inhibited dynamic routing around failures

no global addressability ad-hoc, application-specific solutions

ALG

ALGALG

ALG

The Internetworking Problem

Two nodes communicating across a “network ofnetworks”… How to transport packets through this heterogeneous

mass ?

A B

Cloud

Cloud

Cloud

Declared Goal

“…both economic and technicalconsiderations lead us to prefer that theinterface be as simple and reliable aspossible and deal primarily with passing databetween networks using different packetswitching strategies”

V. G. Cerf and R. E. Kahn, 1974

The Challenge: Heterogeneity

Share resources of different packet switchingnetworks interconnect existing networks

… but, packet switching networks differ widely different services e.g., degree of reliability

different interfaces e.g., length of the packet that can be transmitted, address

format different protocols e.g., routing protocols

The Challenge: Scale

Allow universal interconnection Mantra: Connectivity is its own reward

… but, core protocols had scalability issues Routing algorithms were limited in the number of

nodes/links they could handle and were unstable after apoint

Universal addressing to go with routing As large numbers of users are multiplexed on a shared

system, a congestion control paradigm is necessary forstability

No universal, scalable naming system…

The Internetworking Problem

Problems: heterogeneity and scaling Heterogeneity: How to interconnect a large number of disparate

networks ? (lower layers) How to support a wide variety of applications ?

(upper layers) Scaling: How to support a large number of end-nodes and

applications in this interconnected network ?

Solution

Network LayerGateways

The IP Solution …

internet-layer gateways & global addresses simple, application-independent, lowest denominator

network service: best-effort datagrams stateless gateways could easily route around failures with application-specific knowledge out of gateways: NSPs no longer had monopoly on new services Internet: a platform for rapid, competitive innovation

IP

IPIP

IP

Network-layer Overlay model

Define a new protocol (IP) and map allapplications/networks to IP Require only one mapping (IP -> new protocol) when

a new protocol/app is added Global address space can be created for universal

addressibility and scaling

Before IP

No network level overlay: each newapplication has to be re-implemented forevery network technology!

Telnet FTP NFS

Packetradio

Coaxialcable

Fiberoptic

Application

TransmissionMedia

HTTP

(FTP – File Transfer Protocol, NFS – Network File Transfer, HTTP – World Wide Web protocol)

IP Key ideas: Overlay: better than anyany translation. Fewer, simpler

mappings. Network-layer: efficient implementation, global addressing

Telnet FTP NFS

Packetradio

Coaxialcable

Fiberoptic

Application

TransmissionMedia

HTTP

IntermediateLayer (IP)

Original TCP/IP (Cerf & Kahn)

No separation between transport (TCP) andnetwork (IP) layers

One common header use ports to multiplex multiple TCP connections

on the same host

Byte-based sequence number (Why?) Flow control, but not congestion control

Source/Port Source/Port Window ACK Text32 32 16 16 8n

Today’s TCP/IP

Separate transport (TCP) and network (IP)layer (why?) split the common header in: TCP and UDP

headers fragmentation reassembly done by IP

Congestion control

Addressing

How to find if destination is in the samenetwork ? IP address = network ID + host ID. Source and destination network IDs match => same

network (I.e. direct connectivity) Splitting address into multiple parts is called

hierarchical addressing

Network Host

Boundary

Converting a 32-bit Internet Address toDotted Decimal Format

An Internet address, known as an IP address for “Internet Protocol”is comprised of four binary octets, making it a 32-bit address.

IP addresses, difficult for humans to read in binary format, are oftenconverted to “dotted decimal format”

To convert the 32-bit binary address to dotted decimal format, dividethe address into four 8-bit octets and then convert each octet to adecimal number.

Each octet will have one of 256 values (0 through 255)

192.48.29.253(Example of an IP address in dotted decimal form)

Recall binary to decimal conversion

IP address conversion

Convert the following 32-bit Internet address into dotted decimal format:

01011110000101001100001111011100

1) Divide the IP address into four octets01011110000101001100001111011100

2) Convert each binary octet into a decimal number01011110 = 64+16+8+4+2 = 9400010100 = 16+4 = 2011000011 = 128+64+2+1 = 19511011100 = 128+64+16+8+4 = 220

3) Write out the decimal values separated by periods94.20.195.220

The Internet Network layerThis image cannot currently be displayed.

routingtable

Host, router network layer functions:

Routing protocols•path selection•RIP, OSPF, BGP

IP protocol•addressing conventions•datagram format•packet handling conventions

ICMP protocol•error reporting•router “signaling”

Transport layer: TCP, UDP

Link layer

physical layer

Networklayer

IP Addressing: introduction

IP address: 32-bit identifier forhost, router interface

Interface: connection betweenhost, router and physical link router’s typically have

multiple interfaces host may have multiple

interfaces IP addresses associated with

interface, not host, router Hosts in the same network have

same network ID

223.1.1.1

223.1.1.2

223.1.1.3

223.1.1.4 223.1.2.9

223.1.2.2

223.1.2.1

223.1.3.2223.1.3.1

223.1.3.27

223.1.1.1 = 11011111 00000001 00000001 00000001

223 1 11

IP Address Classes

There are 5 different classes of IP addresses: A, B, C, D and E. A, B, and C are available for commercial use For example, a Class A network could support 126 networks,

each with 16,777,216 hosts

Subnet Addressing

Classful addressing inefficient: Everyone wants class B addresses Can we split class A, B addresses spaces and accommodate more

networks ? Need another level of hierarchy. Defined by “subnet mask”,

which in general specifies the sets of bits belonging to thenetwork address and host address respectively

Network Host

Boundary is flexible, and defined by subnet mask

The Domain Name System

We would go crazy if we would have to remember the IPaddresses of all the web sites that we wanted to visit

The Domain Name System translates between domain namesand IP addresses of devices connected to the Internet– A domain name (a part of the URL) is a unique alphanumeric

name such as gmu.edu– The top level domain name is edu and the secondary level

domain name is gmu in the above example (there could beup to 127 levels, but more than 4 is rare)

Examples of top level domains

Generic top level domains .com .biz .info .edu .mil .net, etc.

Country codes (2 character codes) .jp, .sw, .us, etc.

DNS

IP ADDRESSES DOMAIN NAMESEvery device connectedhas a unique 32-bitaddress

Machine Readablee.g. 151.196.19.22

DNS

Translation Betweendomain Names and IP

Addresses

Every deviceconnected has analphanumericaddress

IP address and domain name allocation requires central administration toavoid duplication Previously administered by U.S. government contract (NSI) In 1998, technical coordination assigned to ICANN (Internet Corporation forAssigned Names and Numbers).

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