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Introduction to Information Technology

LECTURE 10THE INTERNET AND TCP/IP

IT 101 Section 3Department of Electrical and Computer Engineering

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Internet Topics

Overview Brief History Internet Applications Technical Architecture

Backbone Routing Fundamentals ISPs Access

TCP/IP Internet Addressing Issues The Domain Name System Management and Administration

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Unintended Consequences of the Internet?

Spam accounts for roughly 60 percent of all e-mail, up from 18 percent 18 months ago.

In 1995, the number of hacking or computer attacks reported to the CERT Coordination Center for cybersecurity was 2,412. In the first three quarters of last year, the number was 114,855. In many cases, each attack affected hundreds of thousands of machines.

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What is the Internet? A Network of Networks A Wide Area Network Spanning the Globe Interconnects Millions Upon Millions of Users

Businesses Citizens Governments Academic Institutions Research Centers Libraries Etc. Etc.

Provides a Common Communications System for Diverse Computing and Network Environments

Still Rapidly Expanding Involves Numerous Technologies (Not a Single Technology)

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Some Internet History

The Internet is not a recent phenomenon - it began in the late 1960s The United States military played a major role in its development Originally called “ARPANET” ARPA = Advanced Research Projects Agency

A small U.S. Department of Defense (DOD) agency Founded in 1958 after the Soviet Union launched “Sputnik” Mission to conduct advanced defense research

The computing context in the 1960s: Computers not widely used Computers were technically incompatible Communication between computers was almost non-existent

Original purpose of ARPANET was to interconnect geographically dispersed and technically disparate computers at university research centers

Inception in the late 1960s

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Internet History Milestones

ARPANET INTERNET

1969 ARPANET

R&D Project

1991World Wide Web

Released by Tim-Berners Lee

1974Vinton Cerf

and Robert Kahn Initiated TCP/IP

1983DOD Mandated

Adoption of TCP/IP

1983ARPANET Split into ARPANET and MILNET

1985NSFNET founded by The National

Science Foundation

1993Web Browser

“Mosaic” invented by Mark

Andreesen

What Milestones in Last Ten Years?

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Internet Applications Most popular Internet applications are (not in any order):

Electronic Mail Store and forward concept Doesn’t require an immediate connection

Instant Messaging Requires concurrent online presence (Near Real Time)

The World Wide Web (and Web browsers) The “killer app” that spurred explosive Internet growth

File Sharing Distributed file sharing of MP3 and other files

Electronic Commerce Real Time Applications

Internet Telephony Internet Radio Interactive Gaming

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Emerging Internet Application: VoIP

As we’ve discussed, voice calls over the Internet are becoming commonplace.

IBM recently announced plans to migrate most of its 300,000 employees to voice over IP phone systems by 2008!

What will happen to the traditional telephone system and to local phone companies?

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Origins of the Web

Attributed to Oxford graduate Tim Berners-Lee of the European Laboratory for Particle Physics (CERN) in Geneva, Switzerland

Now the director of the W3C (World Wide Web Consortium) The Web was developed originally to solve a very specific problem

Facilitate communications among nuclear physicists located throughout the world

Share data gathered at specialized facilities (e.g. CERN and Los Alamos National Labs in the U.S.)

Web browser, Mosaic, developed in the early 1990s The National Center for Supercomputing Applications (NCSA) at

the University of Illinois at Urbana-Champaign Funded by National Science Foundation Lead programmer was Marc Andreesen, who founded Netscape

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The World Wide Web

A sophisticated system for universal information capture and delivery

Provides information access in ways not previously possible Hyperlinked (Hypertext) Graphical user interface Pictorial and non-text information Information that changes rapidly Immediate access Anyone can author a web site Multi-user access to the same information (try that with a book) Searchable information

Internet Search Engines play a critical role Google, Dogpile, Yahoo, etc.

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The Universal Resource Locator (URL)

Uniform (or Universal) Resource Locators (URLs) are unique addresses assigned to each web site.

http://www.ece.gmu.edu/ececourses/it101/prah.html

The document can be obtained using

the Hypertext Transfer Protocol

(HTTP)

Host Name - The

Name of the Server User Defined

Path/Directory to the Web

Page Denotes that the File is Written in

HTMLHyperText Markup

Language

File Name

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Web Client/Server Architecture

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The Internet comprises a complex system of hierarchical access providers

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The Internet(Diverse Telecom Technologies Integrated by a Common Protocol)

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Router Connects 2 or more networks and uses network layer

addresses (like IP address) to make data forwarding decisions

HigherLayers

Physical

HigherLayers

PhysicalPhysical 1

Router

Data Link

Physical 2

Data Link Data Link

Workstation A Workstation B

Data Link

Network145.65.23.102

Network137.22.144.6 Network Network

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Network Access Points

Backbone networks come together at major switching points called “Network Access Points” (NAPs) For example:

MAE-East (Washington, DC) MAE-West (San Francisco) Chicago, Houston, LA, New York, Dallas Various international locations

ISPs interface to the Internet at Network Access Points

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Accessing the Internet: “The Last Mile”

ROUTER-Leased Line-Frame Relay

INTERNET SERVICE

PROVIDER

INTERNET SERVICE

PROVIDER

Business

Home or Mobile User

ISPISPDIAL-UP Via Modem

Cable Modem

xDSL

Wireless

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DSL - Digital Subscriber Line Data and voice can share the same line Uses existing wire lines

Low end of wire bandwidth is used for voice Upper end of wire bandwidth is used for data

Forms of DSL Asynchronous DSL (ADSL) different speeds up and downstream High-bit rate DSL (HDSL) same speed up and downstream Very-high data rate DSL (VDSL) different speeds up and

downstream (but up to 50 Mbps) DSL Issues:

Availability of xDSL service Cost Wire condition (customers may experience lower data rates than

advertised)

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Addressing Schemes

Three addressing schemes are used in sending information across the Internet

Organizationally-Unique Identifier (OUI) This is the 48-bit address stamped on Network Interface

Cards… no two devices have the same address IP Address

The 32-bit address used to identify an “attachment” to the Internet (port, NIC, logical address, etc.)

Domain Name System Hierarchical, alphanumeric addressing scheme that is a

“synonym” of an IP address

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The IP Address

Unique 32-bit (4 byte) logical address 129.174.1.8 (This one belongs to GMU)

Made up of two parts Network Number

Identifies a network Must be assigned by the Internet Network Information

Center (InterNIC) Host Number

Identifies a host on a network Assigned by the local network administrator

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The IP Address

There are 5 different classes of address (you can tell by the first octet)

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 :

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IP Address Classes

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Converting a 32-bit Internet Address to Dotted 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 often converted to “dotted decimal format.”

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

Each octet will have one of 256 values (0 through 255) 192.48.29.253192.48.29.253

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

Recall binary to decimal conversion from Lecture 2

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Internet Address Example

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

0101111000010100110000111101110001011110000101001100001111011100

1) Divide the IP address into four octets01011110 01011110 00010100 00010100 11000011 11000011 1101110011011100

2) Convert each binary octet into a decimal number2) Convert each binary octet into a decimal number01011110 = 64+16+8+4+2 = 9401011110 = 64+16+8+4+2 = 9400010100 = 16+4 = 2000010100 = 16+4 = 2011000011 = 128+64+2+1 = 19511000011 = 128+64+2+1 = 19511011100 = 128+64+16+8+4 = 220 11011100 = 128+64+16+8+4 = 220

3) Write out the decimal values separated by periods3) Write out the decimal values separated by periods94.20.195.22094.20.195.220

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Believe it or Not: We’re Running Out of IP Addresses!

The number of IP addresses provided by a 32-bit code (IPv4) is insufficient for the Internet’s current growth trajectory.

How many different addresses does a 32-bit number provide? 232 = 4,294,967,296

How can we be running short? Rapid global diffusion Rapid proliferation of wireless devices that require an IP

address Voice over IP will only increase the shortage

Is there a solution? IPv6 is going to increase the address space to 128 bits How many addresses will that provide?

Short term work-arounds like Network Address Translation have helped stall the need to migrate to IPv6, but the transition is forthcoming.

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TCP/IP

TCP/IP consists of two different protocols

IP is a connectionless protocol that provides addressing services to a datagram flowing across the network (IP operates at the Network layer [Layer 3])

In other words, IP just puts an address and sends the datagram off into the darkness and doesn’t care if it arrives at the destination

TCP is a connection oriented protocol that provides transmission services over a session (TCP operates at the Transport layer [Layer 4])

Manages a connection for flow control

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The Domain Name System

Translates between domain names and IP addresses of devices connected to the Internet.

A domain name is a unique alphanumeric name such as gmu.edu

Top level domains - address suffixes Generic top level domains

.com .biz .info .edu .mil .net, etc.

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

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The Domain Name System

IP ADDRESSES DOMAIN NAMES

Every device connection has a unique 32-bit address

Machine Readablee.g. 151.196.19.22

DNS

Translation Between Host Names and IP Addresses

Every device connection has an alphanumeric address

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

Human Readable cnn.com

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Setting Internet Standards

IETF - Internet Engineering Task Force www.ietf.org Examples of standards work - IPv4 and IPv6

W3C - World Wide Web Consortium www.w3c.org Created in October, 1994 Examples of standards work - HTML, XML

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Some Issues to Consider

If the global Internet is really global, who’s in control? Who makes decisions about domain name disputes? Should online sales be taxed? By whom? What are the ramifications of the global digital divide? How are political and religious forces inhibiting access? Should governments be responsible for security and critical

infrastructure protection? Could a terrorist attack disable the Internet?

The Internet has become socio-economically very important, bringing up many issues of control and security.

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Network Security Issues

Site Security(Because LAN sniffing is easy)

Authentication (e.g. SecureID)

Firewall

PRIVATE

NETWORK

PRIVATE

NETWORK

PUBLIC INTERNET

PUBLIC INTERNET

Encryption

Cyber-Surveillance

INFRASTRUCTURE ATTACKS

PASSWORD THEFT

VIRUSES

DENIAL OF SERVICE ATTACKS

DATA INTERCEPTION

Confidentiality Integrity Authenticity

IDENTITY THEFT

DATA DISRUPTION OR MODIFICATION

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Who is the Threat?

Hackers take advantage of weaknesses in systems to gain unauthorized access

Some may have a specific target or perhaps hack for the challenge

Crackers are what hackers call people who maliciously attack systems for such reasons as:

Terrorism Corporate Espionage System Sabotage Personal Attacks Fraud Financial Crimes

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What are the Threats?

Viruses Trojan Horse Attacks Infrastructure Attacks Bandwidth Theft Data Interception Password Theft (or Password

Guessing) Identity Theft Data Disruption or Modification Denial of Service Attacks

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What’s a Denial of Service Attack?

Cripples the attacked system by flooding it with a huge number of requests that consume system resources.

Can crush an Internet site. Most effective kind is a “distributed denial of service attack”

that uses hundreds or thousands of computers to unknowingly participate in the attack.

EASY TO DO.. HARD TO PREVENT Difficult to prevent or stop because it can be accomplished

without privileges on the attacked system

Serious Denial of Service attacks have been made against many of the Internet DNS root servers.

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Security Services

Privacy: Preventing unauthorized viewing of data Encryption

Authentication: Positively identifying an object or identity Token (a thing you have) - Discuss SecureID in class PIN (a thing you know) Biometrics (a thing you are)

Access Control: Restricting access to data or services Passwords, software policies, physical security Firewalls--prevent outsiders from accessing an internal network,

or insiders from accessing unauthorized external sites—can be a router

Integrity: Data integrity ensures the data received was the data sent Digital signatures place a digital “watermark” on data that

ensures no information is altered

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More Discussion about Internet Security