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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