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Introduction to Information Technology LECTURE 10 THE INTERNET AND TCP/IP IT 101 Section 3 Department of Electrical and Computer Engineering
Internet Topics The Internet • Overview • Brief History • Internet Applications • Technical Architecture • Backbone • Routing Fundamentals • ISPs • Access • TCP/IP • Internet Addressing Issues • The Domain Name System • Management and Administration
Unintended Consequences of the Internet? Addiction Viruses Security Threats • 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. Spam Fraud
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)
Some Internet History Inception in the late 1960s • 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
Internet History Milestones 1993 Web Browser “Mosaic” invented by Mark Andreesen 1985 NSFNET founded by The National Science Foundation 1969 ARPANET R&D Project 1983 DOD Mandated Adoption of TCP/IP ARPANET INTERNET 1974 Vinton Cerf and Robert Kahn Initiated TCP/IP What Milestones in Last Ten Years? 1983 ARPANET Split into ARPANET and MILNET 1991 World Wide Web Released by Tim-Berners Lee
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
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?
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
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.
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 File Name Denotes that the File is Written in HTML HyperText Markup Language
The Internet comprises a complex system of hierarchical access providers
The Internet(Diverse Telecom Technologies Integrated by a Common Protocol)
Router • Connects 2 or more networks and uses network layer addresses (like IP address) to make data forwarding decisions Workstation A Workstation B Higher Layers Higher Layers Router Network 18.104.22.168 Network 22.214.171.124 Network Network Data Link Data Link Data Link Data Link Physical Physical Physical 1 Physical 2
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
Accessing the Internet: “The Last Mile” INTERNET SERVICE PROVIDER ROUTER -Leased Line -Frame Relay Business Wireless ISP DIAL-UP Via Modem Cable Modem xDSL Home or Mobile User
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)
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
The IP Address • Unique 32-bit (4 byte) logical address • 126.96.36.199 (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
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 :
Converting a 32-bit Internet Address to Dotted Decimal Format Recall binary to decimal conversion from Lecture 2 • 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) 188.8.131.52 (Example of an IP address in dotted decimal form)
Internet Address Example Convert the following 32-bit Internet address into dotted decimal format: 01011110000101001100001111011100 1) Divide the IP address into four octets 01011110 00010100 11000011 11011100 2) Convert each binary octet into a decimal number 01011110 = 64+16+8+4+2 = 94 00010100 = 16+4 = 20 11000011 = 128+64+2+1 = 195 11011100 = 128+64+16+8+4 = 220 3) Write out the decimal values separated by periods 184.108.40.206
Believe it or Not: We’re Running Out of IP Addresses! IPv4 to IPv6 • 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.
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
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.
The Domain Name System IP ADDRESSES DOMAIN NAMES Every device connection has a unique 32-bit address Human Readable cnn.com DNS Translation Between Host Names and IP Addresses Every device connection has an alphanumeric address Machine Readable e.g. 220.127.116.11 • 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).
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
Some Issues to Consider The Internet has become socio-economically very important, bringing up many issues of control and security. • 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?
Network Security Issues • Confidentiality • Integrity • Authenticity DENIAL OF SERVICE ATTACKS Cyber-Surveillance Site Security (Because LAN sniffing is easy) PASSWORD THEFT PUBLIC INTERNET PRIVATE NETWORK IDENTITY THEFT VIRUSES INFRASTRUCTURE ATTACKS Firewall DATA INTERCEPTION Authentication (e.g. SecureID) Encryption DATA DISRUPTION OR MODIFICATION
Who is the Threat? Hackers and Crackers and Terrorists • 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
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
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.
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