Post on 27-Dec-2015
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710: Foundations of Information Systems
Chapter 4: TelecommunicationsAnd Networks
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Telecommunication Systems
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Transmission Media
• Twisted-Pair Wire– Telephone wire, Cat 5
• Coaxial Cable– Cable TV cable
• Fiber-Optic Cable– 20 x price of twisted pair,
1000 x capacity
• Microwave Signals– ’No, you don’t get toasted!’– Satellites, line-of-sight
• Infrared and Radio Signals– Wireless, short distance
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Media Types
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Data Processing Strategies
• Centralized Processing– all processing occurs in a single location
or facility• Decentralized Processing
– processing devices are placed at various remote locations
• Distributed Processing– computers are placed at remote
locations and connected via telecommunication devices
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Terminal-to-Host Connection
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File Server Connection
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Client/Server Connection
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Client/Server Processing• Cooperation Through Message
Exchange
– Client program sends Request message, such as a database retrieval request
– Server program sends a Response message to deliver the requested information or an explanation for failure
Client Machine Server
Client ProgramServer
Program
Request
Response
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Networks
• Local Area Network (LAN)– Connect computers in a single building or
campus– Distances typically less than 1,000 meters
• Wide Area Networks (WAN)– Connects computers across long distances– Typically several hundred kilometers– Example: Internet
• Metropolitan Area Networks (MAN)– Connects computers in the same city– Up to 100 kilometers (often much less)
Not in Book
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Network Types
• Ethernet– Very popular, Cheap 10/100/1000 Mbps– Usually short distances
• Asynchronous Transfer Mode (ATM)– Good for multimedia. Used for Internet access. – Up to 622 Mbps over long distances
• Bluetooth– For connecting devices (printer, mouse etc) to
PC. Short range, piconet, Max 1 Mbps
• More wireless on next slide...
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Wireless alphabet soup
Spec Range Speed Frequency
802.11b(WiFi)
75 m 11 Mbps 2.4 GHzRisks interference w/ cordless phones
802.11a(WiFi-5)
30 m 54 Mbps 5 GHzLess interference
802.11g 75 m 54 Mbps 2.4 GHzBackwards compatible w/802.11b
• 802.11i – security standard (authentication and encryption)• 802.1x – authentication
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The Internet
Traffic travels across routers between LANs
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Technological Underpinnings• Internet Management
– No owner! Managed by negotiation and non-binding contracts. May not continue to work.
– Internet Engineering Task Force (www.ietf.org) decides on technical standards
– World Wide Web Consortium (www.w3c.org) sets HTML and HTTP standards
• Backbone network (gigabit connection)– Check
http://global.mci.com/about/network/global_presence/global/ (just one company)
– Or: http://www.caida.org/tools/visualization/mapnet/Backbones/
• Network Addressing– IP numbers: e.g. 140.252.13.33 (32 bits = 4 billion
addresses)– The internet is running out of addresses!– Long-term solution: IP v6 (128 bits = 3.4 * 1038 addresses)
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More Technology…
• Domain Names– Text version of IP address (translated by DNS)– Country domains (.dk, .uk, .de, .us) and
generic domains (.com, .net, .org). USA also has .mil, .gov, and .edu.
– NEW: .aero, .biz, .coop, .info, .museum, .pro, .name
– Managed by ICANN (www.icann.org)
• Network Access– No-one controls access!– Most people connect through an ISP
• AOL and MSN largest ISPs (even though they are Online Services (OLSs)
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Internet Protocols
• Internet Protocol (IP): standard that enables traffic to be routed from one network to another as needed
• Transport Control Protocol (TCP): rules that computers on a network use to establish and break connections
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Internet Communication• E-mail (first time in
1971!)– One of the most popular
activities on the Internet!– Becoming official
business communication mode
– ListServ (http://www.lsoft.com/lists/listref.html)
• Newsgroups (Usenet)– Go to
http://www.google.com/grphp?hl=en
– Being outpaced by web-based fora
• Telnet• FTP
• Streaming– Internet Radio, Internet
TV• Real-Time Streaming
– Videoconferencing• Chatting/IM• Online collaboration• Internet Telephony
(VoIP)• Web log (blog)• Rich Site Summary
(RSS) – a.k.a. RDF Site Summary
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World Wide Web (www)• Hyper Text Transfer Protocol (HTTP)• Hyper Text Markup Language (HTML)
– And derivatives/alternatives• SGML, DHTML, XML
• URL• Browser• Search engines
– Google most popular– Categories: Web crawlers (e.g. Google), categorized (e.g.
Yahoo), Meta-search (search many engines)– Info on search engines: www.searchenginewatch.com
• Review Question: What’s the difference between the Internet and the Web?
http://www.uwosh.edu
Developed in 1989
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Internet Worldwide Trends
• Rapid worldwide growth continues• Main use in
– North America, Europe, Australia
• Some use in– Asia, Middle East, Eastern Europe, South America
• Virtually no use– Africa (90% in South Africa)
• 80% of all international connections from Asia, Africa, S. America go directly to a US city
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Worldwide Trends
• Online Population in million vs. World Population– Online: Jan. 2000 and Feb. 2002, Offline:
Mid-2000
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Intranets and Extranets
• Intranet– An internal corporate network
built using Internet and World Wide Web standards and products; used by the employees of the organization to access corporate information.
• Extranet– A network that links selected
resources of the intranet of a company with its customers, suppliers, or other business partners; based on Web technologies.
• Accessed by on-site employees
• Passwords needed
• Most company info can be put on intranet
• Accessed by off-site employees and business partners
• Passwords needed
• Example: Online banking, TitanWeb
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Intranet and Extranet• Both use internet
standards– Web pages, HTTP-
protocol
• Intranet– Within a company
• Extranet– Outside access to a
company’s intranet or specific web pages
– Security: Virtual Private Networks (VPN)
– Examples: TitanWeb, Online Banking, E-procurement systems
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Electronic Data Interchange (EDI)
• A system to electronically transfer business documents– Orders, bills, confirmations etc– ’Structured e-mail messages’
• Agreements/partnerships are set up in advance
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Issues in EDI
• Data Standards– ANSI X.12: Used in the US– EDIFACT: Defined by UN. Used in much of the
rest of the world– XML/EDI may help in the future
• http://www.geocities.com/WallStreet/Floor/5815/
– Companies must use the same standard to communicate
– Standards can be tailored to fit industries or individual businesses
• Mostly for large companies– May force smaller business partners to use
EDI
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Issues in EDI
• Two Network Standards• Value Added Network (VAN)
– Pro: High security, high capacity– Con: Price, incompatible hardware,
only large companies
• Internet– Pro: Cheap, ubiqutous, easy to use– Con: Security, capacity
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Virtual Private Network
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Encryption
Very important in E-commerce
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Next Week
• Lecture– Chapter 5 and 6: E-commerce, Transaction
Processing Systems, Management Information Systems, and ERP
• Presentations– Teams 1, 2 and 3
• Assignments– Assignment 2 due from Teams 4 - 8