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					   Communication Networks
           Laudon & Laudon
           chapter 6
   Additional Reading:
           Brien & Marakas
           chapter 6

COMP 5131                    1
     Telecommunication and Networking
        Current Trends
        Computer Network

     Key Digital Networking Technologies
     Communication Network Topologies
     The Global Internet
        Addressing and Architecture
        Future Trends

     Internet and E-commerce
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Hyatt Hotels – Wireless Networking
      500 Guest Rooms, 28 floors
      Distance from central Osaka

      Pressures to adapt in a
      competitive industry
      Outdated communication methods

      Implement a mobile wireless LAN
      to provide integrated voice and data
      coverage across the entire hotel
      Wireless Handheld or Notebook PCs → Ability to access the info online anywhere
      in hotel and respond accurately and immediately
      Provide immediate/before service from past record, memorable service
      Savings → 60 hrs per year per staff member or total 4800 hrs annually
      Intel Centrino and Intel XScale technologies capable of handling phone calls as
      well as data communication allowed employees to access information from
      anywhere in the hotel
      Demonstrates IT’s role in hastening the communication and flow of information
      Illustrates digital technology’s role contemporary networking
COMP 5131                                                                               3
Trends – Networking and Telecom
      Telephone Networks and Computer Networks
            Single digital network using Internet standards
      Cable companies providing voice service

      More than 60% U.S. Internet users → Broadband
      Cost of Service ↓

  Broadband Wireless
      Voice and data communication as well as Internet access are
      increasingly taking place over broadband wireless platforms
            Mobile Wireless Access → Fastest growing form of internet access (2008 – 96% ↑)

COMP 5131                                                                                     4
Trends – Networking and Telecom
      Next generation of the Internet – Network of Networks
      1996 to 2006
      High-performance backbone network – different infrastructure
            BW → 2.5 - 9.6 Gbps
      200 universities, scientific institutions, communications corporations →
      Part of Internet2
      Never, Not intended to replace Internet, test bed
      Purpose → Develop roadmap, next stage of innovation for current internet
      New addressing protocol, satellite quality video
      Most Connections → Abilene
            Network backbone, 10 Gbps
      Video Conferencing, Multicasting, Remote Applications, Speed ↑ & BW ↑

      Internet population growth, Out of available IP address – 2013
      New version, 128 bit addresses, more than new quadrillion (2^128)
      possible addresses, IPv4 – 32bits
      Roughly 5,000 addresses for every square micrometer of the earth's
      surface, sufficiently large for the indefinite future
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Network Concept
      An interconnected chain, group or system

  Number of possible connections (N → Nodes)
            If 10 computers on a network → 10 * 9 = 90 possible connections

  Metcalfe’s Law
      The usefulness of a network equals the square of number of users
      On a small network, a change in technology affects technology only
      On a large network like the Internet, a change in technology affects
      social, political and economic systems

COMP 5131                                                                     6
Computer Network
   Two or More Connected Computers
   Major Components in Simple Network
      Client computer
      Server computer
      Network interfaces (NICs)
      Connection medium
      Network operating system
            Routes & manages communication on network
            Coordinates network resources
            Example → Server software’s, Novell NetWare, Linux, Microsoft Windows Server
            Sends packet of data to all connected devices
            More intelligence, can filter and forward data to specified destination on network

      Device used to route packets of data through different networks,
      ensuring that data sent gets to the correct address
COMP 5131                                                                                        7
Computer Network
      Makes connections between telecommunications
      circuits in a network
      Intelligent communications processor that
      interconnects networks based on different protocols
      Connects networks using different communications
      Connection medium

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Computer Network
      Makes connections between telecommunications
      circuits in a network
      Intelligent communications processor that
      interconnects networks based on different protocols
      Connects networks using different communications
      Connection medium

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Network in Large Companies
   Can Include
      Hundreds of local area networks (LANs) linked to
      firmwide corporate network
      Various powerful servers
            Web site
            Corporate intranet, extranet
            Backend systems
      Mobile wireless LANs (Wi-Fi networks)
      Videoconferencing system
      Telephone network
      Wireless cell phones

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Network in Large Companies

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Key Network Technologies
   Client/Server Computing
      Clients → End user personal computers or networked
      Servers → Manage Networks
      Interconnected by LANs, Distributed computing model
      Processing shared between clients and servers
      Server sets rules of communication for network and
      provides every client with an address so others can
      find it on the network
      Has largely replaced centralized mainframe
      The Internet → Largest implementation of client/server

COMP 5131                                                  12
Key Network Technologies
   Packet Switching
      Method of slicing digital messages into parcels (packets)
      Sends packets along different communication paths as
      they become available, and then reassembling packets
      at destination
      Previous circuit-switched networks required assembly
      of complete point-to-point circuit
            Expensive, Wasted communication capacity
      Packet switching more efficient use of network’s
      communications capacit

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Key Network Technologies
   Packet Switching Communication

Data are grouped into small packets, transmitted independently over various Communications channels
Reassembled at their final destination

COMP 5131                                                                                     14
Computer Network
   Network Topologies (Structure of Network)
      Star → ties end user computers to a central computer
      Ring → ties local computer processors together in a
      ring on a relatively equal basis
      Bus → local processors share the same comm channel

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Key Network Technologies
   Open Systems Interconnection Model (OSI)
      A seven-layer model that serves as a standard model for network
      Model for how messages should be transmitted between two points in a
      Each layer adds functions

   TCP/IP and Connectivity
      Connectivity between computers enabled by protocols
      Protocols → Different components in network communicate with each
      other by adhering to common set of rules
      Transmission Control Protocol/Internet Protocol
            Common worldwide standard that is basis for Internet
            TCP → Movement of data between computes, establish connection, sequences
            transfer of packets, acknowledges packet sent
            IP → Responsible for delivery of packets, disassembling and reassembling of

      A five layer telecommunications protocol used by the Internet

COMP 5131                                                                          16
Key Network Technologies
   OSI (7 layer) Communication Network
   TCP/IP (5 layer)

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Key Network Technologies
      Postal system → finds your house addresses, delivers your mail
      IP4 → Current IP addressing protocol, 32 bit Internet address value
      First Part identifies the network on which the host resides
      Second part identifies the particular host on network
      Four decimal numbers separated by period
      Valid addresses can range from to (4.3
      billion addresses)

COMP 5131                                                             18
Key Network Technologies
   TCP/IP (IP4)

      Class E addresses Reserved → Research Organizations, Experiments
      Limited broadcast address →
            One sender to many recipients, all the nodes on LAN
      Loopback IP address →, Adapter intercepts and sends back to
      application, network behavior
      Private Addresses (reserved range for intranet, free usage)

COMP 5131                                                                19
Key Network Technologies
      128 bit address
      Generally written in hhhh:hhhh:hhhh:hhhh:hhhh:hhhh:hhhh:hhhh
      Shorthand Notation → E3D7::51F4:9BC8:C0A8:6420
      Mixed Notation → E3D7::51F4:9BC8:
      Only two reserved addresses in IPv6
         0:0:0:0:0:0:0 → Internal for protocol implementation
         0:0:0:0:0:0:1 → Loopback address (similar to in IPv4)

COMP 5131                                                                  20
Key Network Technologies
      Over 46 million servers (2004)
      710 – 945 million users (2004)
      No central computer system
      No governing body
      No one owns it

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The Global Internet
   What is Internet?
   Internet Addressing and Architecture
       The Domain Name System
            Hierarchical structure
            Top-level domains

   Internet Architecture and Governance
       No One Owns Internet!
       Worldwide Internet Policies → Professional & Government Bodies
            IAB, ICANN, W3C

COMP 5131                                                               22
The Global Internet
      Domain Name System

The Domain Name System is a hierarchical system with a root domain, top-level domains, second-level domains, and host computers at the third level.

COMP 5131                                                                                                                                     23
The Global Internet
   Internet Services
       Chatting and instant messaging
       File Transfer Protocol (FTP)
       World Wide Web
       Virtual private network (VPN)

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The Global Internet
      Client/Server Computing on Internet

Client computers running Web browser and other software can access an array of services on servers
over the Internet. These services may all run on a single server or on multiple specialized servers.

COMP 5131                                                                                              25
The Global Internet
   How Voice over IP Works?

 An VoIP phone call digitizes and breaks up a voice message into data packets that may travel along different routes before being
 reassembled at the final destination. A processor nearest the call’s destination, called a gateway, arranges the packets in the proper order
 and directs them to the telephone number of the receiver or the IP address of the receiving computer.

COMP 5131                                                                                                                                       26
Virtual Private Network
  A secure network that uses the Internet as its backbone
  but relies on firewalls, encryption and other security
  A pipe traveling through the Internet

COMP 5131                                                   27
The Global Internet
    Virtual Private Network Using Internet

  This VPN is a private network of computers linked using a secure “tunnel” connection over the Internet. It protects data transmitted
  over the public Internet by encoding the data and “wrapping” them within the Internet Protocol (IP). By adding a wrapper around a
  network message to hide its content, organizations can create a private connection that travels through the public Internet.

COMP 5131                                                                                                                                28
Network Computing
  Thin Clients
    Network computers and other clients provide a
    browser-based user interface

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Case Study – Monitoring Employees
People Monitoring Employees on Networks: Unethical or Good Business?
   Question - Should managers monitor employee e-mail and Internet usage?
   Why or why not?

      Corporate misuse, abuse of email for personal reasons is exploding
      Employees who use company resources for work not related to the company are,
      in essence, engaged in “service theft.”
      Companies are in business to generate profits for their shareholders. Managers
      certainly should be concerned with the loss of time and employee productivity, the
      additional traffic it creates on their networks that inhibits the efficiency for real
      business purposes, lost revenue or missed opportunities, as well as overcharging
      clients because of lost employee efficiencies.
      The company itself is responsible for the use of its resources and what
      employees do while using them
      Adverse publicity can seriously affect a company and could even result in very
      expensive lawsuits
      Companies also fear e-mail leakage of trade secrets. Other legal and regulatory
      problems involve the safe keeping of all e-mails that are generated on corporate
      equipment. This information must be retained for specific time periods and may
      be requested as evidence in a lawsuit

COMP 5131                                                                                30
Case Study – Monitoring Employees
  Describe an effective e-mail and Web use policy for a company
      Effective e-mail and Web use policy must be carefully designed
      and clearly communicated to all persons who use these corporate

      There are a number of different policies - Some companies allow
      absolutely no personal use of corporate networks whereas others
      allow some degree of activity that is easily monitored

      A good policy will detail exactly what type of activity is acceptable
      and what is not allowed

      Clearly articulate sanctions that will be followed for any and all
      offenses in relation to the policy

      Most of all, rules for Internet usage should be tailored to specific
      business needs and organizational cultures
COMP 5131                                                                    31
Case Study – Monitoring Employees
  Explore the Web site of online employee monitoring software such as SpectorSoft, NetVizor, SpyTech, or
  Activity Monitor and answer the following questions

  What employee activities does this software track? What can
  an employer learn about an employee by using this software?

       SpectorSoft Web site - The Spector Pro keylogger will instantly
       inform you whenever they type, or even simply view, any alert
       words or phrases that you specify

       Spector Pro continuously looks for alert words in everything they
       type, every web site they visit, all chats/Instant Messages and in
       each email sent or received. Every time a keyword is detected,
       Spector Pro will immediately email you a detailed report of when,
       where and how the keyword was used

COMP 5131                                                                                                  32
Case Study – Monitoring Employees
  How can businesses benefit from using this software?
      Testimonials → With Spector Pro, we were immediately able to
      discover which employees were non-productive. Not only has
      Spector Pro helped us weed out lazy workers, it also helped to
      uncover fraud in some of our departments

      In addition, this program has also allowed us to realize and
      resolve training issues we've experienced with our internal

      Spector Pro is very stealthy, has no noticeable effect on system
      performance and provides excellent return on investment

COMP 5131                                                                33
World Wide Web
  Hypertext Markup Language (HTML):
      Formats documents for display on Web

  Hypertext Transfer Protocol (HTTP):
      Communications standard used for transferring Web pages

  Uniform resource locators (URLs):
      Addresses of Web pages
            Example →

  Web servers
            Software for locating and managing Web pages

COMP 5131                                                                34
World Wide Web
  Search Engines
      Started in early 1990s as relatively simple software programs using
      keyword indexes
      In 1994 two Stanford students → Hand selected list of web pages
            Yet Another Hierarchical Officious Oracle – Yahoo!
      In 1998, two another Stanford students released first version of Google
            Not only index each page’s word but also ranked search results → PageRank
            Also combination of key words → Foundation of Google
      Major source of Internet advertising revenue via search engine marketing,
      using complex algorithms and page ranking techniques to locate results
  Shopping Bots
      Use intelligent agent software for searching Internet for shopping
      MySimon or Google Product Search
            Filter and retrieve info about products of interest, negotiate price/delivery
            terms, evaluate competitive products using criteria

  Semantic Web
      Collaborative effort to make Web searching more efficient by reducing the
      amount of human involvement in searching for and processing Web
COMP 5131                                                                                   35
World Wide Web
   How Google Works?

The Google search engine is continuously crawling the Web, indexing the content of each page, calculating
its popularity, and storing the pages so that it can respond quickly to user requests to see a page. The entire
process takes about one-half second.

COMP 5131                                                                                                         36
World Wide Web
      Major Web Search Engines

Google is the most popular search engine on the Web, handling 56 percent of all Web searches.

 COMP 5131                                                                                      37
World Wide Web
  Web 2.0
      Started in early 1990s as relatively simple software programs
      using keyword indexes

      Second-generation interactive Internet-based services for people
      to collaborate, share information, and create new services online

      Blogs → Chronological, informal Web sites created by individuals
      using easy-to-use weblog publishing tools

      RSS (Really Simple Syndication) → Syndicates Web content so
      aggregator software can pull content for use in another setting or
      viewing later, mashups

      Wikis → Collaborative web sites where visitors can add, delete, or
      modify content on the site

COMP 5131                                                             38
The Global Internet
      Use existing network infrastructure with Internet
      connectivity standards software developed for the Web
      Create networked applications that can run on many
      types of computers
      Protected by firewalls

      Allow authorized vendors and customers access to an
      internal intranet
      Used for collaboration
      Also subject to firewall protection

COMP 5131                                                39
The Wireless Revolution
  Wireless Devices
      PDAs, BlackBerry, smart phones
      Instant availability of Info from field – Inventory level ↓

  Cellular Systems
      Competing standards for cellular service
            United States → CDMA
            Most of rest of world → GSM
      Third-generation (3G) networks
            Higher transmission speeds suitable for broadband Internet
            384 Kbps (Mobile), 2Mbps (Stationary), Available in HK, Japan,
            S. Korea, Taiwan, Singapore, N. Europe, Not yet in USA(?)

COMP 5131                                                              40
The Wireless Revolution
  Bluetooth Network (PAN)
      Short-range wireless technology
      To connect PC to peripherals such as printer
            Within a small 30-foot (10-meter) area

COMP 5131                                            41
The Wireless Revolution
  Wireless Computer Network and Access
      Bluetooth (802.15)
            Links up to 8 devices in 10-m area using low-power, radio-based
            Useful for personal networking (PANs)
            FedEx drivers, handheld → computers → cellular
            No docking of handheld units in transmitters, saves 20 million $ year

      Wi-Fi (802.11)
            Set of standards: 802.11a, 802.11b, 802.11g, 802.11n
            Used for wireless LAN and wireless Internet access
            Also known as Wi-Fi → Wireless for Fidelity
            Use access points → Device with radio receiver/transmitter for
            connecting wireless devices to a wired LAN
            Hotspots → One or more access points in public place to provide
            maximum wireless coverage for a specific area
            Weak security features, Susceptibility to Interference (n, MIMO)
COMP 5131                                                                       42
The Wireless Revolution
  An 802.11 Wireless LAN
      Radio waves to transmit network signals from the wired network to
      the client adapters

COMP 5131                                                            43
The Wireless Revolution
  Wireless Computer Network and Access
      WiMax (802.16)
            Wi-Fi range < 300 feet from base stations
            WiMax → Worldwide Interoperability for Microwave Access
            802.16 → 75 Mbps, Robust Security & QOS
            Links Wireless access range of 31 miles
            Require WiMax (Rooftop) antennas

      Broadband Cellular Wireless
            Many cell services offer Wi-Fi capabilities for Internet access
            No Wi-Fi hotspot?, Small card (Laptop) → 3G, 300-500 Kbps

COMP 5131                                                                     44
The Wireless Revolution
  Wireless Sensor Networks
      Networks of hundreds or thousands of interconnected
      wireless devices embedded into physical environment
      to provide measurements of many points over large
      Used to monitor building security, detect hazardous
      substances in air, monitor environmental changes,
      traffic, or military activity
      Devices have built-in processing, storage, and radio
      frequency sensors and antennas
      Require low-power, long-lasting batteries and ability to
      endure in the field without maintenance

COMP 5131                                                    45
The Wireless Revolution
   Wireless Sensor Networks

  The small circles represent lower-level nodes and the larger circles represent high-end nodes. Lower-level nodes forward data to each other
  or to higher-level nodes, which transmit data more rapidly and speed up network performance.

COMP 5131                                                                                                                                       46

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