INFORMATION TECHNOLOGY

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INFORMATION TECHNOLOGY

• Networks and Telecommunications

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Learning Outcomes

• Summarize the individual components of a computer
  network
• Describe the three main network topologies
• Explain the difference between the three main
  forms of network access methods
• Summarize the difference between guided media and
  unguided media
• Explain how a network operating system works
• List the transmitting and receiving devices used
  in a computer network
• Describe the function of TCP/IP
• Summarize the use of a VPN

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Introduction

• introduces the concept of computer networks
• Computer network (or network) - a group of two or
  more computer systems linked together using wires
  or radio waves over a geographical area
• Computer networks that do not use physical wires
  are called wireless
• takes a detailed look at the key conceptsthat
  are integrating computer networks and data
  communications

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The Need for Networking

• A network provides two principle benefits
• The ability to communicate
• The ability to share
• Groupware - software that supports team
  interactions and dynamics including calendaring,
  scheduling, and videoconferencing

is the most popular form of network
communication
E-Mail
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The Benefits of Computer Networking

• Store virtually any kind of information at, and
  retrieve it from, a central location on the
  network
• Combines the power and capabilities of diverse
  equipment providing a collaborative medium to
  combine the skills of different people,
  regardless of physical location
• Enables people to share information and ideas
  easily
• They can work more efficiently and productively

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Networking Basics

• Networks are assembled according to certain
  rules
• Each cabling strand can only support a certain
  amount of network traffic, etc
• Topology - the actual physical organization of
  the computer devices including connections
• Bandwidth - indicates how much information can be
  carried in a given time period over a wired or
  wireless communications link

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Networking Basics (continued)

• The network industry refers to nearly every type
  of network as an area network
• Local Area Network (LAN) - connects network
  devices over a relatively short distance
• Sometimes one building will contain a few small
  LANs, and occasionally a LAN will span a group of
  nearby buildings
• Wide Area Network (WAN) - is a geographically
  dispersed telecommunications network
• Metropolitan Area Network (MAN) - interconnects
  users in a geographic area or region larger than
  a local area network, but smaller than a wide
  area network
• Example A university may have a MAN that joins
  together many of their local area networks
  situated around its campus

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Networks The Big Picture

• A network is made up of many physical elements
• Computers, printers, and other devices
• The manner in which all these items are connected
  is referred to as the network topology
• Network topologies are further subdivided into
  two categories
• Physical topologies
• Logical topologies

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Physical Topologies

• the actual physical organization of the
  computers on the network and its connections
• Bus topology - all devices are connected to a
  central cable
• Star topology - all devices are connected to a
  hub
• Ring topology - all devices are connected to one
  another in a closed loop
• Tree topology - combines the characteristics of
  the bus and star topologies
• Wireless topology - all devices are connected by
  a receiver/transmitter to a special network
  interface card that transmits signals between a
  computer and a server all within an acceptable
  transmission range

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Physical Topologies
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Network Access Methods (Protocols)

• Protocol - the predefined way that someone (who
  wants to use a service) talks with or utilizes
  that service
• The most popular LAN protocols include
• Token Ring
• Ethernet
• Fiber Distributed Data Interface (FDDI)

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Token Ring

• Token ring network - a LAN in which all computers
  are connected in a ring or star topology and a
  token-passing schema is used in order to prevent
  the collision of data between two computers that
  want to send messages at the same time
• Second most widely used protocol on local area
  networks
• Data transfer rates of either 4 or 16 megabits
  per second

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Ethernet

• Ethernet is the most widely installed LAN access
  method originally developed by Xerox
• When it first began to be widely deployed in the
  1980s, Ethernet supported a maximum data rate of
  10 megabits per second (Mbps)
• Fast Ethernet standards have extended traditional
  Ethernet technology to 100 Mbps peak
• Gigabit Ethernet technology extends performance
  up to 1000 Mbps

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Ethernet and Token Ring Network
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Fiber Distributed Data Interface (FDDI)

• FDDI - a set of protocols for sending digital
  data over fiber optic cable
• FDDI networks are token-passing networks that
  supports data rates of up to 100 megabits per
  second
• FDDI networks are typically used as backbones for
  wide area networks

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Fiber Distributed Data Interface
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Networking Hardware

• To be sent from one location to another, a signal
  must travel along a physical path
• The physical path that is used to carry a signal
  between a signal transmitter and a signal
  receiver is called the transmission medium
• Network transmission media - the various types of
  media used to carry the signal between computers
• Two types of transmission media Guided and
  Unguided

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Guided media

• Transmissions material manufactured so that
  signals will be confined to a narrow path and
  will behave predictably
• Three common types of guided media are
  twisted-pair wiring, coaxial cable, and fiber
  optic cable

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Twisted-Pair Wiring

• a type of cable composed of four (or more)
  copper wires twisted around each other within a
  plastic sheath
• The wires are twisted to reduce outside
  electrical interference
• The RJ-45 connectors on twisted-pair cables
  resemble large telephone jacks

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Coaxial Cable

• cable that can carry a wide range of frequencies
  with low signal loss
• Consists of a metallic shield with a single wire
  placed along the center of a shield and isolated
  from the shield by an insulator
• Two different types
• Thinnet coaxial cable - similar to the cable used
  by cable television companies
• Thicknet coaxial cable - similar to thinnet
  except that it is larger in diameter

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Fiber Optic Cable

• Fiber optic (or "optical fiber") - the technology
  associated with the transmission of information
  as light impulses along a glass or plastic wire
  or fiber
• Optical fiber cable can transmit data over long
  distances with little loss in data integrity
• Optical fiber is not subject to interference

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Cable Summary
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Unguided Media

• Unguided media - natural parts of the Earths
  environment that can be used as physical paths to
  carry electrical signals
• Examples include microwaves, infrared light
  waves, and radio waves

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Transmitting and Receiving Devices

• Network adapters
• Modems
• Repeaters
• Wiring concentrators, hubs, and switches
• Bridges, routers, and gateways

• Microwave transmitters
• Infrared and laser transmitters
• Cellular transmitters
• Wireless LAN transmitters

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Network Adapters

• Network adapter - the hardware installed in
  computers that enables them to communicate on a
  network
• The most common form is designed to be installed
  directly into a standard expansion slot inside a
  PC

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Modems

• Modems - provide the means to transmit digital
  computer data typically over ordinary telephone
  lines
• The transmitting modem converts the encoded data
  signal to an audible signal and transmits it
• A modem connected at the other end of the line
  receives the audible signal and converts it back
  into a digital signal for the receiving computer
• Modems are commonly used for inexpensive
  communications between a network and
  geographically isolated computers

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Repeaters

• used to increase the distance over which a
  network signal can be propagated
• A signal travels through a transmission medium,
  it encounters resistance and gradually becomes
  weak and distorted
• The repeater receives the network signal and
  retransmits it at the original transmission
  strength

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Concentrators, Hubs, and Switches

• Concentrators, hubs, and switches - provide a
  common physical connection point for computing
  devices
• Most hubs and all wiring concentrators and
  switches have built-in signal repeating
  capability to perform signal repair and
  retransmission

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Bridges, Routers, and Gateways

• used to interconnect network segments
• Bridges
• Routers
• Bridges and routers - generally used to connect
  networks that use similar protocols
• Gateways
• used to connect networks that use dissimilar
  protocols examples includes TCP/IP and IPX

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Microwave Transmitters Receivers

• commonly used to transmit network signals over
  great distances

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Infrared and Laser Transmitters

• Infrared and laser transmitters - similar to
  microwave systems they use the atmosphere and
  outer space as transmission media
• They require a line-of-sight transmission path
• Useful for signaling across short distances where
  it is impractical to lay cable

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Cellular Transmitters

• Cellular transmitters - radio transmissions and
  therefore have the advantage of being able to
  penetrate solid objects
• A cellular base station at the center of each
  cell contains
• Low-power transmitters
• Receivers
• Antennas
• Common control computer equipment
• Cellular devices are configured to operate at low
  power to avoid interfering with other cellular
  devices in the area

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Wireless LAN Transmitters

• function like hubs and switches in a wired
  environment, only they propagate signals through
  radio waves or infrared light instead of wires

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The Network Operating System

• an operating system that includes special
  functions for connecting computers and devices
  into a local area network
• Two categories
• Client-server
• Peer-to-peer

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Client-Server Networks

• a versatile, message-based, and modular
  infrastructure that is intended to improve
  usability, flexibility, interoperability, and
  scalability as compared to centralized, mainframe
  computing

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Thin Client-Server Networks

• Thin clients - similar to terminals connected to
  mainframes, the server performs the bulk of the
  processing, and the client presents the interface
• Thin clients are usually devoid of floppy drives,
  expansion slots, and hard disks consequently,
  the box or central processing unit is much
  smaller than that of a conventional PC

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Peer-to-Peer Networks

• Enable networked computers to function as both
  servers and workstations

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Internet Technology

• The worlds largest computer network
• Two most influential technologies
• Transmission Control Protocol/Internet Protocol
  (TCP/IP) suite
• World Wide Web (WWW)

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TCP/IP

• TCP/IP - a group, or suite, of networking
  protocols used to connect computers on the
  Internet
• Two main protocols in the suite are
• TCP provides transport functions, ensuring, among
  other things, that the amount of data received is
  the same as the amount transmitted
• The IP part of TCP/IP provides the addressing and
  routing mechanism

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The TCP/IP suite of applications

• File Transfer Protocol (FTP) - allows files to be
  downloaded off or uploaded onto a network
• Simple Mail Transfer Protocol (SMTP) - TCP/IPs
  own messaging system for e-mail
• Telnet protocol - provides terminal emulation
• Hypertext Transfer Protocol (HTTP) - allows Web
  browsers and servers to send and receive Web
  pages
• Simple Network Management Protocol (SNTP) -
  allows the management of networked nodes to be
  managed from a single point

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The TCP/IP Protocol Suite
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World Wide Web

• The World Wide Web is a client-server environment
• Information is managed through Web sites on
  computers called Web servers
• Accessing Web sites is done through the use of
  client software (i.e., a browser) and the
  Internets HTTP
• Computers and Web sites on the Internet are
  linked through documents called Web pages written
  in HTML

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Intranet vs. Extranet

• Intranet an internalized portion of the
  Internet, protected from outside access, that
  allows an organization to provide access to
  information and application software to only its
  employees
• Extranet - a private network that uses the
  Internet protocol and the public
  telecommunication system to securely share part
  of a business's information or operations with
  suppliers, vendors, partners, customers, or other
  businesses

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Virtual Private Network (VPN)

• VPN - a private WAN that uses the Internet as a
  low-cost WAN backbone to transport data between
  two or more geographically separate sites
• Advantages that a VPN has over a dedicated-line
  WAN
• The cost of implementation
• No need to lay cable or lease dedicated lines
  between the remote sites needing to connect
• Businesses can network remote offices into one
  large WAN and provide access to the Internet

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Intranet, Extranet, and VPN Technologies