TELECOMMUNICATIONS

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• TELECOMMUNICATIONS
• and
• NETWORKS

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All Organizations Need to Share and Communicate
Information...

• Externally with other organizations
• Internally among employees.

- the electronic movement of information over
public or private networks - a communications,
data exchange, and resource-sharing system
created by
, or protocols, so that they can
work together.
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Benefits of a NETWORK

• 1. The ability with other people (
  is the most of
  network communications)
• 2. The ability to share
• I
• Software
• Peripheral devices
• P

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Ways different types of networks are
differentiated

• Size and Proximity of the network
• LAN versus WAN
• Architecture
• Peer-to-Peer versus Client/Server
• Protocols Used
• Ethernet for LAN
• Transmission Control Protocol/Internet Protocol
  (TCP/IP)
• Topology
• Bus, Star, Ring, Hybrid, Wireless
• Media
• Coaxial, Twisted-pair, Fiber-optic, Wireless media

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Network Proximity

• L Network--Connects computers in
  relatively
• W Networks-- Connects computers
  that may be dispersedamong a number of
  buildings, or even in different cities.
• Internet--International Network of Networks.

WAN
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Types of LANs

• P
• Each user can share their computers resources
  with other LAN users

C Only resources on specific computers called
serverscan be shared
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Peer-to-Peer Networks

• Peer-to-peer (P2P) network - any network and in
  which computers in the network to
  the public files located on all other workstations

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Peer-to-Peer LAN Advantages

• Control is distributed to the LAN users
• Users who own data have control over who accesses
  it
• Inexpensive and easy to install
• You just need
• A
• A network operating system on both computers,
  (any version of since 95).
• Network
• Network resources are distributed
• A disaster on one users computer doesnt
  destroy all the data on the network

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Peer-to-Peer LAN Disadvantages

• Control is distributed to the LAN users
• No one person or group can know what resources
  are available.
• No one person or group is
• Performance is poor
• Since the computers share resources and some
  computers can even access the hard drives of
  other computers, the result is that
• The performance of a PC also slows down when
  someone on the network accesses it.
• As a result, peer-to-peer networks are

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Client/Server Networks

• Client - a computer that is designed to
  from a server
• Server - a computer that is dedicated to
  providing information in response to external
  requests
• Client/server network - model for applications in
  which the
  takes place on a , while the
  
  is handled by the

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The Client/Server Model
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Client/Server Model A Business View

• The different Client/server implementations
  differ according to
• Where the processing for the
• Where the processing of occurs
• Where the (DBMS) and are located

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Flexible Applications
Server
Client
Business Logic
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Any Combination is Possible
Client
Data Management
Business Logic
Design Server
Presentation
Data Management
Business Logic
Production Server
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Client/Server Advantages

• Application can be structured to match
  organizational requirements since it is both
• Can change the implementation of this model as
  the organization changes in size since the
  Client/Server model provides the to
  whatever is
• Data access is regardless of where the data is
  stored.
• Separate programs are more easily maintained and
  can be reused.
• One for all of the and easier to

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Client/Server LAN Disadvantages

• All shared resources reside on computers call
  servers
• If a disaster occurs on the server all the data
  is in jeopardy
• If the server malfunctions,
• Expensive
• Usually require expensive hardware and extra
  staff to manage
• Only of client/server costs are tied
  up in
• The remaining is in the form of
  - both IT professionals and knowledge
  workers.

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Client/Server Networks

• Network operating system (NOS) - the operating
  system that runs a network, steering information
  between computers and managing security and users
  
• Major client/server NOSs are Windows NT, Windows
  2000, Novell NetWare, Linux, and Unix
• P - occurs when the sending computer divides a
  message into a number of efficiently sized units
  called packets, each of which contains the
  address of the destination computer
• Router
• Used to
• Can also sit (serving as a ).
• An intelligent connecting device that examines
  each packet of data it receives and then decides
  which way to send it onward toward its destination

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Network Data Transfer Process

• Network operating system on the source machine
  to be sent into segments of predetermined length
  called
• Network operating system on the source uses a
  communications protocol to
• Network Operating System on the source sends
  packets over the network.
• Packets are routed as necessary through the
  network depending on the transmission mediums,
  transmission signal characteristics and access
  control methods.
• Network Operating system on the destination
  receives packets over the network.
• Network Operating system on the destination
  by looking at the communication protocol
  information. Requests retransmission of any
  missing data.

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Connecting Networks
The connection between a LAN and a larger
network is usually accomplished using a device
called a
WAN or Backbone
LAN
Router
LAN
Routers are responsible for
that messages take from
the sending computer to the destination computer.
Router
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WANs
Once a network is linked to a , it becomes part
of the Internet community.
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Wide Area Network
Packet Switched Network Data is packaged in
for transmission.
Each packet follows through the network.
R
R
R
R
R
R
R
R
R
R
R
R
R
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PROTOCOLS

• Protocol - a that specifies the as well as
  the during transmission
• Following a certain , allows for
  interoperability
• Interoperability - the capability of two or more
  computer systems to share data and resources,
  even though they are made by different
  manufacturers
• Two primary communications protocols are TCP/IP
  and Ethernet
• TCP/IP is used for
• Ethernet is used by computers in a to
  communicate

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Ethernet

• Ethernet - a physical and data layer technology
  for LAN networking

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Ethernet

• Defines the standards used in a LAN.
• Used to describe the
• W (Co-axial, twisted-pair, fiber-optic)
• How bits are physically transmitted using those
  media
• Access control rules
• Data transmission speeds
• Details and works on the principle of
  and
• Helps insure the compatibility of different
  devices so that many people can attach to a
  common cable.

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Transmission Control Protocol/ Internet Protocol

• Transmission Control Protocol/Internet Protocol
  (TCP/IP) - provides the technical
  as well as for large numbers of private
  network
• The TCP/IP protocol suite is made up of over
  protocols.
• The two are TCP and IP
• TCP provides for
• IP provides the mechanism

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TRANSMISSION CONTROL PROTOCOL / INTERNET PROTOCOL
(TCP / IP)

• Allows computers to
  regardless of their
  or hardware.
• Transmission Control Protocol
• Breaks information into data packets
• Reassembles packets when received
• Checks for lost packets
• Internet Protocol
• Each computer given a unique IP address
• Used to
• 209.1.144.212

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TCP/IPs four-layer reference model

• The layer allows users and
  applications to access
• F protocol (FTP)
• Simple protocol (SMTP)
• T provides terminal emulation that
  allows a terminal with to be
  able to connect to a host computer (which will
  control everything).
• H protocol (HTTP)
• Simple network management Protocol (SNMP)

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TCP/IPs four-layer reference model

• The layer handles
• The layer handles the packets
  ( , etc.)
• The layer
  details how is
  through the networking

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How Does the Internet Work??
http//www.howstuffworks.com/web-server.htm
1 2 Browser communicates with
to get
209.1.144.212
3 Browser connects to specific server, uses GET
request to ask for file you wish to see. 4
Server sends HTML text to your browser. HTML
tags are read and page displayed.
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Network Topology

• The of computers in a network.

• Bus
• Ring
• Star
• Mesh
• Hybrid
• Wireless

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Bus Topology

• All computers are connected /cable.
• One device transmits a communications signal,
  which is broadcast to the entire network
• Most LAN topology. Relatively

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Ring Topology

• All devices connected to one channel in the
  form of a closed loop (ring). Each device is
  connected directly to two other devices.
• All messages in one direction.
• Relatively and
  , but they offer high bandwidth and can
  span large distances.
• Used primarily in
  that use token ring software.

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Star Topology

• All devices are , called a hub. The
  hub . All network traffic
  the hub.
• Relatively easy to install and manage.
• B can occur because of the
  must through the , and if
  the hub goes down, the entire network is down.

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Hybrid Topology

• Groups of star-configured workstations that are
  connected to a liner bus cable, combining
  characteristics of bus and star topologies.
• Often

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Wireless Topology

• Computers are connected by to a
  wireless access point (which is directly
  connected to a wired LAN)
• Must be within a certain number of feet from the
  access point to communicate wirelessly
  (depending on the technology being used)

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Network Transmission Media

• Refers to the various types of media used to
• Wire media (guided)
• Transmission material manufactured so that
  signals will be and will behave .
• Three most commonly used types include
• Twisted-pair wiring
• Coaxial cable
• Fiber optic (or optical fiber)
• Wireless media (unguided)

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Network Communications Media
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Network Communications Media

• C cable - a better-constructed version of the
  phone twisted-pair cable.

Twisted Pair Wire
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Network Communications Media

• Wireless communications (radio waves, microwaves,
  infrared) media radiate information into the air,
  either very narrowly beamed or in many directions
  like ripples from a pebble tossed into a pond.

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Business Networks

• You can build your own wired network or you can
  from a national provider.
• Virtual private network (VPN) - a way to use the
  telecommunication infrastructure
  (e.g., ) to provide secure access to an
  organizations network
• T software is used to create a connection
  between two different servers ( ).
• Data packets are

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Telecommunications Methods

• Data are generally expressed in thousands or
  millions of bits per second (kbps/mbps)
• Phone Lines use a but very .
  Handles only analog signals. 28.8-56 kbps
• D ( ) regular divided into voice
  (analog) and information (digital channels).
  Always-on connection. Can make phone calls while
  online.
• C Operates over Provides
  a constant connection to the Internet, although
  its speed depends on how many users (such as your
  neighbors) are online.

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Researchers explore scrapping and rebuilding the
Internet

• In order to address the problems that were not
  envisioned when the Internet was initially
  created, some are suggesting rebuilding the
  Internet using a approach.
• S
• The Internet was designed to be open and flexible
  and all users were assumed to be trustworthy.
  Internet protocols were not designed to
  authenticate users and their data. Firewalls and
  spam filters are now being used to control
  security.
• Solution data not passed along until

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• Mobility
• Initially, computers were fixed in location so IP
  addresses were assigned to devices in a fixed
  location. Wireless mobile computing is
  presenting challenges related to data flow.
• Solution R so that addresses are based on the
  device, rather than the location.
• Ubiquity (called in our class notes)
• When the Internet was first designed, there were
  relatively few computers connected to it. The
  addressing system has become strained due to the
  proliferation of personal computers and mobile
  devices.
• Solution assign and have those same
  devices connected to an addressed gateway, which
  is then connected to routers and the rest of the
  Internet
• Result is fewer devices to keep track of and
  improved efficiency.
• These changes may happen over the next 10-15
  years. They (expected to cost as
  computer hardware and software and Internet
  infrastructure are replaced)

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The End

• The slides that follow this slide contain
  additional details related to the material found
  in some of your earlier slides. It is HIGHLY
  RECOMMENDED THAT YOU STUDY THESE ADDITIONAL
  SLIDES because they reinforce other concepts that
  you have already seen (and that you might see on
  an upcoming exam)

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Network Communications

• Network Card--Allows a PC to communicate with
  the network.
• Digital Signal--Discrete signal, series of ons
  and offs. Computer thinks in terms of zeros
  (off)and ones (on). Very abrupt.
• Analog Signal--Continuous wave-like
  communication. Readings can fall within a range
  temperature, humidity, air pressure, radio
  signals, phone signals, TV signals, electricity.

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• Dont we have a problem??
• Humans and their devices think in terms of
  analog continuous waves.
• Computers think in terms of digital signals
  abrupt stops and starts.
• MODEM Modulator/Demodulator
• converts the digital signals of your computer
  into an analog form that can be transmitted over
  a telephone line and then converts the analog
  signal back to digital signals at the other end
  of the transmission.

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Modems
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Telecommunications Methods
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Network Communications Media

• Twisted Pair Wire
• Coaxial Cable
• Fiber Optical Cable (Optical Fiber)
• Infrared
• Microwave
• Cellulartransmissions

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Twisted Pair Wire

• Two or more strands of copper wire twisted
  together, covered by insulation.
• Used for direct connections over short distances
  in LANs
• Type of Signal Carries an electrical signal
• Other Characteristics Cheap, but slow. Not used
  very frequently anymore. Does not protect well
  against electrical interference
• Other Uses Telephone lines inside your home

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Coaxial Cable

• Used for direct connections over short
  distances in LANs but over a slightly larger
  distance than twisted pair.
• Type of Signal Carries an electrical signal
• Other Characteristics Better signal quality and
  more capabilities than twisted pair. More
  reliable.
• Other Uses Cable TV

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Optical Fiber / Fiber Optics

• Used for longer distance connections in WANs that
  will carry large amounts of data.
• Type of Signal Glass fibers transmit information
  as pulses of light.
• Other Characteristics Faster and more expensive
  than TP or Coax.
• Other Uses High speed, cross country telephone
  lines. Also being installed in cities as an
  infrastructure for a wide variety of
  communications uses.

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Fiber-Optic Cable

• Fiber-optic Cable
• Many extremely thin strands of glass or plastic
  bound together in a sheathing which transmits
  signals with light beams. Can be used for voice,
  data, and video.

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Infrared

• Used for Wireless, short range LAN connections
• Type of Signal Infrared beam of light. Requires
  line of sight communication. Uses a red light
  that you cant see to transmit info.
• Other Characteristics Advantage is lack of wires
  connecting devices, portability.
• Other Uses many types of remote controls,
  wireless keyboards and mice.

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Microwave

• Used for long range WAN connections.
• Other Characteristics Require line-of-sight
  connection. Signal can be boosted through the
  use of repeater devices located between
  transmitter and receiver.
• Other UsesUsed by satellites, cable
  companies, cellular phones, broadcast radio.

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The Internet

• First developed by the US Department of Defense
  in 1969. Over time, international connections
  were made, and the Internet really took off
  during the early 1990s when the technology behind
  web pages was developed and corporate users were
  given access to it, and the Internet has evolved
  into its present form.
• The Internet and the World Wide Web are not the
  same thing. There are many different resources
  and services on the Internet, and the World Wide
  Web is just one of the resources found on the
  Internet.
• Initial Internet communications were text-only,
  but now Internet communications can also be in
  the form of audio, video, and graphics
• Two types of computers on the Internet
• Clients
• Servers
• Web Servers FTP Servers (used to upload and
  download files
• Mail Servers Internet Relay Chat (IRC) Servers

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Connecting to the Internet

• Dial up (dial in) using the telephone lines and a
  modem.
• Constant Connections
• Wired (LAN) Local Area Network network card
  required
• Cable modems and DSL (Digital Subscriber Line)
• Wireless Network (wireless LAN)
• PCs and laptop computers could access the
  Internet without relying on physical
  wiring. Wireless Access Point/Base Station
  Required
• Use wireless phones to retrieve email, access the
  Internet, or a corporate database.
• Many of the buildings on campus are in wireless
  zones.

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World Wide Web

• Hypertext Markup Language (HTML)
• Hypertext is used to connect or link documents
  together hyperlinks.
• Web browsers are the software capable of
  understanding HTML files and HTML coding.
• Internet Explorer approximately 89 market
  share
• Safari found on Macs faster than IE, can read
  web pages aloud
• The Netscape Family of Browsers
• Netscape dominant in webs early days, before IE
• Mozilla 2 market share
• FireFox 7 market share more stable and
  secure than IE, can be found on computers running
  Windows, Linux or the Macintosh operating system.