COE 342 - 1 Data and Computer Communications

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COE 342 - 1 Data and Computer Communications

• Data Communications Networking Overview

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Communication Model
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Communication Model

• Fundamental purpose of communications system is
  exchange of data between two parties
• The key elements of a communication model are
• Source Generates data to be transmitted
• Transmitter Converts data into transmittable
  signals (modulation, encoding, )
• Transmission System Carries data
• Receiver Converts received signal into data (the
  opposite of the Transmitter role)
• Destination Takes incoming data

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Communications Tasks

• Transmission system utilization
• Interfacing
• Signal generation
• Synchronization
• Exchange management
• Error detection and correction
• Flow control
• Addressing
• Routing
• Recovery
• Message formatting
• Security
• Network management

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Communications Tasks

• Transmission system utilization
• Making efficient use of transmission facilities
• Multiplexing is used to allocate the total
  transmission medium among number of users
• Congestion control is needed to assure that the
  transmission system is not overwhelmed
• Interfacing Interfacing here refers to how to
  interface communicating devices to the
  transmission system
• Signal generation Most forms of computer
  communication depend on the use of
  electromagnetic signals propagated over
  transmission media. Thus, we need to generate
  signals from the data to be transmitted.

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Communications Tasks

• Synchronization The receiver needs to know when
  the signal start and ends. Also, it needs to know
  the duration of each signal
• Exchange management The communicating parties
  need to agree on a variety of requirements to
  communicate usefully. Such conventions include
• Signal timing
• How to start/end conversation
• Simultaneous transmission or taking turns
• Amount of data to be sent at one time
• Data format
• Dealing with errors

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Communications Tasks

• Error detection and correction
• In all communication system there is a potential
  for error (signal distortion, attenuation,
  interference)
• In most cases, error in transmission is not
  accepted (tolerated)
• We need to have a technique to detect errors in
  transmission and even better to have a technique
  to correct errors
• Flow control Flow control is required to assure
  that the source does not send information too
  fast
• Addressing When more than two devices share
  transmission facility
• Each system need to have unique address.
• Source need to identify the destination by its
  address.

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Communications Tasks

• Routing the transmission system must assure that
  the destination system receive the data
• Recovery Recovery is needed when the information
  exchange is interrupted or to restore the system
  to the point prior to the beginning of the
  exchange
• Message formatting Communicating parties need to
  agree on the form of data to be transmitted such
  as the binary code for characters
• Security
• Data sender need to assure that only the intended
  destination receive the data.
• Destination need to be sure that what he recived
  was sent actually by the purported sender.
• Destination need to be sure that the data has not
  been altered

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Communications Tasks

• Network management Network management is needed
  to
• configure the system
• Monitor the system status
• React to failures and overload
• Plan for future growth

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Data Communication

• Sending an email (simplified)
• User A wrote an email message and he wants to
  send it to B
• When the user click send, the email program will
  prepare binary message that has the digital
  equivalent of email body, B address and some
  control bit streams.
• The computer will send the bit stream as a
  digital signal to the transmitter (modem for
  example)
• Transmitter will convert the digital signal to a
  signal suitable for the transmission system
  (analog signal for example)
• Transmission system will carry the signal to the
  destination recover.
• The receiver convert the received signal to a
  binary signal and send it to the computer
• Destination computer will take the received
  signal convert it to binary data and store it in
  the memory
• Email program will read the binary data removes
  added

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Simplified Data Communication Model
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Direct point to point connection
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Direct point to point connection
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Computer network

• Computer network is a group of computer systems
  linked together.
• Computer networks can be classified in different
  ways. Follows is a classification that depends
  on the geographical position of the computers
• WAN wide-area network The computers are farther
  apart and are connected by telephone lines or
  radio waves.
• MAN metropolitan-area network A data network
  designed for a town or city.
• CAN campus-area network The computers are
  within a limited geographic area, such as a
  campus or military base.
• LAN local-area network The computers are
  geographically close together (in the same
  building).
• HAN home-area network A network contained
  within a user's home that connects a person's
  digital devices.

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Local-area network

• A computer network that spans a relatively small
  area.
• Most LANs are confined to a single building or
  group of buildings.
• A LAN can be connected to other LANs over any
  distance via telephone lines or radio waves. A
  system of LANs connected in this way is called a
  wide-area network (WAN).
• Most LANs connect workstations and personal
  computers.
• Each node (individual computer ) in a LAN has its
  own CPU with which it executes programs, but it
  also is able to access data and devices anywhere
  on the LAN.
• Users can share devices, such as printers, as
  well as data.
• Users can also use the LAN to communicate with
  each other, by sending e-mail or engaging in chat
  sessions.
• There are many different types of LANs examples
• Ethernets being the most common for PCs.
• AppleTalk is most common for Apple Macintosh
  networks

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Ethernet

• A local-area network (LAN) architecture developed
  by Xerox Corporation in cooperation with DEC and
  Intel in 1976.
• Ethernet uses a bus or star topology
• Ethernet data transfer rates
• Ethernet 10 Mbps.
• Fast Ethernet 100 Mbps.
• Gigabit Ethernet 1 gigabit (1,000 megabits) per
  second
• The Ethernet specification served as the basis
  for the IEEE 802.3 standard
• It is one of the most widely implemented LAN
  standards.

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Wide Area Network

• A computer network that spans a relatively large
  geographical area.
• Typically, a WAN consists of two or more
  local-area networks (LANs).
• Computers connected to a wide-area network are
  often connected through public networks, such as
  the telephone system.
• They can also be connected through leased lines
  or satellites.
• The largest WAN in existence is the Internet.

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Metropolitan Area Network

• A data network designed for a town or city.
• In terms of geographic breadth, MANs are larger
  than local-area networks (LANs), but smaller than
  wide-area networks (WANs).
• MANs are usually characterized by very high-speed
  connections using fiber optical cable or other
  digital media.

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Wireless network

• Wireless network is a type of network that uses
  high-frequency radio waves rather than wires to
  communicate between nodes.
• Hybrid wireless network is an emerging networking
  that consists of wireless components that
  communicate with a network that uses cables in a
  mixed-component network.
• Wireless network is now common in
• Business LANs
• WAN (voice data)
• Advantages of using wireless network
• Easy to install and configure.
• Provides mobility

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Network technology

• Circuit switching
• Packet switching
• Frame relay
• Asynchronous Transfer Mode (ATM)

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Circuit switching

• A type of communications in which a dedicated
  channel (or circuit) is established for the
  duration of a transmission.
• The most famous circuit-switching network is the
  telephone system, which links together wire
  segments to create a single unbroken line for
  each telephone call.
• Circuit-switching systems are ideal for
  communications that require data to be
  transmitted in real-time such as live audio and
  video.
• Circuit-switching networks are sometimes called
  connection-oriented networks.

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Packet switching

• Communication method that divides messages into
  packets and sends each packet individually.
• Each packet is then transmitted individually and
  can even follow different routes to its
  destination.
• Once all the packets forming a message arrive at
  the destination, they are recompiled into the
  original message.
• Packet-switching networks are more efficient if
  some amount of delay is acceptable. as e-mail
  messages and Web pages.
• The Internet is based on a packet-switching
  protocol, TCP/IP.
• Most modern Wide Area Network (WAN) protocols,
  including TCP/IP, X.25, and Frame Relay, are
  based on packet-switching technologies.

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Frame relay

• Packet switching systems have large overheads to
  compensate for errors.
• Modern systems are more reliable (dramatically
  lower errors rate)
• Errors can be caught in end system
• Most overhead for error control is stripped out
• Frame relay is a packet-switching protocol that
  uses much lesser overhead for error control.
• Frame Relay networks can support data transfer
  rates up to 2 Mbps (compared to 64Kbps for
  regular packet switching)
• Frame Relay is quite popular in the U.S. because
  it is relatively inexpensive. However, it is
  being replaced by faster technologies, such as
  ATM.

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Asynchronous Transfer Mode (ATM)

• A network technology based on transferring data
  in cells or packets of a fixed size.
• The cell used with ATM is relatively small
  compared to units used with older technologies.
• The small, constant cell size allows ATM
  equipment to transmit video, audio, and computer
  data over the same network, and assure that no
  single type of data hogs the line.
• ATM creates a fixed channel, or route, between
  two points whenever data transfer begins.
• ATM attempts to combine the best of both worlds
  -- the guaranteed delivery of circuit-switched
  networks and the robustness and efficiency of
  packet-switching networks.
• Speed up to Gbps range

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Transmission Control Protocol/Internet Protocol
(TCP/IP)

• A suite of communications protocols used to
  connect hosts on the Internet.
• TCP/IP uses several protocols, the two main ones
  being TCP and IP.
• TCP/IP establishes a connection between two hosts
  so that they can send messages back and forth for
  a period of time.
• TCP is a protocols that enables two hosts to
  establish a connection and exchange streams of
  data.
• TCP establishes a virtual connection between a
  destination and a source.
• TCP guarantees delivery of data and also
  guarantees that packets will be delivered in the
  same order in which they were sent.
• IP specifies the format of packets, also called
  datagrams, and the addressing scheme.
• IP is like the postal system It allows you to
  address a package and drop it in the system, but
  there's no direct link between you and the
  recipient.

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NetworkingConfiguration

• Subscriber connection
• Telephone network
• DSL
• Cable TV
• Satellite

• SONet Synchronous Optical Network, a standard
  for connecting fiber-optic transmission systems.