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COE 342 - 1 Data and Computer Communications

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Title: COE 342 - 1 Data and Computer Communications


1
COE 342 - 1 Data and Computer Communications
  • Data Communications Networking Overview

2
Communication Model
3
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

4
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

5
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.

6
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

7
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.

8
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

9
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

10
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

11
Simplified Data Communication Model
12
Direct point to point connection
13
Direct point to point connection
14
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.

15
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

16
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.

17
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.

18
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.

19
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

20
Network technology
  • Circuit switching
  • Packet switching
  • Frame relay
  • Asynchronous Transfer Mode (ATM)

21
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.

22
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.

23
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.

24
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

25
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.

26
NetworkingConfiguration
  • Subscriber connection
  • Telephone network
  • DSL
  • Cable TV
  • Satellite
  • SONet Synchronous Optical Network, a standard
    for connecting fiber-optic transmission systems.
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