Data Communication _ Networking An Introduction

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					       Data Communication & Networking:
               An Introduction




Dr. Indranil Sen Gupta   Data Commn. & Networking: Introduction   Slide 1
                             Introduction

• The 1970s and 1980s have seen a merger of
  computer science and data communication.
• Byproducts of the revolution:
      – No fundamental differences between data processing
        equipments (computers) and data communication
        equipments (transmission, switching).
      – No fundamental differences among data, voice, and
        video communication.
      – The dividing lines between uniprocessors,
        multiprocessors, LAN, MAN and WAN have blurred.
Dr. Indranil Sen Gupta   Data Commn. & Networking: Introduction   Slide 2
                     A Communication Model




                  Figure 1.1 from the book by Stallings




Dr. Indranil Sen Gupta   Data Commn. & Networking: Introduction   Slide 3
                   Key Elements of the Model
• Source: generates the data to be transmitted (e.g.
  telephones, PCs).
• Transmitter: transforms and encodes the information in
  such a way as to produce signals that can be transmitted
  across sore sort of transmission system (e.g. MODEM).
• Transmission System: a single transmission line or a
  complex network connecting source and destination.
• Receiver: accepts the signal from the transmission system
  and converts it into a form that can be handled by the
  destination device.
• Destination: takes the incoming data from the receiver.
Dr. Indranil Sen Gupta   Data Commn. & Networking: Introduction   Slide 4
 Some of the key tasks performed by a data
          communication system
• Transmission system                        •   Addressing
  utilization                                •   Routing
• Interfacing                                •   Recovery
• Signal generation                          •   Security
• Synchronization                            •   Network Management
• Error detection and
  correction
• Flow control



Dr. Indranil Sen Gupta   Data Commn. & Networking: Introduction       Slide 5
     Simplified Data Communication Model




                         Figure 1.2 from the book by Stallings




Dr. Indranil Sen Gupta       Data Commn. & Networking: Introduction   Slide 6
                         Networking Concepts

• In its simplest form, data communication takes
  place between two devices that are directly
  connected by some point-to-point transmission
  medium.
• Sometimes they may not be directly connected:
      – The devices are very far apart.
      – Many links may be shared.
• Solution?
      – Attach each device to a communications network.
Dr. Indranil Sen Gupta    Data Commn. & Networking: Introduction   Slide 7
                         Figure 1.3 from the book by Stallings




Dr. Indranil Sen Gupta       Data Commn. & Networking: Introduction   Slide 8
                   Networking Terminologies

• LAN/MAN:
      – Scope is small (same room or building or Campus).
      – Owned by the same organization that owns the attached
        devices.
      – Data rates are typically much higher.
      – LANs usually employ a broadcast network approach.
            • No intermediate switching node
            • Only one station at a time can transmit packets
      – Modern LAN technologies use packet/cell switching
        techniques.
Dr. Indranil Sen Gupta   Data Commn. & Networking: Introduction   Slide 9
                                    Contd.
• WAN:
      – Usually covers a large geographic area.
      – Relies at least in parts on circuits provided by a
        common carrier.
      – Typically consists of a number of switching nodes.
      – Traditional technologies:
            • Circuit switching
            • Packet switching
      – Recent technologies:
            • Frame relay
            • ATM
Dr. Indranil Sen Gupta   Data Commn. & Networking: Introduction   Slide 10
       Protocols and Protocol Architectures

• A protocol is used for communication between
  entities in different systems.
• Instead of a single module for performing
  communications, there is a structured set of
  modules that implement the communication
  functions.
      – Called the Protocol Architecture



Dr. Indranil Sen Gupta   Data Commn. & Networking: Introduction   Slide 11
                TCP/IP Protocol Architecture

• Most widely used inter-operable architecture.
• Consists of a large number of protocols, called
  TCP/IP protocol suite.
• Simplified layer model:
      – Physical: covers the physical interface between a host
        and the transmission medium.
      – Network Access: concerned with access to and routing
        data across a network for two end systems attached to
        the same network.

Dr. Indranil Sen Gupta   Data Commn. & Networking: Introduction   Slide 12
                                    Contd.

      – IP: used to provide routing function across multiple
        networks.
            • This protocol is implemented not only in the end systems but
              also in the routers.
      – TCP: ensures that data is exchanged reliably.
            • Also known as host-to-host layer.




Dr. Indranil Sen Gupta   Data Commn. & Networking: Introduction       Slide 13
                         Figure 1.9 from the book by Stallings




Dr. Indranil Sen Gupta        Data Commn. & Networking: Introduction   Slide 14
                          The OSI Model

• Developed by ISO as a model for a computer
  communication architecture, and as a framework
  for developing protocol standards.
• Although more systematically designed, it
  ultimately lost its battle to TCP/IP, which has
  evolved in an ad-hoc manner.
• Based on a seven layer model.


Dr. Indranil Sen Gupta   Data Commn. & Networking: Introduction   Slide 15
                         Seven Layer Model
• Application: provides access to OSI environment for users.
• Presentation: provides independence to the application processes from
  differences in data representation.
• Session: establishes, manages and terminates connections (sessions)
  between co-operating applications.
• Transport: provides reliable, transparent transfers of data between end
  points; provides end-to-end error recovery and flow control.
• Network: provides upper layers with independence from the data
  transmission and switching technologies used to connect systems.
• Data Link: provides for the reliable transfer of information across the
  physical link.
• Physical: concerned with transmission of raw bit stream over some
  physical medium.
Dr. Indranil Sen Gupta   Data Commn. & Networking: Introduction    Slide 16
                   Figure 1.11 from the book by Stallings




Dr. Indranil Sen Gupta    Data Commn. & Networking: Introduction   Slide 17

				
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