Introductory Lecture-Data Communication and Computer Networks-Lecture Slides, Slides of Data Communication Systems and Computer Networks

These are a set of Lecture Slides on the subject of Data Communication and Computer Networks at Univeristy of Delhi by Dr. Sonam Zinta. It includes: Data, Communications, Computer, Networks, Protocols, Standards, Models, Accuracy, Jitter, Transmission

Typology: Slides

2011/2012

Uploaded on 07/05/2012

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EEE314
Data Communications and
Computer Networks
Lecture # 1
Introduction
7.2.2011
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EEE

Data Communications and

Computer Networks

Lecture # 1

Introduction

7.2.

Course Objectives

In this course four major concepts will be discussed namely

  • Data communications
  • Networking
  • Protocols and standards
  • Networking models

Data Communications

  • Communication is sharing of information
  • Telecommunication is communication taking place over distance
  • Data communications are the exchange of data between two devices via some form of transmission medium such as a wire cable. - The word data refers to information presented in whatever form is agreed upon by the parties creating and using the data.

Fundamental characteristics of Data

Communications

  • Delivery: The system must deliver data to the correct destination
  • Accuracy: The system must deliver the data accurately (unaltered, unchanged).
  • Timeliness: The system must deliver data in a timely manner (without delay, synchronously).
  • Jitter: Jitter refers to the variation in the packet arrival time(without uneven delay).

Data representation

Information today comes in forms

  • Text
  • Numbers
  • Images
  • Audio
  • Video

Data Flow

(a) Simplex

(b) Half Duplex

(c) Full Duplex

Physical structures of network

  • Dedicated link between two devices
  • More then two devices sharing the link

Network physical Topologies

  • The term physical topology refers to the way in which a network is laid out physically
  • There are four basic topologies
    • Mesh
    • Star
    • Bus
    • Ring

Star topology

  • Each device has a dedicated point-to-point link only to a central controller, usually called a hub or a switch.
  • Advantages
    • No direct traffic between devices
    • Less expensive than mesh topology
    • Each device needs only one link and one I/O port
    • Easy to install and reconfigure
    • Far less cabling required
    • Easy fault isolation
  • One big disadvantage of a star topology is the dependency of the whole topology on one single point, the hub. If the hub goes down, the whole system is dead.

Bus topology

  • A multipoint topology in which Nodes are connected to the bus cable by drop lines
  • The principal advantage of this topology are
    • Cost.
    • no hubs are required.
    • shorter lengths of cable can be used.
    • It is also easy to expand.
  • Disadvantages include
    • Difficult reconnection and fault isolation.
    • Difficult to add new devices.
    • Signal reflection at the taps can cause degradation in quality.

Hybrid Topology

  • A network can be hybrid. For example, we can have a main star topology with each branch connecting several stations in a bus topology

Network Models

  • Computer networks are created by different entities.
  • Standards are needed so that these heterogeneous networks can communicate with one another.
  • The two best-known standards are the OSI model and the Internet model.

Local Area Network (LAN)

  • LAN is usually privately owned and links the devices in a single office, building, or campus.
  • LANs are designed to allow resources to be shared between personal computers or workstations.
  • In addition to size, LANs are distinguished from other types of networks by their transmission media and topology.
  • In general, a given LAN will use only one type of transmission medium. The most common LAN topologies are bus, ring, and star.

Wide Area Network

  • A wide area network (WAN) provides long-distance transmission of data, image, audio, and video information over large geographic areas that may comprise a country, a continent, or even the whole world.
  • The switched WAN connects the end systems, which usually comprise a router that connects to another LAN or WAN.
  • A WAN can be
    • As complex as the backbones that connect the Internet or
    • As simple as a dial-up line that connects a home computer to the Internet.
  • An early example of a switched WAN is X.25, a network designed to provide connectivity between end users.
  • A good example of a switched WAN is the asynchronous transfer mode (ATM) network, which is a network with fixed-size data unit packets called cells.