Lec1 :- Data communication and network

DATA COMMUNICATION AND
NETWORKING.
Compile by Dhrumil shah
1

1.2
Chapter 1
Introduction
1. Introduction
2. Fundamental characteristics
3. Components of data communication
4. Data representation
5. Data Flow

SIMPLE DATA COMMUNICATION MODEL
 Simplified block diagram of data communication network

SIMPLE DATA COMMUNICATION MODEL
 Source :Where the data is originated.
 Transmitter : Convert data into suitable form for
transmission through the medium
 Communication System: Medium through which signal
is sent.
 Receiver : Which receives the signal and convert it into
data or message.
 Destination : where the data is sent.
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FUNDAMENTAL CHARACTERISTICS OF DATA
COMMUNICATION
 Delivery : The system must deliver data to the correct destination
 Accuracy : The system must deliver data accurately
 Timeliness : The system should transfer data within time .
 Jitter : It refers to the variation in the packets arrival tome .
1.6

1.8
Figure 1.1 Components of a data communication system

1.10
1-1 DATA COMMUNICATIONS
The term telecommunication means communication at a
distance. The word data refers to information presented in
whatever form is agreed upon by the parties creating and
using the data. Data communications are the exchange of
data between two devices via some form of transmission
medium such as a wire cable.

1.11
Figure 1.2 Data flow (simplex, half-duplex, and full-duplex)

TRANSMISSION MODES
 Simplex
 signals transmitted in one direction
 eg. Television
 Half duplex
 both stations transmit, but only one at a time
 eg. police radio
 Full duplex
 simultaneous transmissions
 eg. telephone

1.14
NETWORKS
A network is a set of devices (often referred to as nodes)
connected by communication links. A node can be a
computer, printer, or any other device capable of sending
and/or receiving data generated by other nodes on the
network. A link can be a cable, air, optical fiber, or any
medium which can transport a signal carrying information.
Topics discussed in this section:
 Network Criteria
 Physical Structures
 Categories of Networks

 Performance
 Depends on Network Elements
 Measured in terms of Delay and Throughput
 Reliability
 Failure rate of network components
 Measured in terms of availability/robustness
 Security
 Data protection against corruption/loss of data due to:
 Errors
 Malicious users
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Network Criteria

 Type of Connection
 Point to Point - single transmitter and receiver
 Multipoint - multiple recipients of single transmission
 Physical Topology
 Connection of devices
 Type of transmission - unicast, mulitcast, broadcast
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Physical Structures

1.17
Figure 1.3 Types of connections: point-to-point and multipoint

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Figure 1.4 Categories of topology

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Figure 1.5 A fully connected mesh topology (five devices)

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Figure 1.6 A star topology connecting four stations

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Figure 1.7 A bus topology connecting three stations

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Figure 1.8 A ring topology connecting six stations

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Figure 1.9 A hybrid topology: a star backbone with three bus networks

 Local Area Networks (LANs)
 Short distances
 Designed to provide local interconnectivity
 Wide Area Networks (WANs)
 Long distances
 Provide connectivity over large areas
 Metropolitan Area Networks (MANs)
 Provide connectivity over areas such as a city, a campus
1.24
Categories of Networks

Figure 1.10 An isolated LAN connecting 12 computers to a hub in a closet
1.25

1.26
Figure 1.11 WANs: a switched WAN and a point-to-point WAN

Figure 1.12 A heterogeneous network made of four WANs and two LANs
1.27

1.28
1-3 THE INTERNET
The Internet has revolutionized many aspects of our daily
lives. It has affected the way we do business as well as the
way we spend our leisure time. The Internet is a
communication system that has brought a wealth of
information to our fingertips and organized it for our use.
Organization of the Internet
Internet Service Providers (ISPs)

1.29
Figure 1.13 Hierarchical organization of the Internet

1.30
1-4 PROTOCOLS
A protocol is synonymous with rule. It consists of a set of
rules that govern data communications. It determines
what is communicated, how it is communicated and when
it is communicated. The key elements of a protocol are
syntax, semantics and timing
 Syntax
 Semantics
 Timing

 Syntax
 Structure or format of the data
 Indicates how to read the bits - field delineation
 Semantics
 Interprets the meaning of the bits
 Knows which fields define what action
 Timing
 When data should be sent and what
 Speed at which data should be sent or speed at which it is being
received.
1.31
Elements of a Protocol

Lec1 :- Data communication and network

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