Data Communication and Networking

1. Chapter 1
Introduction
DATA COMMUNICATION
AND NETWORKS IT-212
Ehtesham Raza
Assistant Professor
Govt. Murray College Sialkot

2. 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.
 Components of a data communications system
 Data Flow
Topics discussed in this section:

3. Figure 1.1 Components of a data communication system
1. Message
2. Sender
3. Receiver
4. Transmission
Medium
5. Protocol

4. Data Representation
Data
Text Number Images Audio Video

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

6. 1-2 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.
 Network Criteria
 Physical Structures
 Categories of Networks
Topics discussed in this section:

7. Network Criteria
• 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

8. Physical Structures
• 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

9. Connection Types and Transmission Types

10. Network Types
• 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

11. Local Area Network (LAN)
A local area network (LAN) is
usually privately owned and
connects some hosts in a single
office, building, or campus.
Each host in a LAN has an
identifier, an address, that
uniquely defines the host in the
LAN. A packet sent by a host to
another host carries both the
source host’s and the destination
host’s addresses.

12. Network Topologies
Network Topology is the schematic description of a
network arrangement, connecting various nodes(sender
and receiver) through lines of connection.
Topologies
Bus Star Ring Mesh Tree

13. Bus and Star Topologies

14. Ring and Mesh Topologies

15. Wireless LAN (WLAN)
A wireless local area network (WLAN) provides wireless
network communication over short distances using radio
or infrared signals instead of traditional network cabling.

16. Wide Area Network (WAN)
A wide area network (WAN) has a wider geographical span,
spanning a town, a state, a country, or even the world. WAN
interconnects connecting devices such as switches, routers, or
modems. WAN is normally created and run by communication
companies and leased by an organization that uses it.
Types of WAN:
1. Point-to-point WANs
A point-to-point WAN is a network that connects two
communicating devices through a transmission media (cable or
air).

17. A switched WAN is a combination of several point-to-point
WANs that are connected by switches.
2. Switched WANs

18. INTERNETWORK or INTERNET
When two or more networks are connected, they make an
internetwork, or internet
An internet (note the lowercase i) is two or more networks that can
communicate with each other. The most notable internet is called
the Internet (uppercase I ), and is composed of thousands of
interconnected networks.

19. THE INTERNET
The Internet consists of several backbones, provider networks, and
customer networks.
At the top level, the backbones are large networks owned by some
communication companies such as Sprint, Verizon (MCI), AT&T,
and NTT. The backbone networks are connected through some
complex switching systems, called peering points.
At the second level, there are smaller networks, called provider
networks, that use the services of the backbones for a fee.
The customer networks are networks at the edge of the Internet that
actually use the services provided by the Internet. They pay fees to
provider networks for receiving services.

20. HIERARCHICAL STRUCTURE OF THE INTERNET

21. SWITCHING
An internet is a switched network in which a switch connects at
least two links together. A switch needs to forward data from a
network to another network when required.
CIRCUIT-SWITCHED NETWORK
In a circuit-switched network, a dedicated connection, called a
circuit, is always available between the two end systems; the
switch can only make it active or inactive.

22. PACKET-SWITCHED NETWORK
In a computer network, the communication between the two ends
is done in blocks of data called packets. Instead of the continuous
communication there is exchange of individual data packets
between the two computers. This allows to make the switches
function for both storing and forwarding.

23. 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
Topics discussed in this section:

24. Elements of a Protocol
• 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.