Download TOPIC 1.2

TOPIC 1.2
INTRODUCTION TO
NETWORKING
OBJECTIVES
By the end of the topic, students should be able to:

a)
List the elements of data communication systems.
b)
Describe the communication devices:

Wired

Wireless
c)
Describe basic data transmission concepts
d)
Define common transmission flaws affecting data
signals.
e)
Define rules of communications
f)
Explain the signal transmission
DATA COMMUNICATION SYSTEM
ELEMENTS

Data Elements

Communication Devices

Electronic Communication Methods

Transmission Media
DATA ELEMENTS

Message

Sender

Receiver

Medium

Protocol
COMMUNICATION DEVICES


A hardware component that enables a computer
to send and receive data, instructions and
information and from one or more computers.
Type of communication devices:

Wired (Data Terminal Equipment (DTE))

Wireless (3G,GPRS, laptop, mobile phones)
COMMUNICATION DEVICES

Wired

Serial Wires are used for high end connectivity
between different devices and widely used on layer 3.

DTE ( data terminal equipment) and DCE (data
circuit-terminating equipment / data
communications equipment).

Ethernet Cables (UTP)
COMMUNICATION DEVICES

Wireless Devices
COMMUNICATION DEVICES

REPEATER ~ increasing the signals energy

HUB / SWITCH


Centralizing connection for all network devices

Sending packets using MAC address
BRIDGE ~ Connecting two or more different networks for
communication

ROUTER ~ Forwarding packets in the network using MAC and IP
address

GATEWAYS ~ a device that acts as a “MAIN PATH” for all network
traffics
Electronic communication methods

Email

Instant Messaging
Transmission media


Guided Media

Twisted-Pair Cable

Coaxial Cable

Fiber Optic Cable
Unguided Media: Wireless

Transport electromagnetic waves without using a
physical conductor
Transmission media

Twisted-Pair Cable
•
•
Color-coded pairs of insulated copper wires twisted
around each other and encased in plastic coating
Twists in wire help reduce effects of crosstalk
•
•
Number of twists per meter or foot known as twist ratio
Alien Crosstalk
•
When signals from adjacent cables interfere with another
cable’s transmission

Shielded Twisted-Pair (STP)

STP cable consists of twisted wire pairs that are
individually insulated and surrounded by shielding
made of metallic substance

Unshielded Twisted-Pair

Consists of one or more insulated wire pairs
encased in a plastic sheath

Does not contain additional shielding

To manage network cabling, it is necessary to be
familiar with standards used on modern networks,
particularly Category 3 (CAT3) and Category 5
(CAT5)
Comparing STP and UTP

Throughput


Cost


Both use RJ-45 connectors (see Figure 4-27) and data jacks
Noise immunity


Typically, STP is more expensive
Connector


Both can transmit up to 100 Mbps
STP is more noise-resistant
Size and scalability

Maximum segment length for both is 100 meters

Fiber-Optic Cable

Contains one or several glass fibers at its core

Surrounding the fibers is a layer of glass called cladding
 Single-mode

Carries light pulses along single path
 Multimode

fiber
fiber
Many pulses of light generated by LED travel at
different angles
Unguided Media: Wireless
Infrared
transmission
 Infrared networks use infrared
light signals to transmit data
through space
 Direct
infrared transmission
depends on transmitter and receiver
remaining within line of sight

In indirect infrared
transmission, signals can bounce
off of walls, ceilings, and any other
objects in their path

RF transmission

Radio frequency (RF) transmission relies on
signals broadcast over specific frequencies

Two most common RF technologies:

Narrowband

Spread spectrum
DATA TRANSMISSION CONCEPTS

Analog and digital signaling

Data modulation

Simple, half-duplex and full-duplex

Multiplexing

Point-to-point transmission

Broadcast transmission

Bluetooth, 3G

Throughput

Bandwidth
TRANSMISSION FLAWS

Noise


Occurred when devices act as a sending antenna and
the transmission medium act as the receiving
antenna.
Attenuation

Loss of signal strength as transmission travels away
from source

Analog signals pass through an amplifier, which
increases not only voltage of a signal but also noise
accumulated
An analog signal distorted by noise, and then amplified
TRANSMISSION FLAWS

Latency


Electromagnetic interference (EMI)


Latency is the delay between requesting data and the
receipt of a response, or in the case of one-way
communication, between the actual moment of a signal's
broadcast and the time it is received at its destination
Interference that may be caused by motors, power lines,
television, copiers, fluorescent lights, or other sources of
electrical activity
Radiofrequency interference (RFI)

Interference that may be generated by motors, power
lines, televisions, copiers, fluorescent lights, or
broadcast signals from radio or TV towers
TRANSMISSION FLAWS


Distortion

Signal changes its form or shape.

Made of different frequencies.
Regeneration


Process of retransmitting a digital signal
Repeater

Device used to regenerate a signal
A digital signal distorted by noise, and then repeated