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 Elements

Communication Devices

Electronic Communication Methods

Transmission Media

DATA COMMUNICATION SYSTEM ELEMENTS

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)

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)

How many types of Ethernet?

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

COMMUNICATION DEVICES

Email

Instant Messaging

Electronic communication methods

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

Transmission media

• 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

Both can transmit up to 100 Mbps

Cost

Typically, STP is more expensive

Connector

Both use RJ-45 connectors (see Figure 4-27) and data jacks

Noise immunity

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 fiber

Carries light pulses along single path

Multimode 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 FLAWSLatency

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

Electromagnetic interference (EMI)

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