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 conceptsd) Define common transmission flaws affecting

data signals.e) Define rules of communicationsf) Explain the signal transmission

Data ElementsCommunication DevicesElectronic Communication MethodsTransmission Media

DATA COMMUNICATION SYSTEM ELEMENTS

DATA ELEMENTS

MessageSenderReceiverMediumProtocol

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

EmailInstant Messaging

Electronic communication methods

Guided MediaTwisted-Pair CableCoaxial CableFiber Optic Cable

Unguided Media: WirelessTransport 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-PairConsists of one or more insulated wire pairs

encased in a plastic sheathDoes not contain additional shieldingTo 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 CableContains one or several glass fibers at its

coreSurrounding the fibers is a layer of glass called

cladding

Single-mode fiberCarries light pulses along single path

Multimode fiberMany pulses of light generated by LED travel

at different angles

Unguided Media: WirelessInfrared 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 transmissionRadio frequency (RF) transmission relies on

signals broadcast over specific frequenciesTwo most common RF technologies:

NarrowbandSpread spectrum

DATA TRANSMISSION CONCEPTS

Analog and digital signalingData modulationSimple, half-duplex and full-duplexMultiplexingPoint-to-point transmissionBroadcast transmissionBluetooth, 3GThroughputBandwidth

TRANSMISSION FLAWS

NoiseOccurred when devices act as a sending antenna

and the transmission medium act as the receiving antenna.

AttenuationLoss of signal strength as transmission travels

away from sourceAnalog 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

DistortionSignal changes its form or shape.Made of different frequencies.

RegenerationProcess of retransmitting a digital signal

RepeaterDevice used to regenerate a signal

A digital signal distorted by noise, and then repeated