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