PHYSICAL LAYER

Question 1

PURPOSE OF THE PHYSICAL LAYER

Answer 1

• TRANSPORT BITS ACROSS THE NETWORK MEDIA
  -ACCEPTS A COMPLETE FRAME FROM THE DATA LINK LAYER AND ENCODES IT AS A SERIES OF SIGNALS THAT ARE TRANSMITTED TO LOCAL MEDIA

Question 2

WHAT IS ENCODING?

Answer 2

CONVERTS THE STREAM OF BITS INTO A FORMAT RECOGNAZABLE BY THE NEXT DEVICE IN THE NETWORK LAYER. ITS PROVIDES THE PREDICTABLE PATTERNS THAT CAN BE RECOGNIZED BY NEXT DEVICE.

Question 3

WHAT IS SIGNALING?

Answer 3

METHOD OF HOW THE BIT VALUES ‘1’ AND ‘0’ ARE REPRESENTED ON THE PHYSICAL MEDIUM.

Question 4

WHAT IS BANDWIDTH?

Answer 4

CAPACITY AT WHICH A MEDIUM CAN CARRY DATA

Question 5

CHARACTERISTICS OF COPPER CABLING?

Answer 5

-COMMON TYPE OF CABLING USED.
-INEXPENSIVE AND EASY TO INSTALL
-LOW RESISTANCE TO ELECTRICAL CURRENT FLOW

Question 6

LIMITATION OF COPPER?

Answer 6

1. ATTENUATION-LONGER ELECTRICAL SIGNALS TRAVEL, THE WEAKER THEY GET.
2. ELECTRICAL SIGNAL IS SUSCEPTIBLE TO INTERFERENCE FROM 2 SOURCES-CAN DISTORT AND CORRUPT THE DATA SIGNALS (EMI) AND (RFI) AND CROSSTALK.

Question 7

WHAT IS THE MITIGATION OF COPPER?

Answer 7

-STRICT ADHERENCE TO CABLE LENGTH LIMITS (MITIGATE THE ATTENUATION)
-USING METALLIC SHIELDING AND GROUNDING (MITIGATE THE EMI AND RFI)
-TWISTING OPPOSING CIRCUIT PAIR WIRES 2GETHER (MITIGATE CROSSTALK)

Question 8

TYPES OF COPPER CABLING?

Answer 8

1. UTP -UNSHIELDING TWISTED-PAIR CABLE
2. STP -SHIELDED TWISTED-PAIR CABLE
   3.COAXIAL CABLE

Question 9

KEY CHARACTERISTICS OF UTP?

Answer 9

1. OUTER JACKETS- PROTECTS THE COPPER WIRES FROM PHYSICAL DAMAGE
2. TWISTED PAIR- PROTECT THE SIGNAL FROM INTERFERENCE
3. COLOR-CODED PLASTIC - ISOLATES THE WIRES FROM EACH OTHER AND IDENTIFIES EACH PAIR.

Question 10

KEY CHARACTERISTICS OF STP?

Answer 10

1. OUTER JACKET-PROTECTS THE COPPER WIRES FROM PHYSICAL DAMAGE
   2.BRAIDED/FOIL SHIELD- PROVIDES EMI/RFI PROTECTION
2. FOIL SHIELD FOR EACH PAIR OR WIRES- PROVIDE EMI/RFI PROTECTION
   4.COLOR-CODED PLASTIC - ISOLATES THE WIRES FROM EACH OTHER AND IDENTIFIES EACH PAIR.

Question 11

KEY CHARACTERISTICS OF COAXIAL CABLE?

Answer 11

1.OUTER JACKET-PROTECTS THE COPPER WIRES FROM PHYSICAL DAMAGE
2.METALLIC FOIL- 2ND WIRE IN THE CIRCUIT & SHIELD FOR INNER CONDUCTOR
3.COPPER CONDUCTOR- TRANSMIT THE ELECTRONIC SIGNALS

Question 12

TYPES OF CONNECTORS USED WITH COAXIAL CABLE?

Answer 12

1. WIRELESS INSTALLATIONS- ATTACH ANTENNA TO WIRELESS DEVICES
2. CABLE INTERNET INSTALLATIONS-CUSTOMER PREMISES WIRING

Question 13

WHY UTP CABLE IS TWISTED?

Answer 13

EACH PAIR HAS OPPOSITE POLARITY. ONE IS -VE AND ANOTHER IS +VE. WHEN THEY TWISTED TO EACH OTHER, THE MAGNETIC FIELDS EFFECTIVELY CANCEL EACH OTHER AND OUTSIDE EMI/RFI

DIFFERENT AMOUNT OF TWISTING PREVENT CROSSTALK AMONGST THE WIRES IN THE CABLE.

Question 14

WHAT IS PROPERTIES OF FIBER-OPTIC CABLING?

Answer 14

1.TRANSMITS DATA OVER LONGER DISTANCES AT HIGHER BANDWIDTH THAN ANY OTHER NETWORKING MEDIA.
2. IMMUNE TO EMI/RFI.
3. USES LASER OR LED TO ENCODE BITS AS PULSES OF LIGHT
4. ACTS AS WAVE GUIDE TO TRANSMIT LIGHT BETWEEN TWO ENDS WITH MINIMAL SIGNAL LOSS

Question 15

TYPES OF FIBER MEDIA AND ADVANTAGES?

Answer 15

1. SINGLE-MODE FIBER - VERY SMALL CORE, LDR APPLICATIONS
2. MULTIMODE FIBER -LARGER CORE,LED TRANSMIT AT DIFFERENT ANGLES

Question 16

FIBER OPTICS CABLE USAGE?

Answer 16

1. ENTERPRSE NETWORKS - BACKBONE CABLING APPLICATIOND AND INFRASTRUCTURE DEVICES
2. FIBER-TO-THE-HOME - PROVIDE ALWAYS ON BROADBAND SERVICES TO HOMES
3. LONG-HAUL NETWORKS- SERVICE PROVIDERS TO CONNECT COUNTRIES AND CITIES
4. SUBMARINE CABLE NETWORKS - PROVIDE RELIABLE HIGH-SPEED IN HARSH UNDERSEA ENVIRONMENTS AT UP TO TRANSOCENIC DISTANCES

Question 16

TYPES OF FIBER OPTIC CONNECTORS?

Answer 16

1. STRAIGHT-TIP (ST) CONNECTORS
2. LUCENT CONNECTOR (LC) SIMPLEX CONNECTOR
   3.SUBSCRIBER CONNECTOR (SC)
3. DUPLEX MULTIMODE LC

Question 17

LIMITATION OF WIRELESS MEDIA?

Answer 17

1. Coverage area- Effective coverage can be significantly impacted by the physical characteristics of the deployment location.
   2.Interference- Wireless is susceptible to interference and can be disrupted by many common devices.
   3.Security- Wireless communication coverage requires no access to a physical strand of media, (anyone can gain access to the transmission).
   4.Shared medium- WLANs operate in half-duplex, which means only one device can send or receive at a time. Many users accessing the WLAN simultaneously results in reduced bandwidth for each user.