09 Communication And Networking

Question 1

What is serial data transmission?

Answer 1

One cable is used and the bits are sent one after the other along it
Two lines are required for two way transmission

Question 2

What is parallel data transmission?

Answer 2

Parallel cables are a ribbon of several smaller cables
Several bits are sent at once along different channels however it has to wait until one set of data has been sent in order to send the next set

Question 3

What are the advantages of serial data transmission?

Answer 3

Only one line is required
They are reliable over very long distances at very high frequencies
Serial connectors are cheaper and smaller

Question 4

What are two problems with parallel data transmission?

Answer 4

Skew - As each wire has different properties, bits may travel slightly faster in one wire compared to another which causes skew

Crosstalk - It is the electromagnetic interference between two adjacent channels or parallel wires and gets more pronounced as frequency (speed of transmission) increases

Question 5

What are the advantages and disadvantages of parallel data transmission?

Answer 5

It is fast over a short distance such as inside computers

It can only be used in short distances of up to 2m
Liable to crosstalk and skew
Uses much more lines/cables

Question 6

Give an example of a serial and parallel connector

Answer 6

Serial - USB

Parallel - VGA

Question 7

What is synchronous data transmission?

Answer 7

All data transfers coincide with an internal clock pulse
Data is sent as one long stream or block of data with no gaps
Receiver counts the bits and reconstructs it

Question 8

What is asynchronous data transmission?

Answer 8

Each byte is sent separately the moment it is available

Each byte starts with a start bit and ends with a stop bit.

Question 9

How is a parity bit used in asynchronous data transmission?

Answer 9

It is added as the 8th bit and is used for error detection

Question 10

What are the advantages and disadvantages of asynchronous transmission?

Answer 10

It is relatively slow due to the increased number of bits being sent

It is a cheap and effective form of serial transmission well suited to low speed connections such as a mouse and keyboard

Question 11

What is latency?

Answer 11

The time delay between the moment the first byte starts and when it is received at its destination

Question 12

What is a protocol?

Answer 12

The set of rules relating to communication between devices

Two devices can be linked if they have the same protocol

Question 13

What does a protocol need to define?

Answer 13

Standards for physical connections and cabling
Rate of transmission (bit or baud rate)
Data format
Asynchronous or synchronous
Error checking procedures

Question 14

What is bit rate?

Answer 14

The number of bits transmitted in one second over a wired or wireless data link

Higher signal change means higher bit rate

Question 15

What is baud rate?

Answer 15

How many times a signal changes per second

Measured in megabits per second (Mbit/s

Question 16

What is baseband?

Answer 16

It carries one signal at a time. A bit is represent by high or low voltage

In baseband, bit rate is the same as baud rate and at each signal change one symbol is transmitted

Question 17

What is broadband?

Answer 17

It carries multiple signals on a fixed carrier wave and bits are sent as variations on the wave

Question 18

What is the relationship between bit and baud rate?

Answer 18

Bit rate = baud rate x number of bits per signal

Question 19

What is bandwidth?

Answer 19

The maximum capacity of a communications channel

Data transfer rate

Question 20

What is a local area network (LAN)?

Answer 20

Two or more computers connected together within a small geographical area (building)

Question 21

What is a network topology?

Answer 21

The arrangement of the devices which make up a computer network

Question 22

What is bus topology?

Answer 22

All nodes are connected to a single backbone cable
Each end has a terminator which stops signals bouncing back
Each node is passive
Data is sent in one direction at a time
Only one computer can transmit successfully at one time

Question 23

What are the advantages of a bus network?

Answer 23

Cheap to set up
Easy to add more devices
Good for small networks

Question 24

What are the disadvantages of a bus network?

Answer 24

If the main cable fails, everything fails
Limited cable length
Poor security
Low performance under heavy use due to data collisions

Question 25

What is Carrier sense multiple access with collision detection (CSMA/CD)?

Answer 25

It detects two nodes attempting to transmit at the same time
Both nodes stop and wait a random amount of time before transmitting again
Used in wired networks

CSMA/CA (Collision Avoidance) is used in wireless networks

Question 26

What is star topology?

Answer 26

Computers are connected to a central node which is either a hub or a switch

Question 27

What is a switch and what is a hub?

Answer 27

A switch sends each communication to the specific computer it is intended for. It uses MAC addressing

A hub broadcasts the message to every computer on the LAN

Question 28

What are the advantages of a star network?

Answer 28

Easy to isolate problems
Good performance
More secure if a switch is used as data is only sent to the recipient

Question 29

What are the disadvantages of a star networks?

Answer 29

Can be expensive to set up because of the length of cable required

If the central device fails everything else fails

Question 30

What is physical and logical topology?

Answer 30

Physical - How the devices are physically connected

Logical - How the devices communicate across the physical topologies

Question 31

What is a client-server network?

Answer 31

Server provides services or resources required by clients

Client requests services or resources

Suitable for small and big organisations but requires an IT specialist

Question 32

What does the server do in a client server network?

Answer 32

Manage security
Hold some files
Some processing tasks

Question 33

What is peer to peer networking?

Answer 33

No central server
All computer can see each other’s files and communicate with each other
If a computer is switched off data cannot be retrieved

Question 34

What are the advantages of cloud computing?

Answer 34

Some software does not have to be downloaded
Accessible from anywhere with anything
Automatic backup and doesn’t take any storage on the device

Question 35

What is the purpose of Wi-Fi and what is needed for it?

Answer 35

Wireless network which devices can connect to through the WAP (wireless access point)

Need an ISP, modem and wireless router, device with an NIC

Question 36

How does Wi-Fi work?

Answer 36

A station consists of a computer and a network interface card
Stations share a radio frequency channel
WAP requires a connection to a router and router requires a connection to the modem

Question 37

What is SSID?

Answer 37

Service set identifier

Identifies each network by a unique name

Question 38

How can u secure Wi-Fi connections?

Answer 38

WPA
WPA2
MAC address whitelist

Question 39

How does CSMA/CA work?

Answer 39

Assemble a frame
Is channel idle?
If no wait a random amount of time
If yes transmit data

Question 40

What is the hidden node problem?

Answer 40

Nodes A and B are hidden from each other but the WAP can hear them both

Question 41

What is CSMA/CA using RTS/CTS?

Answer 41

Assemble a frame
Is channel idle 
If no wait a random amount of time
If yes transmit RTS
Is CTS received?
If no wait a random amount of time and go back to is channel idle?
If yes transmit data