Communications

Question 1

What is Baud Rate?

Answer 1

The number of signal changes in the medium per second

Question 2

What is Bit Rate?

Answer 2

The number of bits that are transmitted over the medium per second

Question 3

How do you calculate Bit Rate?

Answer 3

Bit Rate = Baud Rate x Number of Bits Per Signal

Question 4

What is Bandwidth?

Answer 4

Bandwidth is the range of frequencies that a communication medium is capable of transmitting

Question 5

What is the relationship between Bandwidth and Bit Rate?

Answer 5

The higher the bandwidth, the higher the bit rate

Question 6

What is Latency?

Answer 6

The difference in time between an action being initiated and its effect being noticed

Latency increases with distance

Question 7

What is a protocol?

Answer 7

A set of rules for the transmission of data across a network

Question 8

What is Serial Data Transmission?

Answer 8

When data is sent one bit at a time over one communication line

Question 9

When is Serial Data Transmission used?

Answer 9

For transmitting data from medium to long distances , such as connecting your mouse to your computer

Question 10

What is Parallel Data Transmission?

Answer 10

When data is sent using numerous parallel communication lines to send multiple bits between components in a computer simultaneously

Question 11

What is skewing?

Answer 11

Skewing occurs in Parallel Data Transmission

Each of the communication lines in the parallel communication medium will have slightly different electrical properties, meaning the time taken for one bit to be transferred will differ from line to line

This means the bits may not be received together

Question 12

How does skewing lead to corruption of data?

Answer 12

The higher the distance to travel, the higher the chance of skewing. This can lead to bits from different pulses overlapping, which causes corruption of data

Question 13

What is crosstalk?

Answer 13

Crosstalk is another issue with parallel data transmission

When communication lines are tightly packed, signals can leak from one line to another - which causes data corruption

Question 14

What are the advantages of Serial Data Transmission over Parallel? (4)

Answer 14

Parallel Data Transmission requires more wires, which means it is more expensive and more difficult to install

Serial is more reliable as it has no risk of skewing or crosstalk, unlike Parallel - which means there is less chance of data being corrupted

Question 15

When is Parallel Data Transmission used?

Answer 15

To connect parts within the processor

Question 16

What is Synchronous Data Transmission?

Answer 16

When data is sent at regular intervals and is received in the same order as it is sent
It is timed by the clock signal inside of the processor

Question 17

When is Synchronous Data Transmission used?

Answer 17

To send data between the buses during the Fetch Execute Cycle

Question 18

What is Asynchronous Data Transmission?

Answer 18

When data is sent as soon as it is available. Each byte contains a start and stop bit so its known when the data arrives so the next byte can be sent
(The Start Bit is always the opposite of the Stop bit)
It also contains a parity bit for error checking

Question 19

What are the conditions required for Asynchronous Data Transmission?

Answer 19

The sender and receiver must have the same baud rate

Question 20

What is a Star Network Topology?

Answer 20

When each client has its own direct connection to the central hub. The hub receives all packets and distributes them to the correct recipient

A server can be added in the same way a client is

Question 21

What are the advantages of a Star Network Topology?

Answer 21

1) Other clients can’t see packets that aren’t intended for them as each client as its own wire connection - so packets go directly to the recipient
2) Easy to add or remove Clients
3) Each cable only has one client connected to it - means collisions can’t occur
4) The failure of one cable doesn’t affect the rest of the network

Question 22

What are the disadvantages of a Star Network Topology?

Answer 22

1) If the Central Hub falls, then all communication across the network is stopped
2) Expensive to install due to the large amount of cables required

Question 23

What is a Bus Network Topology?

Answer 23

All clients are connected to a single cable called the backbone
A terminator is placed at the end of the backbone

There is no central hub and a server can be connected just like a client

Question 24

What are the advantages of a Bus Network Topology?

Answer 24

1) No Central Hub - This decreases the chance of failure and also lowers the cost of installing
2) Cheaper as fewer cables are required

Question 25

What are the disadvantages of a Bus Network Topology?

Answer 25

1) Packets are sent through a shared backbone - allowing every client on the network to see packets, even if they aren't intended for them 2) Backbone is used by multiple clients - increases the chance of collisions 3) Should the backbone fall, the whole network is unusable

Question 26

What is a server?

Answer 26

A piece of hardware which provides services such as file storage, internet and printer sharing

Question 27

What is a client-server network?

Answer 27

When one or more central servers provide services to the clients on the network The clients request services and the server responds with the services Services include file storage, email management, user accounts and more

Question 28

When are client-server networks used?

Answer 28

In Schools, Colleges or Businesses

Question 29

What are the advantages/disadvantages of Client-Server Networks?

Answer 29

Advantages: Provide security for the clients on the network Disadvantages: Very Expensive to Setup Require great expertise to setup

Question 30

What are Peer to Peer Networks?

Answer 30

Networks with no central server but instead the clients provide the services. Each client has equal status. One client may control emails, one client may control storage, etc

Question 31

What is the disadvantage of Peer to Peer Networks?

Answer 31

All clients which provide services must be running in order for the server to be fully operational (E.g. If the storage client doesn't work, then nobody can access their files)

Question 32

What are the advantages of Peer to Peer Networks?

Answer 32

Peer to Peer networks are more cost effective as there is no server required Peer to Peer Networks are easier to setup and maintain

Question 33

What is WPA/WPA2 (WIFI)

Answer 33

WIFI Protected Access - Requires the client to enter a password to enter a network

Question 34

What is disabling SSID Broadcast?

Answer 34

A method of securing a wireless network SSID (Service Set Identifier) is the name that identifies a Wireless network. Disabling the SSID broadcast stops wireless devices in the range of the network from displaying that it is available - meaning only people that know the SSID can get in

Question 35

What is a MAC Address Filter?

Answer 35

A method of securing a wireless network MAC addresses are assigned to every wireless device and are unique to that device - they are used as a method of identification Wireless networks can create a whitelist to only allow specific MAC Addresses into the network or can create a blacklist to ban specific MAC Addresses from a network This can be used to control who can use a wireless network

Question 36

What is CSMA/CA?

Answer 36

A protocol used in wireless networks to avoid data collisions caused by multiple devices communicating simultaneously.

Question 37

How does CSMA/CA work?

Answer 37

1) When a wireless device is ready to transmit data, it checks to see if the communication channel is idle -if it is, then the data is sent 2) If the channel is busy then it waits a random time before checking again 3) An extra protocol is added called RTS/CTS (Request to Send/Clear to Send) is used 4) Once the transmitting device has checked whether the channel is idle - it sends a request to send 5) If the server is idle, it will respond with a clear to send message - then communication begins between the device and server 6) If no Clear to Send Message is received, then the server is communicating with a hidden node and the transmitting device must wait before starting the process again

Question 38

What is a hidden node?

Answer 38

CSMA/CA only works in small networks - as it can't overcome hidden nodes. Hidden Nodes is a problem that occurs during the device checking for an idle channel. The device can't see some areas of a network where network communication is occurring - so data may be sent even if it isn't clear