Communication

Question 1

Baud rate

Answer 1

The number of signal changes per second

Question 2

Bit rate

Answer 2

• The number of bits that are transmitted per second
• Baud rate * number of bits per signal

Question 3

Bandwidth

Answer 3

The range of frequencies that a communication medium is capable of transmitting

Question 4

Latency

Answer 4

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

Question 5

Protocol

Answer 5

• A set of rules relating to communication between device
• Enables devices made by different manufacturers to communicate seamlessly

Question 6

Serial data transmission

Answer 6

• Data is sent one bit at a time over a single communication line
• Used for transmitting data over medium to long distances

Question 7

Parallel data transmission

Answer 7

• Numerous parallel communication lines that allows for multiple bits to be sent simultaneously
• Used for transmitting data over short distances

Question 8

Examples of data transmission

Answer 8

• Serial => USB
• Parallel => between parts of the processor

Question 9

Crosstalk

Answer 9

Signals from tightly packed communication lines can “leak” into other, causing data corruption

Question 10

Skew

Answer 10

• Each line in parallel transmission has slightly different electrical properties, leading to different times taken
• This means that bits sent together may not be received together, leading to bits being overlapping and the corruption of data

Question 11

Serial vs Parallel

Answer 11

• Serial data transmission does not suffer from skew or crosstalk, making it a more reliable communication method over long distances
• Serial mediums are cheaper to install

Question 12

Synchronous transmission

Answer 12

Data is sent on shared clock pulses at regular intervals, received in the same order that they were sent

Question 13

Uses of synchronous transmission

Answer 13

• Transmitting information in real-time systems
• Used by busses in the processor

Question 14

Asynchronous transmission

Answer 14

• Start and stop bits are used to indicated the duration of a transmission
• The sender and receiver must use the same Baud rate and synchronize their clocks for the duration of data transmission

Question 15

Physical star network topology

Answer 15

• Each client has its own direct connection to a central hub
• The hub receives packets for all clients and delivers them to the correct recipient

Question 16

Advantages of physical star network topology

Answer 16

• Packets are sent directly to the recipient so other clients cannot see packets that aren’t intended for them
• It is easy to add and remove clients to and from the network
• Each cable has just one device, removing the possibility of collisions
• The failure of one cable does not affect the rest of the network

Question 17

Disadvantages of physical star network topology

Answer 17

• If the central hub fails all communication is stopped
• Expensive to install due to the large amounts of cable

Question 18

Physical bus topology

Answer 18

• All devices are connected to a single central cable (the backbone)
• A terminator is at each end of the cable, preventing signals from bouncing back along the cable

Question 19

Advantages of physical bus topology

Answer 19

• No central hub, reducing the chance of a network failure
• Inexpensive to install due to minimum length of cable

Question 20

Disadvantages of physical bus topology

Answer 20

• Packets are sent through the shared backbone, allowing every client on the network to see packets that aren’t intended for them
• The backbone is used for communication by multiple clients, introducing the risk of collisions
• The entire network will fail if the backbone fails

Question 21

Logical network topology

Answer 21

The flow of data packets within a network

Question 22

Logical bus network

Answer 22

Delivers packets to all clients on the network

Question 23

Logical star network

Answer 23

Delivers packets only to their recipient

Question 24

Host

Answer 24

A device on a network that provides services

Question 25

Client-server networking

Answer 25

- A central server provides services to multiple clients - Allows for central management of clients and greater network security - Requires higher levels of expertise to set up and manage

Question 26

Peer-to-peer networking

Answer 26

- Services are provided by the clients themselves - They are more effective than client-server networking as there is no need for a powerful server - Easier to set up and maintain

Question 27

Wireless networking

Answer 27

- Allows clients to communicate within a network without being physically connected to it - Requires a wireless access point which connects to a wired network - Requires a wireless network adapter in each device that connects to the wireless network

Question 28

WiFi

Answer 28

- The standard that enables wireless local area networking - Allows devices to connect wirelessly to a network using radio signals - WiFi is based on international standards that enables global compatiblity

Question 29

Components required for wireless networking

Answer 29

- Network Interface Card (built into devices) - Wireless Access Point (sends and receives wireless signals) - Router (routes data to and from the internet) - Modem (connects the network to the wider internet)

Question 30

Methods of wireless network security

Answer 30

- WPA/WPA2 encryption - SSID Management - MAC Address Filtering

Question 31

WPA/WPA2 encryption

Answer 31

When a device tries to joins the network it must enter a pre-shared key

Question 32

SSID Management

Answer 32

- The SSID is the name of a wireless network - Broadcasting the SSID means it shows up when someone searches for it - Hiding the SSID stops it from being publicly visible

Question 33

MAC address filtering

Answer 33

- Every wireless device has a unique assigned MAC address - MAC address whitelists allow only specific devices to connect to a network - MAC address blacklists can be used to block specific devices from connecting to a network

Question 34

Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA)

Answer 34

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

Question 35

CSMA/CA process

Answer 35

- When a device is ready to transmit is listens to the communication channel to check whether it is idle - If so the data is transmitted. If not, the device waits a random period of time and checks again - An exponential backoff algorithm increases the time period for each check - It cannot overcome hidden nodes

Question 36

RTS/CTS

Answer 36

- A solution to the hidden node problem - The sender sends a "request to send" message to the server when the channel seems idle - If the server is idle it will respond with a "clear to send" message so transmission can begin - If no CTS message is received the server is busy communicating and the transmitting data must wait