1.3 Data Transmission

Question 1

What are the two types of transmission?

Answer 1

1. Serial transmission
2. Parallel transmission

Question 2

What is serial transmission?

Answer 2

Data sent bit-by-bit along the same data line.

Question 3

What is parallel transmission?

Answer 3

All bits in bytes are sent simultaneously along separate data lines.

Question 4

State 4 advantages for serial transmission.

Answer 4

1. Cheaper and easier to setup.
2. Requires only two wires rather than 8 or 16.
3. Less prone to interference over long distances
4. Simpler interface/circuit board.

Question 5

State a disadvantage for serial transmission.

Answer 5

Only one bit can be transmitted at a time so transmission times can be longer.

Question 6

State an advantage for parallel transmission.

Answer 6

Transmission can be completed in a shorter time (faster).

Question 7

State 2 disadvantages for parallel transmission.

Answer 7

1. Hardware is more expensive.
2. Prone to interference over a long distance.

Question 8

State 3 mode of transmission.

Answer 8

1. Simplex
2. Half-duplex
3. Full-duplex

Question 9

Explain simplex.

Answer 9

Data can travel in one direction e.g. radio.

Question 10

Explain half-duplex.

Answer 10

Data can travel in both directions but not at the same time e.g. walkie talkie.

Question 11

Explain full-duplex.

Answer 11

Data can travel in both directions at the same time e.g. phone.

Question 12

What is multiplexing?

Answer 12

Allows multiple signal sources to send data along the same communication medium/wire.

Question 13

What is switching?

Answer 13

A device forwards a packet of data towards their destination via a range of devices. It goes one step at a time to its destination.

Question 14

State 7 things that a packet contains.

Answer 14

1. Length
2. Packet ID
3. Source Address
4. Destination Address
5. Protocol
6. Data
7. Checksum

Question 15

Explain Length.

Answer 15

Number of bits in the packet.

Question 16

Explain Packet ID.

Answer 16

Unique identifier.

Question 16

Explain Source address.

Answer 16

IP address of the device sending the packet.

Question 17

Explain Destination address.

Answer 17

IP address of the device receiving the packet

Question 18

Explain protocol.

Answer 18

Saying which protocol has been used to form the packet.

Question 19

Explain data.

Answer 19

Bulk of the packet. Eventually everything else is discarded

Question 20

Explain Checksum.

Answer 20

Validation to check data sent matched data received.

Question 21

State 3 reasons why packet switches are used.

Answer 21

1. Better security as it is very difficult to intercept.
2. Makes more efficient use of data lines as there is no waiting during gaps.
3. Less likely to be affected by network failure because multiple paths are used.

Question 22

When does a collision occur?

Answer 22

When two transmissions attempt to use the same connection medium at the same time.

Question 23

How are collisions dealt with? (4)

Answer 23

1. It generates a frequency that can be detected by all connected devices.
2. Devices sending data detect this frequency and are told their transmissions have failed.
3. They each wait a randomly generated length of time before reattempting the transmission.
4. If another collision occurs this process is repeated.

Question 24

What are the two types of routing?

Answer 24

1. Static Routing 2. Dynamic Routing

Question 25

What is static routing?

Answer 25

Each router has access to a table which tells them which path to forward data depending on the destination address.

Question 26

State a disadvantage for static routing.

Answer 26

Although it is simple to run, it is not suitable for networks that changes often or often have devices added.

Question 27

What is dynamic routing?

Answer 27

Each router learns the location of other devices based on monitoring sources and destination addresses of data that is forwarded.

Question 28

State an advantage for dynamic routing.

Answer 28

(Follow up from before) This means changes to the network would be automatically identified by the router.

Question 29

What is a router?

Answer 29

A router is a device in a network which holds information about addresses of computers in the network (or other networks).

Question 30

What do routers do? (3)

Answer 30

1. Can direct data to the correct computer 2. Can direct data around a network in the most efficient way. 3. Act as a gateway connecting to a larger network.

Question 31

State 3 advantages of digital transmission over analogue.

Answer 31

1. Digital transmission is preferred as it less likely to suffer from corruption. 2. Can error check data. 3. Can compress data and therefore transfer time is quicker.