Unit 2.1 - types and methods of data transmission

Question 1

Describe the structure of a data packet

Answer 1

1. Header - senders and receivers IP addresses, packet number. Essential for reconstruction of og message
2. Payload - data/part of message
3. Trailer - bits to show end of packet

Question 2

Why is data broken down into packets?

Answer 2

Allows it to be transmitted faster

Question 3

What is packet switching?

Answer 3

A mode of data transmission when the data is broken down into parts/packets and sent independently over different routes, depending on which are the least congested and will therefore allow it to arrive the fastest. Packets may arrive out of order and will be reassembled on arrival.

Question 4

Name 1 advantage and 1 disadvantage of packet switching

Answer 4

Advantage - packets can take different routes to get to destination. This means that they can be delivered even if one route is unavailable. Router can determine the best route for each packet. Transmission errors can be detected when they occur, and packets can be requested to be resent
Negative - packets may be dropped if they move around the network for a certain period of time without being delivered

Question 5

Name and explain 2 methods of data transmission

Answer 5

1. Serial transmission - a single wire is used to connect the sending and receiving devices. Bits are sent one at a time. Used over long distances.
2. Parallel transmission - multiple wires are used to connect the sending and receiving device. Multiple bits are sent at the same time. Used over short distances.

Question 6

Explain the advantages and disadvantages of serial data transmission

Answer 6

Advantage - more reliable over long distances (less likely for bits to get lost during transmission). Arrive in order. Low cost
Disadvantage - slower than parallel transmission

Question 7

Explain advantages and disadvantages of parallel transmission

Answer 7

Advantage - faster transmission
Disadvantage - bits may arrive out of order and need to be rearranged. Expensive to implement over longer distances, so only used for short distances. Prone to interference.

Question 8

Name 3 types of data transmission

Answer 8

1. Simplex - only one device can transmit data; data moves in one direction via single cable.. Example : from computer to printer
2. Half-duplex - both receiving and sending device can transmit data, but not at the same time. Data can move in both directions down a single cable, but not at the same time. Example : walkie-talkie
3. Full-duplex - receiving and sending side can send and receive data at the same time; data is transmitted simultaneously in both directions using two communication channels. Example : online video game

Question 9

Define interface

Answer 9

A shared boundary or place where devices can link up and share information

Question 10

Define USB and advantages

Answer 10

A universal serial bus is a communication interface used to connect devices to a computer over a short distance. Uses serial transmission. Can be half-duplex or duplex.
Advantages : it is universal used in most common devices. Can transfer power and data at the same time. Backwards compatibility, meaning that newer USB models work with older USB interfaces.