2.1 Types and methods of data transmission

Question 1

What are packets?

Answer 1

Packets are small chunks of information/data

Question 2

The structure of a data packet
A data packet has three sections:

Answer 2

1. Packet Header
2. Payload
3. Packet Trailer

Question 3

The packet header includes the:

Answer 3

– destination IP address
– packet number
– source/originator’s IP address
– error checker

Question 4

Payload contains:

Answer 4

the actual data

Question 5

Packet Trailer contains:

Answer 5

• Additional error checks
• End of packet notification (Includes a method of identifying the end of the packet)

Question 6

Packet switching

Answer 6

Method of data transmission-
- the data is broken into multiple packets
- Packets are then sent independently from start to end and reassembled at the receiver’s computer.

Question 7

Describe how packet switching is used and how it can be protected from corruption?

Answer 7

1. The data is first broken down into packets which are given a source address (where its come from) and a destination address (where its going to) [1]
2. Each packet receives a packet number so that the data can be reassembled when it reaches its destination [1]
3. Each packet also receives an error check such as a parity bit. A parity bit checks whether any bits have been flipped due to corruption [1]
4. Each packet is sent over the internet via routers. Routers contain routing tables that determine the next closest router to the destination [1]
5. Packets may take different routes depending on internet traffic and arrive at their destination in any order [1]
6. Packets are checked for errors using the error checks
7. missing packets can be requested to be resent [1]
8. Once all packets have been received then they can be put together in order using the packet numbers [1]
9. Once assembled the data can be read by the reciever

Question 8

The advantages of packet switching are:

Answer 8

1. The whole file doesn’t need to be resent if a corruption occurs, only the individual packets that were corrupted need to be resent. This saves time and internet bandwidth
2. High transmission rates
3. It’s harder to hack an individual’s data as each packet contains minimal data, and travels through the network separately
4. Possible to overcome failed or busy nodes

Question 9

The disadvantages of packet switching are:

Answer 9

1. Packets may be lost
2. Delay at the receiver while the packets are being re-ordered
3. not support real-time streaming

Question 10

Types of data transmission

Answer 10

Serial data transmission
Parallel data transmission

Question 11

Serial data transmission

Answer 11

One bit is sent at a time across a single wire
e.g. USB

Question 12

Serial trasnmission ad and drawback

Answer 12

advantages:
* The data will arrive in the order it is sent
* It is less likely to have errors
* Serial transmission is cheap over short and long distances as the cost of wire is fairly inexpensive
* works well over long distances

drawback:
* low speed transmission

Question 13

Parallel data transmission

Answer 13

Multiple bits are sent at a time across several wires

Question 14

Parallel transmission ad and drawbacks

Answer 14

advantages:
* fast data transmission
* works well over short distances

drawbacks:
* expensive
* can cause delays

Question 15

(Direction of transmission) Transmission Modes

Answer 15

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

Question 16

Simplex transmission mode

Answer 16

data can be sent unidirectional and travel in only one direction
from computer to printer
from computer to monitor

Question 17

Half-duplex transmission mode

Answer 17

data transmissions are bidirectional i.e. can travel in both directions, but not simultaneously (at the same time)
e.g. walkie-talkie

Question 18

Full-duplex transmission mode

Answer 18

transmissions are bidirectional at the same time
e.g. telephone call, video conferencing

Question 19

Full form of USB

Answer 19

Universal Serial Bus

Question 20

USB advantages

6

Answer 20

• Devices are automatically detected and drivers are automatically downloaded
• Cannot be inserted incorrectly
• industry standard
• Supports different transmission speeds
• fast transmission rate
• are backwards compatible with older USB standards

Question 21

USB drawbacks

Answer 21

• The maximum cable length is roughly 5 metres meaning it cannot be used over long distances, limiting its use
• presently, the meaximum transmission rate is less than 500 megabits pepr second
• the older usb version may not be supported in the future