2.1 Data Transmission

Question 1

what are packets

Answer 1

broken down peices of data sent seperately to increase efficiency

Question 2

what are the advantages of packets (2)

Answer 2

• smaller data is easier to handle than one long stream of data
• each packet can go a seperate route which can reduce ineffiency if one route becomes busy or goes down

Question 3

what are the disadvantages of packets

Answer 3

• require careful construction and additional information so it can be reassembled at the destination

Question 4

what are the 3 components of a packet

Answer 4

the packet header
the payload
the trailer

Question 5

what is a packet header (3)

Answer 5

a part of the packet container the senders ip adress, the recieveres ip adress, and the packet sequence number

Question 6

what is a payload

Answer 6

the part of the packet that contains the actual data being transmitted

Question 7

what is the trailer

Answer 7

part of the packet which marks the end of a packet

Question 8

what is packet switching

Answer 8

the process where data is broken down into packets and sent to the most efficient route possible by the router to be recieved by the reciever where at the destination it will be reorded correctly

Question 9

what are the 5 stages of packet switching

Answer 9

• a data transmission is broken down into packets
• each packet is assigned a sequence number before being sent
• each packet takes its own route based on conjestion
• routers are responsible for controlling the route each packet takes
• packets arrive out of order and are re assembled at the destination in order

Question 10

what are the advantages of packet switching (4)

Answer 10

no need to tie up a single communications channel
easy to overcome busy routes
relatively easy to expand package usage
possible to achieve a high data transmission rate

Question 11

disadvantages of packet switching

Answer 11

-packets can become lost
-realtime streaming is more prone to errors
-delays at the destination while packets are being reordered

Question 12

what are the 3 types of data transmission

Answer 12

simplex, duplex, and half-duplex

Question 13

what is simplex data transmission

Answer 13

a transmission type which allows only one direction for traffic to move

Question 14

where is simplex data transmission used

Answer 14

from computer to printers
from computers to speakers

Question 15

what is half duplex transmission

Answer 15

a transmission type which allows data to be transferred in both directions but not at the same time

Question 16

where is half duplex transmission used

Answer 16

parralel printer cables, computer sends file THEN printer says “ink low”
walkie talkies

Question 17

what is full-duplux transmission

Answer 17

the most common transmission type which allows data to be transmitted to both directions at the same time

Question 18

where is full duplex used

Answer 18

network cables
accross lans and internet

Question 19

what are the TWO types of data transmission

Answer 19

serial and parralel data transmission

Question 20

what is serial data transmission

Answer 20

when bits are sent along one transmission medium one at a time

Question 21

what is parralel data transmission

Answer 21

when data bits is sent along multiple transmission mediums simeualtanously

Question 22

what are the advantages and disadvantages of serial (4)

Answer 22

pros
- simple and low cost
- reliable over long distances
- low interference and margin for error
cons
- low transmission speeds

Question 23

what are the pros and cons of parralel

Answer 23

pros
- fast transmission speeds
- data can be sent both distances
cons
- can only be used over short distances
- very prone to interefence if a bit is sent late

Question 24

what is skew

Answer 24

when bits are sent out of error due to slow transmission or microscopic speed diferences in wires when transmitting the bits, causing the bits to be out of sync

Question 25

What are data buses

Answer 25

mediums of transmissions used to transmit data, used internally aswell by computers to transmite data from IC to IC, integrated circuits

Question 26

what is USB

Answer 26

universal serial bus, a common input/output databus using serial transmission which supports full and half duplex transmission

Question 27

how many wires are there in a USB cable

Answer 27

4

Question 28

what does each wire do in a USB cable

Answer 28

black wire - for earthing, power red wire - for power white/green wire - used to send data in 2 seperatre directions

Question 29

what are the advantages of USB (6)

Answer 29

- has became an industry standard, very well supported - supplies its own 5V power - devices connected via USB are automatically connected along with appropraite device drivers - designed to be backwards compatible, so older versions can connect - USB hubs can be used to add extra ports - USB protocol can notify the transmitting device to retransmit data if there is an error

Question 30

cons of USB (3)

Answer 30

limited distance of around 5m can be extended but only with additional hardware, usb hubs etc backwarsd compatibility is becoming increasingly rare transfir limitations, even newer versions like USB-C and 3.0 are slower than ethernet