2. Data transmission

Question 1

how is data transmitted

Answer 1

it is broken down into packets to be transmitted

Question 2

what is the structure of a pcket

Answer 2

• packet header
• payload
• trailer

Question 3

what does the packet header include

Answer 3

• senders IP adress
• recievers IP adress
• Packet number

Question 4

describe the process of packet switching

Answer 4

• Data is broken down into packets
• Each packet could take a different route
• A router controls the route a packet takes
• Packets may arrive out of order
• Once the last packet has arrived, packets are
  reordered

Question 5

what are the 2 methods of transmission

Answer 5

serial
parralel

Question 6

what is serial transmission

Answer 6

serial transmission, a single wire is used to connect the sending device to the receiving device. Bits are transmitted one at a time.
it is reliable over long distance, less likely to get lost, wont arrive in wrong order, take long time

Question 7

parralel transmission

Answer 7

multiple wires are used to connect the sneding device and recievig device. several bits aee sent simultaneously. each bit travels through a seperate wire. it is faster but bits may arrive rearanged and can be expensive

Question 8

what are the 3 types of data transmission

Answer 8

simplex
half- duplex
full duplex

Question 9

what is simplex

Answer 9

only 1 device can transmit data in 1 direction only eg:files sent to be printes

Question 10

what is half duplex

Answer 10

data can be sent both directions but 1 at a time. eg: walkie talkies

Question 11

what is duplex

Answer 11

data can be sent forward and backwards simultaneously eg: online video game

Question 12

what is the universal serial bus

Answer 12

s a communication interface that has become a standard for connecting devices to their parent

Question 13

does the usb use serial or parralel

Answer 13

serial transmission- only 1 direction

Question 14

advantages of usb

Answer 14

• it is univeral
• can only be inserted a certain way
• compatible with many devices
• use other cables while using usb

Question 15

what is parity check

Answer 15

involves a parity bit at the end or start of binary number and is sent along with the data. there is an even parity or add parity ( refering to th enumbers of 1s)

Question 16

how to calculte checksum

Answer 16

if the sum of bytes is less than 255- that is the checksum
if not then
- divide the sum of bytes by 256
- round to nearest integer
multiply integer by 256
- origingal sum- product

Question 17

what is echo check

Answer 17

• a method of error detection where the receiving computer sends back an exact copy of the data to the sending computer.
• The sending computer then compares the data it originally sent to the data it has received back.
• If there is a match between the two data sets, then the transmission took place without error. If there is an error, the sending computer resends the data, and the process starts all over again.

Question 18

what is check digit

Answer 18

A check digit is an extra digit added to a number that is calculated from the existing digits in the number. It is used to check for errors during data entry.
eg: ISBN, barcodes

Question 19

what is automatic repeat request

Answer 19

• controls errors
• when data is recieved computer sends the aknowladgement which indicates weather data was sent correctly. can be positive or negative
• if negative computer will re request the data
• this process is repeated until tmeout is passed

Question 20

what is encryption

Answer 20

encryption scrambles data so it cant be understood without decoding it.

Question 21

wat are the 2 types of tect

Answer 21

plaint text- regular
cipher text- encrypted

Question 22

how does ceaser cypher work

Answer 22

shifts letter a number of positions to the right or to the left

Question 23

what is symetric encryption

Answer 23

a single key is used for encrypting messege and decrypting it. messege and key are send to reciever in seperate texts

Question 24

what is asymetric encryption

Answer 24

uses 2 keys, one private and one public- 1 for encryption and other is used for decryption.

Question 25

advantages of asymetric encryption

Answer 25

much more reliable- a messege cant be decrypted withput both keys