topic 2 - communication and internet tech Flashcards
data transmission types (5)
- simplex
- duplex
- half-duplex
- full-duplex
- serial
- parallel
simplex
data transmitted one way only
duplex
data transmitted in both way
half-duplex
data transmitted in both ways but not at the same time
full-duplex
data transmitted in both ways at the same time
serial(2)
- one bit sent at a time over a single wire (eg. computer to printer)
- used to send data externally between devices
parallel (2)
- multiple bits sent at the same time using multiple wires
- used to send data internally
why use serial instead of parallel when connecting device to PC
- single wire reduces the cost
- single wire means less chance of corruption
- more reliable over time
bits still synchronised after transmission
asynchronous transmission (2)
- Data is sent in form of byte or character
- time interval of transmission is random
synchronous transmission (2)
- Data is sent in form of blocks or frames
- time interval of transmission is constant
USB (7)
- universal serial bus
- data transmission method
- uses serial transmission
- device automatically detected
- only fits one way; it cant fit incorrectly
- industry-standard
- backwards-incompatible
methods of error-checking (4)
- parity check
- checksum
- ARQ; automatic repeat request
- check digit
how does parity check work (5)
- checks byte of data
- a parity bit is added
- counts num of 1s
- can be odd or even
- if parity incorrect, error is detected
when will parity check not work (2)
- multiple errors in same byte
- ## 2 bits interchanged
how does ARQ (automatic repeat request) work (6)
- uses acknowledgement
- check performed on receiving data
- if error detected request sent to respond data
- resend request repeated until data sent correctly
- send an acknowledgement that data is received
- if acknowledgement not received in set time data is resent
checksum (4)
- values calculated from the data
- it is transmitted with the data
- value recalculated after transmission
- values compared after transmission to check for error
what is an IP address
location of a device on a network
what is a MAC address
number that uniquely identifies a device
what does https
hypertext transfer protocol secure
describe what browsers do (3)
- interprets HTML
- URL entered into browser
HTTP protocol used
requesting web pages
- request
- web browser used
- url entered into browser
- http protocol used - sent
- url contains domain name
- domain name used to locate IP address
- DNS server stores index of IP address and domain names
- web browser sends request to web server - received
- data stored on wbeserver
- web server sends data to browser
- browser translate html
