Chapter 2 : Communication and internet technologies Flashcards
What is Simplex data transmission? And give an example
It is where data is transferred only one way (This is Unidirectional) (Radio)
What is Half-Duplex data transmission? And give an example
It is where data is able to be transferred both ways but can only go one way at a time (This is Bidirectional) (Walkie Talkie)
What is Full Duplex data transmission? And give an example
It is where data is able to be transferred both ways at the same time (This is Bidirectional) (Phone call)
What is Serial data transmission?
It is where data is sent over a single wire, 1 bit at a time (can be Simplex, Half-Duplex or Full Duplex)
Where is Serial data transmission used and why?
It is used over long distances as there isn’t a problem with data arriving out of synchronisation
What is Parallel data transmission?
It is where data is sent as several bits of data over several wires where each wire is used to send a bit
Where is Parallel data transmission used and why?
It is used over short distances as it is very fast but it isn’t used over long distances as the bits can become skewed and unsynchronised
What is Asynchronous data transmission?
Is when data is transmitted in an agreed bit pattern and are sent with control bits to mark out the groups of data
Advantages and Disadvantages of Asynchronous data transmission
A. You don’t need the computers to be in sync
D. Bits are wasted as control bits
What is Synchronous data transmission?
Is when data is transmitted in a continuous stream with timing signals so that both computers are in sync
Advantages and Disadvantages of Synchronous data transmission
A. It is faster
A. Doesn’t need control bits
D. It needs the computers to be in Sync
What does USB stand for?
Universal Serial Bus
What kind of data transmission does USB use (Asynchronous or Synchronous)?
Asynchronous
How does a computer know if a USB device has been plugged in?
A small change in the voltage level on the data signal wires in the cable
What does a computer do if it doesn’t recognise a device?
The computer will look for the driver which matches the device and if this is not available then it will prompt the user to download it
What are the advantages of USB?
- Devices plugged into the computer are automatically detected and the device drivers are automatically uploaded
- The connectors can only fit one way, this prevents incorrect connections being made
- It is industry standard so there is a lot of support for it
- Multiple different data transmission rates are supported
- Newer standards are backward compatable
What are the disadvantages of USB?
- The maximum cable length is currently 5 meters
- The current transmission rate is less than 500 megabits per second
- The older USB standard may not be supported in the future
Why use Error-Checking methods?
When data is transferred it can be corrupted or changed so it makes sure that the data hasn’t had this happen to it
What are the 4 methods of error checking?
- Parity Checking
- Automatic repeat request (ARQ)
- Checksum
- Echo Checking
How does Parity checking work?
It adds an extra bit to a byte and counts the number of 1s in the byte and if its odd and they are using even parity it would be a 0 in the extra bit
How many dimensions can Parity checking work?
As many as the dimensions of the data that is sent
What does ARQ stand for?
Automatic Repeat Request
What is an Acknowledgement when used in an ARQ check?
A message that is sent by the receiver indicating that the data has been received correctly
What is a Timeout when used in an ARQ check?
The time allowed to elapse before an acknowledgement is received
How does the the sender know if the data has been sent correctly using ARQ?
If the acknowledgement isn’t send back to the sender before timeout occurs then it knows it wasn’t
How is a checksum preformed?
It is calculated by the sender and sent as an additional byte, then the receiver will calculate the checksum and compare it with the one sent, if they are not the same then the receiver will ask for it to be sent again
How does echo checking work?
The sender send the data to the receiver and the receiver sends the data back so the sender can compare the data,
What is the main disadvantage of echo checking?
If the data was changed on the way back the sender will not know
What is the internet?
A world-wide system of computer networks and computers. All computers attached to the internet can communicate with each other providing a number of rules and protocols are adhered to.
What is an ISP?
Internet Service Provider
What does IP address stand for?
Internet Protocol address
What is an IP address?
A unique 32-bit number given to each device that is connected to the internet
What does MAC address stand for?
Media Access Control address
