Data transmission - Topic 2 Flashcards
What is the structure of a data packet? [3]
Header
Payload
Trailer
What is the structure of a header? [4]
IP address of source device
IP address of destination device
Sequence number of the packet (reasembly instructions)
size of the packet in bytes
What is the structue of a payload?
Actual data 64KiB
What is the structure of a trailer? [3]
Method of identifying the end of the packet
error checking method (CRC)
what is CRC
method of error checking
How is CRC done? [4]
-sender adds up all the 1 bits in the payload and stores it as hex in the trailer
-receiver recalculatesd the number of 1 bits in the payload
-computer checks this value against the one sent
-if good, no error, if bad, packet is resent
Explain packet switching [3]
each packet is sent independently
nodes containing routers determine the route of the packet (repeated until destination is reached)
-takes in consideration of busy ness of the route
benefits of packet switching [4]
-don’t need to tie up a single communication line
-can re-route
-easy to expand package usage
-high data transmission rate
drawbacks of packet switching [3]
-packets lost
-prone to erros for streaming
-delay of packets
What is serial data transmission [2]
data is sent one bit at a time
over a single wire/channel
What is parallel data transmission [2]
several bits of data are sent
over several channels/wires at the same time
benefits of serial data transmission [3]
-less risk of external interference
-more reliable transmission over long distance
-less expensive
benefits and drawbacks of parallel data transmission [2]
-faster rate of data transmission
-data can arrive unsynchronised
What are the 3 methods of data transmission?
simplex, half-duplex, full-duplex
