The protocol levels, error checking methods, and topologies
so for the protocol levels try and memorise the communication systems framework,
for the error checking methods:
PARITY BIT - Worst because it can only detect 1 other possibility which means that it can only detect 50% of the errors of corrupted messages
CHECKSUM - Average because it can detect a larger amount of errors but some data can still slip through if the digits which are added still equal the same sum and provide the same remainder.
CRC - Best it can detect 99.9% errors because it uses a complex division process by combining all the numbers into one large number instead of adding then dividing it by the divisor, which gives a insanely large remainder which is almost not likely to occur if any data changes.
Topologies:
Memorises the shapes of them
Star - best, can still work if one connection is broken, most expensive to set up
Bus - Worst, data collides all the time slowing the transmission down, doesn't work if the main line is broken, cheapest
Ring - Alright, data still collides sometimes but rarely, doesn't work if ring is broken, medium price
Wireless - Alright, useful for any wireless medium such as phones, medium price
Hybrid - Mixture of any topology to create a better more functional one, can be expensive or cheap based on topologies used.
Hope this information helps, if you need anything else let me know.
