networking - Data Link Layer and Transport Layer -

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what need of error control @ data link layer when transport layer provides error control ? difference between 2 error controls ?

transport layer data broken down many data-link layer frames/packets.

so possible without data-link errors transport layer stream/packet may corrupt. edit: because transport layer path composed of many data-link layer hops, example:

host1 <----> switch1 <----> switch2 <----> host2

if packet lost between switch1 , switch2 there no errors recorded on switch2 host2 link, corresponding transport layer stream corrupted.

on other hand - once data-link error encountered it's possible drop/restart transport-layer transmission, without wasting resources.


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