Data Link Layer and Transport Layer

networking tcp data-link-layer
Utkarsh Srivastav picture Utkarsh Srivastav · Jun 7, 2012 · Viewed 18.3k times · Source

What is the need of error control at data link layer when Transport layer provides error control ? What is the difference between the two error controls ?

Answer

wroniasty picture wroniasty · Jun 7, 2012

Transport layer data could be broken down to many data-link layer frames/packets.

So it is possible that even without any data-link errors the transport layer stream/packet may be corrupt. Edit: This is because a transport layer path is usually composed of many data-link layer hops, for example:

Host1 <----> switch1 <----> switch2 <----> Host2

if a packet was lost between switch1 and switch2 then there would be no errors recorded on the switch2 Host2 link, but the corresponding transport layer stream would be corrupted.

On the other hand - once a data-link error is encountered it's possible to drop/restart the transport-layer transmission, without wasting resources.

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