MAC or IP Layer Traffic ?

From the network analyser, we find that on the MAC Layer, there is a lot of
traffic from Host A to Host B (Host A is the File Server and Host B is a
Database Server).

On the other hand, from the IP Layer Conversation analysis, we find that
most of the traffic is from Host B to Host A.

We would like to know is it not uncommon and what constitutes the MAC Layer
traffic ?

Thanks