lower level; lower layer
Computing term referring to a lower level in a hierarchy, such as network layers, software architecture, or data structures.
In the OSI reference model, the lower layers handle physical communication.
This protocol detects errors in the lower layer.
階層 is a general term for 'hierarchy' or 'layer', while 下位層 specifically refers to a lower level within a hierarchy.
Compound of 下位 (lower rank) and 層 (layer).