Editing KNX (section)

== Kernel and message protocol ==
The common kernel sits on top of the physical layers and the medium-specific data link layer and is shared by all the devices on the KNX Network. It is OSI 7-layer model compliant:

* A general data link layer, which sits above the specific data link layers for each medium, provides access control and the logical link control;
* A network layer (for nodes with routing functionality) provides a segment-wise acknowledged telegram ([[Frame (networking)|frame]]) and controls the [[Hop (networking)|hop count]] of a frame;
* A transport layer enables four types of communication: one-to-many connectionless (multicast), one-to-all connectionless (broadcast), one-to-one connectionless, one-to-one connection-oriented;
* (OSI session and presentation layers are empty); and
* An application layer offers a toolkit of services to the application process.