Meters And More Data Link Layer is the part above PHY Layer and below Application Layer in the
Meters And More Stack, as seen on the figure.
Figure 1-8. Data Link Layer inside the Meters
And More Layers model
It contains 2 different blocks, according to different functionalities: LLC and MAC.
LLC
LLC sub-layer interfaces the Upper Layers on the upper side and the MAC sub-layer on
the lower side.
It operates end-to-end between master nodes and all the slave nodes. Offers a
connectionless-type service to equipment applications, according to the exchange
procedure required.Figure 1-9. LLC End to End Communication
LLC sub-layer does not check the correctness of the used communication parameters;
it’s up to the upper layer to select them properly.
MAC
In this sub-layer, the repetition functionalities are distinguished from the physical
interfacing functionalities.
Repetition:
Operates end-to-end between master node and all the network slave nodes
offering a connectionless service.
Uses the services supplied by Physical Layer to transfer frames between a
master node and a slave final node on a multi-point Data-Link with hidden
stations (slave nodes that need one or more repeaters to communicate with
the master node). See figure above, on LLC section.
Manages the timers of busy network condition in the repeaters.
Physical Interfacing:
Frames encapsulation.
Received frames filtering, on the basis of a single or grouped address.
Frame errors detection.
Connection electric phase detection of Low Voltage Line.
