1.5.1 AL Description

Meters And More Application Layer is the part above Data Link Layer and below Meter/DCU Data Model in the Meters And More Stack, as seen on the figure.

Figure 1-18. APP Layer inside the Meters And More Layers model
Application Layer can be split in 2 different parts:
  1. Meter/DCU Application. Which handles all the Metering related data according to the Data Model used. This Application is implemented by the Meter/DCU manufacturer and is out of scope of this documentation.
  2. Modem Application (AL as defined in this document). Which manages duties related to PLC network, such as Network Management frames handling, and Encryption/Authentication of frames. This Layer is part of the Modem and thus is part of the provided Meters And More implementation.

Network Management

Meters And More protocol defines Network Management Commands to perform PLC related tasks, such as Network Discovery or Frame Counter maintenance an synchronization.

This Commands are managed directly by the AL at Meter side, so Meter Application does not need to take care of the PLC Network maintenance.

At DCU side this is handled differently. As DCU is the node that discovers and maintains the Network, according to policies and procedures that the DCU manufacturer may specify in different ways, the AL provides the API to perform this tasks, but does not perform them itself.

Encryption/Authentication

Meters And More defines the algorithms to use for Encryption and Authentication, but they are outside the Data Link Layer. This is why this Layer above DLL provides such algorithms so Meter/DCU can rely on this implementation.

The following algorithms are used, depending on used Command:
  • AES-ECB Encryption.
  • AES-CTR Encryption.
  • AES-CMAC Authentication.
Also depending on the Command, 2 different Keys are used:
  • Write Key.
  • Read Key.

The Frame Counter referred in the previous section, used in PLC frames (called LMON in the code), is also part of the Security suite included in the Modem.

Note: These Security parameters, Keys and LMON, have to be provided to AL by Meter/DCU Application. AL does not store any Security-related information.