The functions of service elements are described in a set of xml documents known as the USP data model. A data model describes how things like network interfaces, device functions, IoT objects, and more are exposed to controllers. You can find the USP data models at:
The current root USP data model is known as “Device:2”, otherwise known as TR-181. The earliest version of Device:2 that supports USP is Device:2.12.
On the USP data models web page, you can find several resources for the latest version of the data model.
In the full data model, you’ll see a list of the objects that comprise USP service elements. An object may be single instance, meaning that it is a static object of a service element. An object may also be multi-instance, which means that contains a table of objects of the same type. These objects are identified in the Agent’s instantiated data model with an instance identifier. Multi-instance objects may be creatable, or the table may be read-only.
Within each object you’ll find three types of elements: parameters, commands, and events.
The Device:2 data model outlines what Service Elements an agent can support. The set of objects and their elements that an Agent supports is referred to as its Supported Data Model, and can be retrieved via the GetSupportedDM message in USP. The set of objects and elements that are currently represented by the Agent - that is, the Agent’s state - is referred to as its Instantiated Data Model. Information about the Instantiated Data Model can be retrieved via the Get message and GetInstances message in USP.
The USP data model also contains a set of Profiles. Profiles can be used as a guideline for which objects and features to support, or can be used when building implementation requirements.
USP vs. CWMP Data Models USP draws from the same base for its objects and parameters as TR-069. USP has some minor differences in the way it handles commands and events, and includes those objects that are necessary for protocol operation. We go in-depth on how to understand the raw xml of CWMP/USP data model files in our videos on TR-069 data models.
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