PDUs as Analogous to API Endpoints

Each PDU in SMPP serves a role similar to a REST API endpoint. As we mentioned before, SMPP uses binary PDUs to make operations.
A PDU consists of two main parts:
SMPP Header. The SMPP header is a fixed 16-byte structure present in every SMPP message. Contains metadata for processing the PDU. Fields include command length, command ID, command status, and sequence number.
SMPP Body (Optional, Depends on PDU Type). Some PDUs require a body, while others (like unbind) do not. PDUs like submit_sm include destination address, source address, and message content.
Optional fields (TLVs - Tag-Length-Value) allow for additional parameters like validity period, DLR requests, etc.
Each SMPP PDU follows this general structure:

Let's have a more detailed look at this construction: