Unique sensor identifier

Unique sensor identifier

I'm reviewing the Smart Room Sensor Technical Reference Manual, in particular the UP Payload Formats (Section 2). Section 2.1 (Frame Payload to Report Transducer Data) clearly describes the readings sent on LoWaRan port 10. 

A Sensor message payload can include multiple transducer data frames. The ordering of frames is not guaranteed (they can be in any order). A single payload may include data from any given transducer.

The frame payload description and examples are clear. My question is: How are the packets associated to specific sensors (transducers)? That is, how do you determine which sensor/transducer sent the payload? Is there some kind of header that needs to be stripped off and interrogated? Thank you.