Reassembling Zigbee received packet


I’m actually looking for a method in C++ reassembling packets effectively.
In other words, I would like to find a way to manage packets I receive from the Xbee PRO S2B in API mode connected to my Arduino.

The problem is I noticed the frame ID field used in Transmit packet request are not present in the Zigbee Receive Packet frame and the output is not parsed (I receive two frame even if ID is 01 and 02 respectively).

So is it normal?

Thanks in advance!