simulating network association


I have two modules xbee s2c, I use them as FFD and RFD. I’m developping a fuzzing module via python. The first stap is to simulate an association request. I have follow the folowing steps
1 generate my association request to the coordinator
2 listen to the network
- when i listen , i can sea my association request
- sometimes i also see it’s answer
3 i send data request to the coordinator
4 listen to the network
- when i listen, sometimes i see the ack relate to my data request
- i never see the association response.

My questions are
1 why sometimes i have an answer, and sometimes no answer?
2 why i never have the association response packet.

My environment is based on gnu radio/scapy radio



What XBee product are you working with and what firmware versions on that radio?