[Tinyos-help] tos2 message_t header

[João Paulo Amaro da Costa Luz Carneiro]

Hi all,
To explore the header of packets in tos2 I checked the CC2420.h
Can someone tell me what are the fcf and destpan fields?
Also, what is the dsn used for in the MAC level? Just for the acks or  
for anything else?
Regards,

Joao