[Tinyos Core WG] CC1000 Header

[David Moss]

David -

In the meeting this morning I brought up a concern about 
the CC1000 header not containing a DSN byte like the 
802.15.4 CC2420 packets.  I'd like to get your input on 
this to see if this is something we can include in the 
CC1000 stack.

The argument for having a DSN byte in the CC1000 packet 
header is we can more easily detect and reject duplicate 
packets.  This is especially important for the version of 
low power listening that sends shorter packets redundantly 
from within the radio stack.  As you know, the transmitter 
in this low power listening implementation is able to quit 
early by detecting an ack from a receiver; however, the 
receive needs some kind of filter to reject duplicate 
packets coming from the transmitter.  Another instance 
where the DSN byte is useful is when a message transport 
layer retransmits a single packet from within the radio 
stack for some duration of time, attempting a reliable 
delivery.  Set the DSN byte on transmit at the top of the 
stack, check it on receive at the bottom.

One of the questions that arises as part of adding a DSN 
byte to the packet header is how should the AMPacket 
interface be modified to access this byte?  And, should 
the equivalent functionality that a DSN byte provides be a 
requirement for all radios in TinyOS?

It's possible that this update should happen as part of a 
cc1000_lpl asynchronous/synchronous lpl stack release like 
I have access to locally, but it's good to start thinking 
about it now for compatibility.

-David Moss