[aprssig] Error checking within APRS packets

Jason KG4WSV kg4wsv at gmail.com
Mon Jun 20 14:47:07 EDT 2011

On Mon, Jun 20, 2011 at 1:38 PM, Gregg Wonderly <gregg at wonderly.org> wrote:
> Do we have any real examples of how the quiet TX 1/2 through packet followed
> by loud TX complete packet can result in a "packet" too long that would
> corrupt internal TNC buffers?
> Will the start of the "loud" packet result in an end of packet recognition
> of the "quiet TX" packet.

I am not convinced this can happen.  AX.25 includes a frame delimiter.
 In order for this scenario to occur, the second packet's start frame
delimiter couldn't be present at the TNC, else it would simply signal
the (premature) end if the first interrupted packet to the TNC.  Once
this vanishingly unlikely event happens, then the checksum would have
to coincidentally match.

I haven't done the math, but my guess is you're more likely to be
struck by lightning than see this occur on VHF.


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