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[aprssig] AX.25 RR bit test - Holy Grail?

Steve Dimse steve at dimse.com
Fri Nov 30 19:24:22 UTC 2012


On Nov 30, 2012, at 2:10 PM, Heikki Hannikainen wrote:

> On Fri, 30 Nov 2012, Jason KG4WSV wrote:
> 
>> IMO, it's a mistake to shove layer 3+ data into layer 2 (data link) fields, both for specific reasons
>> like Andrew points out, and just on general principle.
> 
> Second that. It would be *wrong* to do that, and it would not work with existing software some of which would either ignore the bits (loosing information), or ignore the packets having those set (even worse).
> 
> Also, there is no construct in the APRS-IS packet format to embed the values of those bits in the APRS-IS stream.

I'm not a purist about layers, it is debatable that this is really level 3, and things are already so messed up in APRS I would not stand on principle if it was otherwise a good idea. Nor would I be worried about APRS IS compatibility. APRS-IS is completely unsuited for any sort of propagation study. If I had thought how about the temptation to use it would be irresistible for some people who do not understand "bad data is worse than no data" I would have had IGates strip out all the path info when I designed the APRS-IS! So I'd actually be in favor of anything that helped people realize the path data is worthless.

But to me the death knoll is compatibility. There are just too many devices for this to ever be proven not to be harmful. 

Bob, I urge you to withdraw this part of the proposal immediately.

Steve K4HG


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