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[aprssig] Re: Tracker Smart Pathing

Jason Winningham jdw at eng.uah.edu
Thu Mar 23 11:59:08 UTC 2006


On Mar 22, 2006, at 7:13 PM, Wes Johnston wrote:

> Note that no matter what my path is, people very close to me hear  
> my packet.

I really think that, for most people and applications, the practical  
definition of "very close" will turn out to be "useless".

> Hey, a way to limit mobile's sending the same position while parked  
> all day is to use the dupe checker with an extended timer... like  
> 255 seconds.
[snick]
> The problem with this is that the digi doesn't know the difference  
> between a static position and an aprs client sending a message and  
> retrying.

That's why just twiddling parameters on UIDIGI will _never_ result in  
a smart digipeater.  Most digis on the air (KPC3, TNC-2, etc) are  
Commodore 64 era microcontrollers.  Today you can get a flash based  
microcontroller with more horsepower than that old C64 and _way_ more  
processing power than the digi's microcontroller for $3 or $4.

> I'm just not sure that the job of decoding the multitude of aprs  
> packet types and deciding yea or nay can or should be done at the  
> digipeater level. Isn't this why we have a 7 layer OSI model?

Depends on who you mean by "we".  APRS users only have 3 of those  
layers - physical, data link, and application.

Having said that, the smart digi could also operate at the APRS  
application level and do lots of things for us.

> However it would be handy if the digi used to stop redundant parked  
> car packets was smart enough to not stop message type packets...  
> but now I get into a moral delima.

Why?  There is no moral dilemma to dropping packets of the joker who  
forgot to turn off his $GPGGA spewing TNC when he parked.  Let one  
through every 5 or 10 or 15 minutes (tunable based on network load,  
maybe station type?).  A digi that's going to be smart enough to drop  
"redundant" position reports _must_, IMO, be smart enough to let  
message traffic pass normally.

-Jason
kg4wsv







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