[aprssig] Ideal Digipeater Behavior

Jason KG4WSV kg4wsv at gmail.com
Thu Aug 25 09:42:21 CDT 2016


On Wed, Aug 24, 2016 at 7:41 PM, Kenneth Finnegan <
kennethfinnegan2007 at gmail.com> wrote:


> * The two places where the preempt RR bit is documented disagree with each
> other. I think RR-bits.txt is correct.
> http://www.aprs.org/aprs12/preemptive-digipeating.txt
> http://www.aprs.org/aprs12/RR-bits.txt
>

IMO all this is ridiculous. At best it will be partially implemented and
the results will be useless.  Just like existing attempts at route tracing
are at best unreliable, because there is no standard implementation and
much of the OTA infrastructure is built on prehistoric hardware that won't
get changed.


> * How should we be punishing excessively long paths
>

you DON'T punish. You don't drop a packet out of spite.  If you find
yourself using word like "punish", your next move will _not_ be a good
network design decision.

Feel free to fix/truncate/rewrite it to the locally acceptable maximum hop
count path.

Think about an IP TTL.  It will probably leave your system at 255, but the
first router it passes through may drop it to 127 (I think I've seen that
particular scenario). It most certainly would not be configured to drop the
packet.



>
> * When would we ever not want preemptive digipeating?
>


when we get a real layer 3 network instead of this inconsistent patchwork
of hacks? And creating such a thing would, IMO, be _easier_ than dealing
with the hacks.


[rant for a real APRS network deleted.  check the archives, i'm sure i've
made it more than once.]

-Jason
kg4wsv
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