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[aprssig] Aprx v2 beta, now with Viscous Digipeater

Matti Aarnio oh2mqk at sral.fi
Thu Oct 22 09:56:52 UTC 2009


Hi,

Knowing that people are sceptical on things they have not tried, I did
some comparisons on what happens when a fill-in system is digipeating
like any normal WIDEn-N system would, and when it has a bit of viscousness
on that digipeating.

The results are visible on this article, in particular its graphics:

  http://wiki.ham.fi/Viscous_APRS_Digipeater


The bottom graph is number packets sent (per 10 minutes) by that node.
At first with normal delayless digipeat, and then with 5 seconds of
viscousness configured in.


Really an excellent reducer of transmissions for systems considered
to be in a "fill in" role.

The system has also tons of built-in default behaviours documented
elsewhere, like limiting the total number of requested and completed
hops to 4 each.  One can freely put in a request like:

     OH2XYZ>APRS,WIDE2-2,WIDE2-2,WIDE2-2

Which most exiting systems see no evil.
This one says: "req=6, done=0.  requests are over my limit, drop it."

Also if the New-N-request is written like:  WIDE3-6,   this one considers
it bogus, and drops it.

Also, when this sees bogus UIDIGI output of  WIDE3  without H-bit,
this one sets the H-bit and checks the next field for possible trace/wide
operation.  If there is no next field, no digipeat is done.

This one sits on amazingly small Linux capable devices and environments,
like NSLU2, OpenWRT, etc.  Putting it on a uClinux has not been tried
as of yet.

Further links:
  http://wiki.ham.fi/Aprx.en
  http://ham.zmailer.org/oh2mqk/aprx/


73 de Matti, OH2MQK



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