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[aprssig] Premptive Digipeating

Matti Aarnio oh2mqk at sral.fi
Fri Nov 30 15:06:39 UTC 2012


On Fri, Nov 30, 2012 at 09:28:12AM -0500, Robert Bruninga wrote:
> 
> I cannot find previous threads on Premptive Digipeating.  So here goes.
> 
> PREMPTIVE DIGIPEATING DEFINITION:  When ON, the digi will search, starting
> at the first unused field to the end for a match to any of its potential
> matching aliases (MYCALL, MYALIAS, UIDIGI).  If a match, it will mark that
> and all prior fields as USED and will digipeat it once.

Naming it "preemptive" is somewhat misleading.
It does not preempt digipeater nodes that do not find themselves later in the path:

    SRC>DST,WIDE3-3,NODE2

That will do WIDE3-3 repeats all over the place, except that the NODE2 would
pick it up immediately even from first transmission.

Also explicit chains will do repeats all over the place:

   SRC>DST,NODE2,NODE3,NODE4

If the SRC is directly heard by NODE2 and NODE3, they both will transmit.
The retransmit by NODE2 may or may not be heard by NODE3, if it is heard,
duplicate filter should kick in.

Inserting WIDEs:

  SRC>DST,NODE2,WIDE1-1,NODE3,WIDE1-1,NODE4

Again directly heard by NODE2 and NODE3, packets sent out by them are different
and depending what other digipeaters hear, the first WIDE1-1 may get processed,
and the second WIDE1-1 will get processed anyway.


> Have I missed anything?
> 
> Bob, WB4APR
> 
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