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[aprssig] Digipeating behavior

Robert Bruninga bruninga at usna.edu
Sun Mar 12 13:45:15 UTC 2006

>>> scott at opentrac.org 03/12/06 12:16 AM >>>
>1. When first digipeater field ... with H = 0
>matches my callsign or alias:  Set H bit, retransmit frame.

No, only if it matches MYCALL.  If it matches any of the
UIDIGI Aliases, then do the above, but swap the digi field
with MYCALL. (callsign substitution).

>Bob suggests that this should not be limited to the first 
>H = 0 field.    Comments?

This should be an OPTION.  Called "pre-emptive" digipeating.
If it is enabled, then, yes, it will act on any match of H=0 and
then set it and all prior H bits.

>2. When digipeater field matches ALIASn-n, SSID is non-zero, 
>and payload+address is unique in past S seconds, decrement 
>SSID and set H = 1 if SSID is now zero.  
>Optionally insert MYCALL prior to ALIASn-n.

These days, the above Optional insert mycall, I think should
default to ON and only be a rare option that might be turned off.

>Should this apply only to the first H = 0 field?  Preemption 
>is also a possibility, where position is ignored, and all fields 
>up to the matching one get their H bits set.

Yes, this pre-emptive option (also rare) has some uses,
for exmaple when it is desired to gateway between
systems.  Day APPLE3-3,PEAR3-3 via a gateway into the
PEAR system.  The PEAR DIGI at the gateway point would
take over no matter the APPLEn-N.


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