[aprssig] Premptive Digipeating

[PE1RDW]

On Fri, 30 Nov 2012 15:28:12 +0100, Robert Bruninga <bruninga at usna.edu>  
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.
>
> PACKETS TO HOME SCENARIO:  In this scenario your goal is to get your
> packets targeted to a particular digi or area.  The path WIDE2-2,HOMEX
> With the HOMEX digipeater recognizing pre-emptive digipeating would make
> sure that all your packets got to HOMEX in from 1 to 3 hops.  To get them
> say 4 hops from City A to City B without flooding everywhere, the path
> WIDE1-1,CITYA,WIDE2-1,CITYB would get to CITYB no matter where you are in
> A or B or inbetween, but not involve ANY OTHER DIGI's than the shortest
> path between them.  ETC...
>
> Or CITYD,CITYC,CITYB,CITYA would let you go on a trip to CItyD, but your
> packets would get back home to A no matter where you were inbetween.   
> When
> close, then they would only go 1 hop.  Or if you wanted those at CityD to
> anticipate your arrival, you might use the path CITYA,CITYB,CITYC,CITYD
> and then your packets would all preceed you to CITYD until you got there,
> but with fewer and fewer hops as you got close.
>
> GATEWAY SCENARIO:  IN this scenario there is a special event on FREQB  
> with
> lots of FREQB digis that desires to get at least one (and only 1) copy of
> each packet into the 144.39 system via a cross-channel gateway with the
> callsign GATE.  The path of FREQB7-7,GATE,WIDE2-1 would make sure that a
> packet got everywhere in the special event network but only one copy
> always gets through the gateway at least one hop into the APRS network.
> (such as the linear appalachan trail event or an underground multihop  
> cave
> event...
>
> NO PREMPTIVE DIGIPEATING ON UIFLOOD and UITRACE.  The reason is, that it
> would preclude any use of any kind of WIDEn-N AFTER going through a gate,
> and that is one of the main reasons for doing it.
>
> Remember, these 4 hop Premptive SPECIFIC paths are MUCH less load on the
> network than a WIDE4-4 which can potentially cause 34 DUPES, compared to
> only a maximum of 4 hops with the explicit preemptive hop approach.
>
> Have I missed anything?
>
> Bob, WB4APR
>
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That is pretty much how I see it working right now in digined so looks  
about right.

-- 
73 Andre PE1RDW