[aprssig] WIDEn-N question My Summary

Robert Bruninga bruninga at usna.edu
Wed Nov 4 18:35:45 EST 2009

> Though this is "recommended" for mobile 3-hop :
> Is not, the "theoretically" correct 3 hop path:
WIDE1-1,WIDE3-2  ?

No, that violates APRS reecommendations.  It wouild arrive with
ambiguity as to what was the senders intent...  It is
indistinguishible from  something like WIDE1-1,WIDE3-3 when it
arrives and so it simply is not receommended.  EVERY path should
be entered such that "n" and "N" are EQUAL.  That is the APRS
standard, and that is what everyone expects.  There is no reason
to play with the little "n" or you violate common expectations
and make the network indeterministic.

Now, having said that..  There is ONE EXCEPTION.  And it is the
use of WIDE2-1 as an alternate means for indicating ONE HOP but
without having to use WIDE1-1.  Because WIDE1-1 is "special" and
we do NOT want to use WIDE1-1 in some cases and so we had to
invent the WIDE2-1 SPECIAL CASE to allow this to happen.
> The "3" indicating the Original Packet's desire for a 3 hop
*total* ?

No, the only exception to having "n" EQUAL to "N" is WIDE2-1.
Nothing else should violate this rule.

Hope that helps


> Reasoning: Since the 2-hop is:  WIDE1-1,WIDE2-1
>    and the "2" indicates a *total* desire for a 2-hop ... it 
> 'seems' resonable that the "3" should be there for the 3-hop
> { of course, we know that a 2-hop can't be the alternative 
> "WIDE1-1,WIDE1-1", so therein lies the rub. ]
> At the risk of over explaining my rationale...
> [ I view this second path segment (...WIDE2-1) to be 
> "prematurely decremented" by the originating station.  It 
> "seems" to have originally requested 2 *more* hops, but it 
> only requested one with the "-1".  This is part of the basis 
> for my saying the "3" is "correct" in the other one.  
> We had an email exchange a while back and this was my 
> departing understanding.  You also added that, due to 
> history, folks in some areas would find the "3-2" confusing 
> and therefore to just use the "2-2"  anyway.  
>  So is/was the original intent for each segment of the path 
> descriptor to use the "n" to specify only its OWN sub-max-hop 
> number,  OR was the  *last*  path descriptor to show the 
> Packets TOTAL max-hop number.  I see several conflicting 
> issues for either concept to work 100%.
> Sorry, I've been an Engineer too long.
> As I said, I don't go to this detail in any beginner talks I 
> gave/will give.
> -- 73, Steve, K9DCI
>   http://k9dci.home.comcast.net/
> --- Robert Bruninga, in part, wrote:
> > I can not make sense out of all the back and forths here. 
> > here is  what it should be:
> > 
> > Mobiles: 
> > For one hop:  Use WIDE1-1 
> > For two hops: Use WIDE1-1,WIDE2-1 (Higher reliability using 
> fill-ins)
> > For two hops: Use WIDE2-2     (Slightly more efficient)
> > For 3 hops:   Use WIDE1-1,WIDE2-2 BUT NOT RECOMMENDED IN
> > 

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