[aprssig] Another advantage of SSn-N replacement for WIDEn-N

[Robert Bruninga]

Here is another advnatage of replacing WIDEn-N with SSn-N
as a UITRACE parameter in overloaded digis:

We used to have to begin a path with WIDE,WIDE2-2
for two reasons:

1) so that the first digi would do callsign substitution so that
we could indentify the source digi.  

2) so that if the first digi was  not WIDEn-N capable then
at least the station would get out.

Problem was that this caused extra copies to be generated 
by all surrounding  WIDE digis and propogated by n-N digis.

Under this new SSn-N paradigm, we want the universal
(non mobile path) to be SS2-2 (or so depending on local load)
without having to preceed it with a WIDE.  Here is how!

1)  Since SSn-N uses the digi's UITRACE parameter we 
automatically get the "first-digi" identificaiton.

2) We get these packets to the other LOCAL WIDE-only
hardware by Curt's suggestion of adding SS2-2 and SS2-1
to their UIDIGI list.

This is a  WIN*WIN since we no longer start with the dupe-
generating WIDE yet still the "WIDE" only digis will digipeat
it.  But the copies they generate GO NO FURTHER because
the SS2-2* or SS2-1* packet is used up.  Yet the original
SS2-2 that hits an n-N digi will go forward as they should.

Obviously if the ONLY digi that a user can hit is a WIDE-only,
then he must begin with WIDE or its call, but this use of
SS2-2 as the universal local path will see a lot less local
dupes... compared to WIDE,WIDE

Bob, Wb4APR