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[aprssig] More digis are changing to the new paradigm

Jason Winningham jdw at eng.uah.edu
Tue Jul 5 12:30:45 UTC 2005


Earl, I realize this doesn't help you to receive any stations, but in 
general NEWn-n does not prevent you from going out with a path of 
WIDE3-3,WIDE2-2 and still get 5 hops outbound, if you need it. (Is that 
true for digi_ned?)

I'm like Earl in that I don't particularly care about the Internet side 
of things.  If it weren't for severe weather messages and objects I 
don't think I would miss APRS-IS if it went away.  APRS is a radio 
thing for me.  I only state this because many many seem to assume that 
getting to an Igate is the only reason to TX an APRS packet, and for at 
least some of us this just is not true.

Going more than 2 hops is not "breaking the laws of physics".  There is 
no physical or mystical barrier at 2 hops on RF.  There is a 
mathematical formula that will tell you the probability of a packet 
successfully getting N number of hops, and it is based largely on the 
probability of a collision, which in turn depends greatly on the load 
on that particular network.  In may places, the chances of that third 
hop are slim to none due to the network load, but if the network is 
lightly loaded more than 2 hops is quite practical.

Since NSR was mentioned I'll comment on it, too. NSR is quite 
efficient, but it is statically configured.  All surrounding digis will 
require a manual reconfigure if a new digi goes online for any reason 
(new, temporary replacement, emergency or special event fill-in, etc).  
IMO, a statically configured network is just about as bad as a source 
routed network, albeit for entirely different reasons.  If digi owners 
are not well coordinated with _all_ digi owners around them _and_ quick 
to respond to changes requiring a configuration change, a static 
network _will_ break down.

I think for any next-generation APRS network, the "digis" should be 
smart enough to adapt to network load and allow packets to be repeated 
as many times as the load will allow, based on the users request.  Only 
then can we have a truly universal addressing scheme ("PATH") and a 
universal digi configuration.

-Jason
kg4wsv





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