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[aprssig] Packet routing, path specification.

Rick Green rtg at aapsc.com
Wed Jun 22 16:58:13 UTC 2005


WIth all this talk of digipeater paths, ALOHA circles, network congestion, 
and 'new paradigms', I find myself ever more confused.
   I keep coming back to the desire that the network manage itself, and 
minimize or eliminate the need for the end-user to know the topology of 
the network in the neighborhood they just happen to be passing thru.
   I keep coming back to the following concept:

   A digipeater sysop manages local traffic by defining their own service 
area, and refuses to digipeat any packets originating outside that service 
area, no matter what the path specification.

   Out of this basic concept, we get only three possible path 
specifications:

   a)  No VIA.  Local point-to-point coverage only.  Great for high-density 
special events like Dayton, Aeronautical mobiles, etc.  Will be gated to 
APRS-IS if heard by an IGate.

   b)  VIA APRS.  Means 'digi me as far as congestion allows'.  The digi 
looks at the position in the packet and will digi if it's in the current 
service area.  Will be gated to APRS-IS if heard by an IGate. (if the 
'already digipeated' bit is on, perform dup-checking before 
digipeating again.)

   c)  VIA XXyy.  WHere XXyy is a Maidenhead grid square.  Digis will treat 
this like VIA APRS, and IGates will gate this back to RF only if XXyy is 
within their service area.  Since the object position itself is 'remote', 
such packets will not be further digipeated once gated back to RF.

   This third option allows for Bob's special needs, taking advantage of 
the APRS-IS as a 'tunnel'.  The Cadets at the academy can watch the 
football, even if the RF network is saturated that weekend, and the sysops 
have shrunken their service areas accordingly.  His Mother can watch his 
progress to Thanksgiving dinner.  Long-haul truckers could also 'direct' 
their packets back to home, etc.  And congested areas in between wouldn't 
have to suffer from the additional traffic...

-- 
Rick Green

"They that can give up essential liberty to obtain a little
  temporary safety, deserve neither liberty nor safety."
                                   -Benjamin Franklin




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