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[aprssig] A few additional clarifications for APRS presentation, Please

Steve Noskowicz noskosteve at yahoo.com
Sun May 25 02:01:30 UTC 2008


  Thanks Steve & Tapio

Super!  My absorption rate has been rather good, dusty, but ok.  A few more
comments/clarifications...

> ...APxxxx stood for APrs UI frames ...

After posting (actually when I awoke this morning), I figured AP must come from
APRS.  Doh!

OK...the unproto parameter of Apxxx indeed is, in effect, an APRS super-group. 
 It's just that in APRS, everybody's "in the group".   Therefore, it's sort of
redundant (in an APRS only network). 




> > 3 – The actual "Path" in APRS is "determined by" the network...
> Actually not.  [snip]  no network intelligence in the sense of routing
tables, etc exists...

   Well, actually it is; as I *meant it* (note the quotes).  You describe
precisely my understanding of the RF network.  What I meant was that whatever
digis hear my packet and/or the digipeated version thereof  (up to the
originator's WIDEn-N limit) determine(s) where the packet "winds up".  This is
an ad-hoc determination – intended, yes, but not a specified, linear route as
in regular Packet.  Specific stations/locations are  not "built into" this
aspect of the APRS protocol.  Routing just happens....  However, it *does*
depend on where the digis happen to be and which happen to hear (remember, it's
RF) the packet (all within, of course, the WIDEn-N paradigm).   So, in that
sense, the RF net does determine the path(s) (that the packet gets routed
on/over).


> > 4 – APRS doesn't "connect". .. transmits and crosses its fingers
> Exactly! [...snip...] It's basically a kludge 

Well...I wouldn't class it as a Kluge.  Just a less sophisticated
protocol...with other disadvantages.


TWO you didn't comment on:
A---
   There are also  "Group Code" and "BNL (bulletin) Code" parameters.   If the 
 Unproto group is sort of an APRS Super Group then the others are sub groups,
within APRS?     Is this correct?    

Another thing I think I figured this out after posting is that the Apxxx
UNPROTO parameter is (a default) used for my *transmitted* packets while the
others are (filters) for receiving packets.  Right?  Of course I can send to
the other groups if I want.


B---  RE "Numbering" (~OT):
> >   I believe standard Packet packets are numbered since a message may
require
> > more than one packet.   Is this correct?  If not, what is the significance
of  Numbering the (regular type of) Packets.


Lastly, RE Tapio's:
> [snip] automated routing systems ... first connect to a node ...
> tell it the end node you want... it transparently relays ...

Oh yea...I read about this.  It's another variation on Packet, though a more
sophisticated one (layer).

Now, if I can just make the half-life of this knowledge longer than the time to
the presentation.  (:-)


-- 
73, Steve, K9DCI


      




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