[aprssig] Packet routing, path specification.

AE5PL Lists HamLists at ametx.com
Thu Jun 23 05:16:52 CDT 2005

You are exactly right, Wes.  More importantly, a LAN in DC will be
significantly different than the one in Baltimore, yet they overlap.
This is the nature of RF, let alone the NSR algorithm.  The people in DC
don't necessarily want to see the activity in Baltimore nor vice versa.
Yet people in the suburbs in-between will be seen in both _while_ they
are in-between the cities.  It may be that local coverage "cells"
(digipeaters) may only show up in one or the other, but that is also the
nature of a LAN.  While someone in Baltimore might want to see someone
in DC, the person in Baltimore can cause this to happen by messaging the
person in DC (discussed in another thread).
Whether you intended it with APRS or not, it is a broadcast protocol
(not point-to-point) and as such, it should be expected to reach the
area local to the station and no further.  As messaging is the only
point-to-point mechanism in the protocol, that has been accounted for in
the gateway architecture.  BTW, the backbone does not have to be the
Internet.  Germany uses an RF backbone very effectively, for instance.
There can be a mix of RF and Internet, that is inconsequential.  The key
is to keeping the low bandwidth broadcast packets as local as possible
to the transmitting station with a minimum of knowledge required by the

As you have so aptly pointed out, the general user base is not going to
know (or even have access to) the topology of the network.  Just like
when you turn on your computer and connect to the Internet, the user
should not need to know anything more than transmitting on a particular
frequency (equivalent to dialing in or connecting via broadband) for
their packets to be heard _locally_, and to be heard world-wide via the
broadband backbone.

I think you will find, after careful consideration, that the NSR
algorithm really does work in your area as well as throughout the rest
of the world.


Pete Loveall AE5PL
mailto:pete at ae5pl.net 


	From: Wes Johnston
	Posted At: Wednesday, June 22, 2005 9:00 PM
	Subject: Re: [aprssig] Packet routing, path specification.
	You see, it's not a rigid boundary lan.  (I get the feeling you
may think it is).  It can be.... but it can also be a smooth hand off
from one overlapping coverage area to the next.  I used big cities in my
example for everyone's sake.. I expect this model to be downsized to
actually fit the aloha circle of a given area, realizing that the
boundaries may actually be towns with names like Mayberry MD, and
Whistlestop VA instead of Philly, DC and NYC.

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