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[aprssig] Packet routing, path specification.

Robert Bruninga bruninga at usna.edu
Thu Jun 23 14:27:44 UTC 2005


>>> HamLists at ametx.com 06/23/05 6:16 AM >>>
>APRS ... 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. 

APRS was intended as a BROADCAST PROTOCOL for
ROUTINE operations just to let everyone know
who was on the air and avaiable for participation.
It retains FULL POINT-to-POINT capability by users
who understand what a PATH is...  It was intended
to let SENDERS direct their packets on a non-routine
basis anywhere they needed to accomplish the
comunications need AT HAND.

>...the general user base is not going to know 
>(or even have access to) the topology of the network.

And that is simply beacuse of fast-to-market
APRS clones that overlooked all the APRS fundamental
features that were intended to display  that topology 
to the end user so that he could SEE the path needed
to accomplish the objective needed in real time.
1) Every station on the air (except Mobiles and WX)
    has a PHG range that is supposed to show its 
    reliable RF range circle so that any path between
    overlapping circles can be used for fast efficient
   exchange of data.
2) The most popular reecnt program a) did not even
    display PHG circles to the users, b) does not even
    provide the mechanism for them to enter PHG for
   their own station.

The result is exaclty what you say,  Users of that 
software are clueless about paths because they
cannot directly see the toploogy on their maps!

Displaying the network topology was fundamental to
APRS so that no one would be cluless and could
direct their packets where they needed to go for
the task at hand.     Network Topology was all part 
of the prptocol, just ignored in some software, leading
to a mass of users who are blind to the topology.

>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 

Comparing a 1200 baud channel to the infinite bandwidth
of the internet is apples and oranges.

>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.

It all depends on what you mean by "work".
I absolutely agree,  It will guarnatee improved
"local" operation but at the same time completely
prohibit any choice by the end user as to where 
he needs his packets to go in response to an
immediate non-routine need other than what the
local SYSOP defined as "local".

This is a great network design, but it undeermines
the inherent ad-hoc flexibility intended in the
general purpose APRS digipeater system for
response to real-time emergent needs.

Bob





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