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[aprssig] Why do routes go very wrong?

Lynn W. Deffenbaugh (Mr) ldeffenb at homeside.to
Fri Aug 13 12:58:39 UTC 2010


Fact number one about APRS-IS, messages are NOT routed at ALL!  The 
APRS-IS is simply a series of connections that deliver packets between 
connected clients.  Where those packets come from and what those clients 
do with received packets is up to the client, not the APRS-IS.

That stated, there is no way for any IGate to "pirate", "steal", or 
otherwise cause any other IGate to do anything in particular.

IGates operate on the packets that they received from the APRS-IS.  In 
most cases, if the message destination station was heard "recently" and 
"locally" to the IGate, it will wrap the message in a 3rd party wrapper 
and transmit it over RF.

I can't tell you what your IGate was doing, but the remote IGate 
probably heard a one of KE6SLS-7s packets and thought the station was 
close enough recently enough to gate the message to RF.  There is 
nothing malicious about this, it's just the way the loosely-coupled, 
non-coordinated APRS-IS network works.

To learn more about the magic of APRS messaging, check out my Wiki 
article at http://aprsisce.wikidot.com/aprs-messaging-explained

Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile and Win32

Jaye Inabnit ke6sls wrote:
> Hello all:
>
> My I-gate is ke6sls-3, my remote APRS unit is ke6sls-7.
>
> Tonight I did a little APRS-IS message to my APRS remote (using openAPRS).  
> Normally the test takes about 1 second, but not tonight.  Instead of APRS-IS 
> routing packets to my I-gate, they are being routing 110 miles north . .  My 
> I-gate only performs fill-in digi so none of the packets from the northern 
> station reach my remote.  I perform several more tests and after some time, 
> one packet makes it to MY I-gate from the APRS-IS server and is immediately 
> ack'd from my remote via my I-gate.
>
> I conduct several more tests only to find that again, APRS-IS is routing the 
> packets to the wrong gate.  Minutes later, one or two packets (out of many) 
> are routed to my I-gate and then immediately ack'd yet again.  I'm attaching 
> my rf-log so you can see what my server sees.  My server is responding 
> correctly to each of the packets received from either APRS-IS or RF.
>
> I'm completely stumped--it's like the northern station has somehow hijacked 
> routing--though that is plain silly, but still--why is this errornous routing 
> taking place?
>
> Then there is the question of why the station "n6nar" is involved in the digi 
> route.  I must be missing something obvious here but I'm sure I don't know 
> what that something is.
>
> What is happening here and what can I do to make sure routing is correct?
>
> Thank you, 73
>
>   
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