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[aprssig] APRS talk in Los Alamos?

Tom Russo russo at bogodyn.org
Wed Aug 31 17:16:41 UTC 2011


On Wed, Aug 31, 2011 at 01:10:21PM -0400, we recorded a bogon-computron collision of the <bruninga at usna.edu> flavor, containing:
> Tom,
> 
> EXCELLENT explanation!  
> 
> Now would this problem go away if people used the WIDE2-2 path in that area
> instead of WIDE1-1,WIDE2-1??  I think so, because then the DUPE filter would
> work on the 2nd hop?

Yes, it would.

> If this fixes it, then our goal would be to get ALL such OLD KPC-3's to have
> a BEACON that says something like: "Use W2-2."  Especiall in an area whre
> most of the TNC's have this problem?

The recommendation to use W2-2 is in fact on the web page of the club that
maintains the digis (www.urfmsi.org).  I agree that it would be a good idea 
for those digis to have some kind of standard beacon that would be 
easily recognized by users.  What format and means do you suggest?  I could 
possibly pass it on to the fellow who maintains the digis.  It might be some 
time, though, before it gets implemented.

> -----Original Message-----
> From: aprssig-bounces at tapr.org [mailto:aprssig-bounces at tapr.org] On Behalf
> Of Tom Russo
> Sent: Tuesday, August 30, 2011 8:18 PM
> To: TAPR APRS Mailing List
> Subject: Re: [aprssig] APRS talk in Los Alamos?
> 
> On Tue, Aug 30, 2011 at 05:05:25PM -0600, we recorded a bogon-computron
> collision of the <ws5n at wildblue.net> flavor, containing:
> > <html><head><meta name="Generator" content="PSI HTML/CSS Generator"/>
> 
> [you might want to adjust your mail program to send only plain text email to
> APRSSIG --- those of us using old-fashioned text mail programs get to see
> all the HTML markup, which I've hand-edited out in my reply]
> 
> >While there I hope you can monitor the APRS traffic around the city.
> &#160;When I drive in to Albuquerque, I start hearing "MY POS" repeats
> sometimes three or four times each time I beacon. &#160;I have heard it as
> much as 7 times! &#160;I am running WIDE1-1,WIDE2-1 in the mobile. &#160;I
> have my suspicions as to what is happening, but I don't have the expertise
> to analyze the situation and make recommendations. &#160;I'd love to hear
> your take on it, if you see the same behavior.
> 
> That's because all the nearby digis are ancient KPC-3 TNCs with old
> firmware,
> with broken handling of WIDEn-N:  they fail to mark the final hop as used,
> so if WIDEn-N were implemented normally the path you are using would only
> be a one-hop path:
> 
>    first transmit:  WIDE1-1,WIDE2-1
>    First digipeat:  LAMOSC*,WIDE1,WIDE2-1
>    First digipeat(2):  SANDIA*,WIDE1,WIDE2-1
>    First digipeat(3):  CAPILA*,WIDE1,WIDE2-1
>    First digipeat(4):  ELKMTN*,WIDE1,WIDE2-1
>     (etc. for every digi that happens to hear you)
>    End of line, because nobody will digipeat this (WIDE1 is showing as the
>     first unused digi, and nobody will do anything with that).
> 
> SO, the work-around is that all of these digis have a workaround in place:
> MYALIAS is set to WIDE1-1, with all the problems that go with it ---
> notably,
> no dupe checking on the first hop.  So you get THIS mess instead:
> 
>    first transmit:  WIDE1-1,WIDE2-1
>    First hop:  LAMOSC*,WIDE2-1
>    First hop(2):  SANDIA*,WIDE2-1
>    First hop(3):  CAPILA*,WIDE2-1
>    First hop(4):  ELKMTN*,,WIDE2-1
> and then
>    Second hop:   LAMOSC*,SANDIA*,WIDE2
>    Second hop:   LAMOSC*,CAPILA*,WIDE2
>    Second hop:   LAMOSC*,ELKMTN*,WIDE2
>    Second hop:   SANDIA*,LAMOSC*,WIDE2
>    Second hop:   SANDIA*,CAPILA*,WIDE2
>    Second hop:   SANDIA*,ELKMTN*,WIDE2
>    and so on and so on.
> 
> 
> That is, if you use WIDE1-1 you're no better than the Bad Old Days of
> RELAY,WIDE, thanks to outdated hardware with outdated firmware.
> 
> The KPC-3's are all donated hardware from WA5IHL who used to maintain a
> large
> number of normal packet nodes with them, and repurposed them in the early
> days of APRS.  It is not reasonable to expect that they'll all be replaced
> in any sort of short order with more modern hardware/firmware, so we're
> stuck
> with the local advice NOT to use WIDE1-1,WIDE2-1 in the central New Mexico
> area --- just use WIDE2-2 so that all dupe checking is actually done
> properly.
> With WIDE2-2, no ping-ponging is possible, you get fewer "MY POS" beeps
> on your D7X0, and the channel gets less congestion.

-- 
Tom Russo    KM5VY   SAR502   DM64ux          http://www.swcp.com/~russo/
Tijeras, NM  QRPL#1592 K2#398  SOC#236        http://kevan.org/brain.cgi?DDTNM
 "One man alone can be pretty dumb sometimes, but for real bona fide
 stupidity, there ain't nothin' can beat teamwork." - Edward Abbey




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