[aprssig] I-gates filtering on PID

spam8mybrain spam8mybrain at yahoo.com
Tue Oct 3 12:56:08 CDT 2017


By observation, I have noticed packets received over APRS-IS that contain the body
[ PID 77 ]
which I assume is some I-gate receiving an OpenTRAC packet. I don't think there's a way to remotely check the software version used to inject a packet into the APRS-IS network, except by checking all the Tier 2 servers until you find the injector's listing on a server status page. Anybody know a better way?.
Unfortunately, connected-mode AX.25 usually uses the same PID as APRS (PID F0,  or "no level 3 protocol"). What PID is FalconSat using? Whether an I-gate would forward packets that aren't UI frames would be an interesting experiment. They certainly forward PID F0 UI frames that are non-APRS old-style beacons.
I am tempted to run an experiment with my APRS software and see what it does. Any particular type of antenna needed to receive this satellite? Standard G5RUH modem encoding?
I can't speak for other software authors, but I routinely test my software with a full (unfiltered) APRS-IS feed to ensure it can handle the load (which only seems to be about 40 packets per second). With modern broadband, almost anyone should have the network bandwidth to handle that, let alone a tiny 9600-baud data rate.
Just my $.02.
Andrew, KA2DDOauthor of YAAC

-------- Original message --------
From: Kenneth Finnegan <kennethfinnegan2007 at gmail.com> 
Date: 10/3/17  12:39  (GMT-05:00) 
To: Robert Bruninga <bruninga at usna.edu> 
Cc: TAPR APRS Mailing List <aprssig at tapr.org> 
Subject: [aprssig] I-gates filtering on PID 

On Tue, Oct 3, 2017 at 6:41 AM, Robert Bruninga <bruninga at usna.edu> wrote:Since the BBS packets use a different PID I don't think you can see them through a normal IGate 
I was actually just discussing this with Hessu a few weeks ago as to whether this was a valid assumption or not. I know that at least in Aprx we don't perform any filtering based on PID. Should we be?
There has not been a clear mandate for I-gate software to filter on the PID, so I wouldn't be surprised if that feature is rare.
 and it would flood the APRS-IS..
So what? Any APRS-IS servers which have difficulty handling an additional 9600bps on their -IS stream have no business being an APRS-IS server. Worst case this thins the herd and we no longer have such an overkill of APRS-IS servers.
--
Kenneth Finnegan, W6KWF
http://blog.thelifeofkenneth.com/


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