[aprssig] IGate Registering for ANSRVR (Messaging failures)

Pete Loveall AE5PL Lists hamlists at ametx.com
Fri Jul 15 14:15:26 EDT 2016

No, it is how networking works!  I will give you two specific examples that shows how a RO IGate can break messaging.

#1 is Anthony's example.  The RO IGate gates his HT's message packet (let's say it is a messaging capable HT) but a bidirectional packet does not because it never gets digipeated.  The remote station sees his packet but the remote station's ack and possible responses are not seen since no bidirectional IGate considers his HT as local.

#2 is a little more obscure but just as important since it is much harder to isolate.  Bidirectional IGate (let's call it RW) is connected to a server (connection type is irrelevant for this connection). That server (let's call it RW's server since it is often times either integral or in the same location as the RW IGate) is connected to APRS-IS via a restricted feed ("filter" is an inaccurate word; the feed is "restricted" to packets for the connected station and any stations the connected station has recently gated to APRS-IS plus any packets defined in a filter if defined).  Before you say it can't be or that is bad design, that is how most home installations of javAPRSSrvr are configured as they are on restricted bandwidth connections.  There are others who also run in this type of configuration.  Now, let's use the example in #1 but say the RW IGate does see that packet after one hop.  But the RO IGate already got the packet through APRS-IS to RW's server so dupe elimination prevents RW's server from sending the RW-received packet upstream.  Therefore, the upstream server to RW never sees the packet that RW gated to its server.

Now you might claim close-coupling of the software in #2 could force RW's server to send the packet anyway regardless of dupes but that is a bit self-defeating for other reasons and does not resolve the issue when the IGate is completely separate software from the server.

I am not assigning "fault" to anyone or anything.  I am pointing out how RO IGates can and do interfere with APRS messaging.  I am also pointing out how this can be very difficult to track down with the denial of such cases (and these are only 2 examples).


Pete Loveall AE5PL
pete at ae5pl dot net

> -----Original Message-----
> From: Steve Dimse via aprssig
> Sent: Friday, July 15, 2016 12:57 PM
> To: TAPR APRS Mailing List <aprssig at tapr.org>
> Subject: Re: [aprssig] IGate Registering for ANSRVR (Messaging failures)
> > On Jul 15, 2016, at 1:48 PM, Pete Loveall AE5PL Lists via aprssig
> <aprssig at tapr.org> wrote:
> >
> > is better than a receive-only IGate which can interfere with the proper
> operation of an IGate not receiving a full feed (the majority).
> You need to explain this, I don't see how it is possible. But even if it is I'd argue
> the problem is not the one-way IGate. which has been part of the APRS IS long
> before filtering was! If there is something you are filtering out of the feed for
> an IGate that interferes with its proper function, isn't it the filter's fault, not the
> one way IGate's fault?
> Steve K4HG

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