Re: [Duplicate telemetry sequence, Delayed or out-of-order packet (sequence number)]

James Ewen


I kind of thought the data spoke for itself. 

It looks to me that NC4HC-15 has a hand in delaying the packets in question. 

I have not gone into detail looking at the delays between packets though. The KPC-3 issue tends to be an accumulating delay over time, so you will see a fairly consistent delay from the offending station. The delay is out the communications port, not with packets that are handled internally, hence the usual problem being at an i-gate. 

A KPC-3 acting internally as a digipeater doesn’t get affected by the communications port delay, and usually does not exhibit this behaviour. 

A way that you can cause issues with a digipeater is having it set up with hold off in an over saturated area. This means the digipeater can sit for a long time waiting for a break to be able to forward the packets it has stored. 

APRS is designed with some very specific implementation requirements, and most people setting up APRS, and APRS infrastructure rarely understand these requirements. 

Putting a digipeater on the highest point around where it can hear for hundreds of miles is detrimental to the APRS network in the area when there are other nearby digipeaters. 

Bob’s design for APRS is to have digipeaters purposefully cause packet collisions to kill propagation. If one installs a digipeater up high where it can rarely hear a quiet channel, and has hold-off enabled, the digipeater can end up waiting politely for a clear channel. This can then cause random delays once the digipeater finally gets a chance to spit out its packets. 

Again, listening to the RF channel will let you actually see what is happening in the area. 

The APRS-IS stream will not easily show you what is happening on RF. 

On Tue, Nov 23, 2021 at 12:16 Rick <kd4dra@...> wrote:
James I have been looking at the RAW in the decoded format and I find A lot of Out of Sequence and the most common digi is the NC4HC-15
if that digi is not involved then the packets proceed as they should, I see it working with the other stations, as you did.
So I think I just keep trying to get this owner to do the right thing, I really don't know who the trustee is for the Machine.
I'm pretty sure I'm right. What say you.

On Tue, Nov 23, 2021 at 1:04 PM James Ewen <ve6srv@...> wrote:

I got off my phone and onto a computer with a bigger screen... I see you copied packets from three different stations, although one didn't have any dupes highlighted.

Let's walk through this... here's a packet marked as a dupe. I'm going to select the payload `n5|n,au/]"7;}= and search for another instance of this. I find it 1:07 earlier in the log.

2021-11-23 06:25:36 MST: KO4HKX-9>S4US6U,WIDE1-1,WIDE2-1,qAR,GSPSC:`n5|n,au/]"7;}=
2021-11-23 06:26:43 MST: KO4HKX-9>S4US6U,GSPSC,NC4HC-15,WIDE2*,qAR,KR4NO-1:`n5|n,au/]"7;}= [Duplicate position packet]

Let's continue that, just to narrow it down to just the packets that are delayed and their original packets.

2021-11-23 06:52:45 MST: KO4HKX-9>S4US2R,WIDE1-1,WIDE2-1,qAR,GSPSC:`n5qn+<u/]"78}=
2021-11-23 06:53:31 MST: KO4HKX-9>S4US2R,GSPSC,NC4HC-15,WIDE2*,qAR,KR4NO-1:`n5qn+<u/]"78}= [Duplicate position packet]
2021-11-23 07:23:19 MST: KO4HKX-9>S4US1X,WIDE1-1,WIDE2-1,qAR,GSPSC:`n5fl <0x1c>u/]"7I}=
2021-11-23 07:24:06 MST: KO4HKX-9>S4US1X,GSPSC,NC4HC-15,WIDE2*,qAR,KR4NO-1:`n5fl <0x1c>u/]"7I}= [Duplicate position packet]
2021-11-23 08:19:57 MST: KO4HKX-9>S4UR7W,WIDE1-1,WIDE2-1,qAR,GSPSC:`n4?l <0x1c>u/]"7:}=
2021-11-23 08:20:28 MST: KO4HKX-9>S4UR7U,WIDE1-1,WIDE2-1,qAR,GSPSC:`n4;lI=u/]"74}=
2021-11-23 08:20:36 MST: KO4HKX-9>S4UR7W,GSPSC,NC4HC-15,WIDE2*,qAR,KR4NO-1:`n4?l <0x1c>u/]"7:}= [Duplicate position packet]
2021-11-23 08:20:59 MST: KO4HKX-9>S4UR7S,WIDE1-1,WIDE2-1,qAR,GSPSC:`n47mqgu/]"79}=
2021-11-23 08:21:16 MST: KO4HKX-9>S4UR7U,GSPSC,NC4HC-15,WIDE2*,qAR,KR4NO-1:`n4;lI=u/]"74}= [Duplicate position packet]
2021-11-23 08:21:39 MST: KO4HKX-9>S4UR4W,WIDE1-1,WIDE2-1,qAR,GSPSC:`n47mT2u/]"78}=
2021-11-23 08:21:40 MST: KO4HKX-9>S4UR7S,GSPSC*,NC4HC-15*,WIDE2*,qAR,KO4CEF-1:`n47mqgu/]"79}= [Rate limited (< 5 sec)]
2021-11-23 08:22:09 MST: KO4HKX-9>S4UR3V,WIDE1-1,WIDE2-1,qAR,GSPSC:`n4=mqlu/]"75}=
2021-11-23 08:22:18 MST: KO4HKX-9>S4UR4W,GSPSC,NC4HC-15,WIDE2*,qAR,KI4M-1:`n47mT2u/]"78}= [Duplicate position packet]
2021-11-23 08:22:41 MST: KO4HKX-9>S4UR2U,WIDE1-1,WIDE2-1,qAR,GSPSC:`n4<lq u/]"77}=
2021-11-23 08:22:44 MST: KO4HKX-9>S4UR3V,GSPSC*,NC4HC-15*,WIDE2*,qAR,KO4CEF-1:`n4=mqlu/]"75}= [Rate limited (< 5 sec)]

I have highlighted the common stations in the duplicated packets. KR4NO-1 gated a bunch, but we also see KO4CEF-1 and KI4M-1 gate the packets, so we focus on GSPSC and NC4HC-15 as a common element in all packets.

2021-11-19 18:59:41 MST: KO4NNH-1>STSX3S,WIDE1-1,WIDE2-1,qAR,GSPSC:`n7Ul p>/`"6Q}Fred in mobile_1
2021-11-19 19:00:56 MST: KO4NNH-1>STSX3S,GSPSC,NC4HC-15,WIDE2*,qAR,GSPSC:`n7Ul p>/`"6Q}Fred in mobile_1 [Duplicate position packet]
2021-11-22 19:17:44 MST: KO4NNH-1>STTS7X,qAR,GSPSC:`n3=lK4>/`"7+}Fred in mobile_1
2021-11-22 19:18:40 MST: KO4NNH-1>STTS7X,NC4HC-15,WIDE1*,qAR,KR4NO-1:`n3<l 7>/`"7+}Fred in mobile_1 [Duplicate position packet]

This narrows things down as the second dupe only has NC4HC-15 in the "has been digipeated" list, but we can also see that some unreported digipeater handled the packet by the missing WIDE2-1 element. We know the original packet was asking for 2 hops, and one is missing in this packet.

2021-11-23 08:24:07 EST: KD4KBO-2>ST4T2V,WIDE1-1,WIDE2-1,qAR,KD4DRA-1:`n+qo@Wk\'|!1&9|!wlc!|3
2021-11-23 08:24:53 EST: KD4KBO-2>ST4T2V,GSPSC,NC4HC-15,WIDE2*,qAR,KR4NO-1:`n+qo@Wk\'|!1&9|!wlc!|3 [Duplicate telemetry sequence, Delayed or out-of-order packet (sequence number)]
2021-11-23 08:27:46 EST: KD4KBO-2>ST4V4X,WIDE1-1,WIDE2-1,qAR,GSPSC:`n.8pJyk\'|!5&<|!w!G!|3
2021-11-23 08:29:06 EST: KD4KBO-2>ST4V4X,GSPSC,NC4HC-15,WIDE2*,qAR,SHOJCT:`n.8pJyk\'|!5&<|!w!G!|3 [Duplicate telemetry sequence, Delayed or out-of-order packet (sequence number)]
2021-11-23 08:29:43 EST: KD4KBO-2>ST4V7S,WIDE1-1,WIDE2-1,qAR,GSPSC:`n.Vm}<k\'|!6%p|!w'W!|3
2021-11-23 08:30:40 EST: KD4KBO-2>ST4V7S,GSPSC,NC4HC-15,WIDE2*,qAR,KI4M-1:`n.Vm}<k\'|!6%p|!w'W!|3 [Duplicate telemetry sequence, Delayed or out-of-order packet (sequence number)]
2021-11-23 08:33:16 EST: KD4KBO-2>ST4X1W,WIDE1-1,WIDE2-1,qAR,GSPSC:`n/(n#<0x1d>k\'|!8%D|!wG;!|3
2021-11-23 08:33:55 EST: KD4KBO-2>ST4X1W,GSPSC,NC4HC-15,WIDE2*,qAR,KR4NO-1:`n/(n#<0x1d>k\'|!8%D|!wG;!|3 [Duplicate telemetry sequence, Delayed or out-of-order packet (sequence number)]
2021-11-23 08:39:43 EST: KD4KBO-2>ST4Y7V,WIDE1-1,WIDE2-1,qAR,GSPSC:`n0pnKAk\'|!:%D|!w4#!|3
2021-11-23 08:40:36 EST: KD4KBO-2>ST4Y7V,GSPSC,NC4HC-15,WIDE2*,qAR,KR4NO-1:`n0pnKAk\'|!:%D|!w4#!|3 [Duplicate telemetry sequence, Delayed or out-of-order packet (sequence number)]
2021-11-23 09:03:22 EST: KD4KBO-2>ST5P0S,WIDE1-1,WIDE2-1,qAR,GSPSC:`n0Tm,Rk\'|!$%f|!ww{!|3
2021-11-23 09:03:38 EST: KD4KBO-2>ST5P0R,WIDE1-1,WIDE2-1,qAR,GSPSC:`n0VlRjk\'|!&%Y|!w:&!|3
2021-11-23 09:03:55 EST: KD4KBO-2>ST5P0S,GSPSC,NC4HC-15,WIDE2*,qAR,KR4NO-1:`n0Tm,Rk\'|!$%f|!ww{!|3 [Duplicate telemetry sequence, Delayed or out-of-order packet (sequence number)]
2021-11-23 09:04:41 EST: KD4KBO-2>ST5P0R,GSPSC,NC4HC-15,WIDE2*,qAR,KR4NO-1:`n0VlRjk\'|!&%Y|!w:&!|3 [Duplicate telemetry sequence, Delayed or out-of-order packet (sequence number)]

This station again shows both GSPSC and NC4HC-15 handling the packets.

Digging around for a while, I found another station.

2021-11-22 10:05:31 MST: KF1SH-9>S5SR4X,CHMBRS,NC4HC-15,WIDE2*,qAR,SHOJCT:`nLb!7)k/]"<h}Monitoring 146.520=
2021-11-22 10:05:43 MST: KF1SH-9>S5SS3T,CHMBRS,CLINCH,WIDE2*,qAO,KI4HDU-3:`nM^!@kk/]"<m}Monitoring 146.520= [Location changes too fast (adaptive limit)]
2021-11-23 08:42:42 MST: KF1SH-9>S5SR0U,KM4BLG-15*,WIDE1*,WIDE2-1,qAR,WT4R-1:`n@&nRUk/]";D}Monitoring 146.520=
2021-11-23 08:42:44 MST: KF1SH-9>S5SQ9R,NC4HC-15,WIDE1*,WIDE2-1,qAR,SHOJCT:`n@:n\/k/]";A}Monitoring 146.520= [Rate limited (< 5 sec)]
2021-11-23 09:06:33 MST: KF1SH-9>S5SW0Q,WIDE1-1,WIDE2-1,qAR,ANDMTN:`n*[ pOk/]"<(}Monitoring 146.520=
2021-11-23 09:07:28 MST: KF1SH-9>S5SW0Q,WIDE1,NC4HC-15,WIDE2*,qAR,KR4NO-1:`n*[ pOk/]"<(}Monitoring 146.520= [Duplicate position packet]

The location changes too fast is not a duplicate, but rather packets being seen close together in time, with large distance changes. This can be due to a delayed packet that hasn't been seen before showing up late.

Similar issue with a rate limit, the delayed packet and a live packet end up too close in time, and the rate limit algorithm triggers.

With these errors, you have to be a bit more of a sleuth, and look for other evidence of who the culprit was. Without the duplicate packet knowledge we have from above, it would be harder to find the offender. BTW, the KF1SH-9 also have another station that is delaying packets. I ran across it while trying to find examples for this email. Add that to your list of things that are broken.

So, based on the above, do you see any common callsign? 

Hessu filters out these "bad" packets to make the maps on his website look nicer. It gets rid of the zig-zag/backstitch issues that you can see when delayed or out of order packets are plotted on a map. While it makes the map look nicer, it hides the issue, and lets people live with their heads buried in the sand. Rather than fix the root cause, he implements a work around to hide the problems. Obviously one guy in Scandinavia can't fix all the problems around the APRS infrastructure, but hiding the problem doesn't help.




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