[aprssig] APRS-IS Duplicate Packets

[Pete Loveall AE5PL Lists]

The servers are properly eliminating dupes.  Unfortunately, the packets you presented are not dupes.  Upon closer inspection (on jfindu.net's ListPackets.aspx page), the packets gated to APRS-IS by N4XI-11 and WB9TLH-15 contain trailing spaces while packets from the other IGates do not contain those trailing spaces.  If your packets contain trailing whitespace, this can occur by IGates or the server(s) they are connected to improperly trimming packets of data content (there is some attempt by javAPRSSrvr to reduce these duplicates, but if the trimmed packet shows up first, as in this case, there is not much that can be done).  If your packets do not contain trailing white space, then these IGates are improperly appending the white space.

In my experience of monitoring APRS-IS traffic, the most common occurrence is when the packet contains trailing whitespace and some software or device in the path (either on air or on APRS-IS) is improperly modifying packet content by trimming the whitespace.

73,

Pete Loveall AE5PL
pete at ae5pl dot net

> -----Original Message-----
> From: Max Harper
> Sent: Monday, May 03, 2010 1:29 AM
> 
> I have noticed for some time now that the APRS-IS is not filtering out
> all
> duplicate packets. I currently have a filter that only sends me packets

> KG4PID-15>APN391,NV4B-7*,WIDE2-1,qAR,KB4YTM-
> 1:@030210z3417.45N/08742.32W_000/000
> g000t069r000p157P157h97b10081.DsVP
> KG4PID-15>APN391,NV4B-7,WD4INS-4,WIDE2*,qAR,WB9TLH-
> 15:@030210z3417.45N/08742.32W
> _000/000g000t069r000p157P157h97b10081.DsVP

> KG4PID-15>BEACON,SPKSCH*,WIDE2-2,qAR,N8DEU-5:>Digi / Weather
> kg4pid at yahoo.com
> KG4PID-15>BEACON,NV4B-7,WIDE1,WAVTN*,WIDE2-1,qAR,N4XI-11:>Digi /
> Weather kg4pid@
> yahoo.com