PathOverkill

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Path Overkill

A path that specifies more hops than necessary for the area you're operating in can be considered an abusive path. An example of a path that's excessive or abusive almost everywhere is "WIDE1-1,WIDE3-3." This path can result in up to four "hops" - that is, it can be repeated up to four times. In virtually any area with APRS coverage, this is too much.

One of the things about the APRS Internet System (APRS-IS) is that the same packet can get to the Internet by many routes, and the APRS-IS system keeps only one of them. The one it keeps is basically random - it keeps one of the many copies that arrive, and throws away the rest. While experimenting with high-hop-count paths one night, the copy that survived was one that had gone through the full four hops, and the results show exactly why this is abusive.

Example: The route part of the packet on when viewed as "raw packets" might look like this: WR6ABD,N6CP-1,WA6LDQ-3,WA6YLB-3*,WIDE3,qAo,KF6HJO

That means it had been digipeated by WR6ABD, N6CP-1, WA6LDQ-3, and WA6YLB-3 before finally being heard by the IGate KF6HJO. After looking up the locations of the digis and IGates, I created a map image of the hops it took. This one packet traveled about four hundred miles!

This does not mean the four-hop route was justified. The exact same data also got to APRS-IS in a single hop, because there is an IGate that can hear WR6ABD, the first digipeater this packet hit. And there are certainly other routes that this same data took to get to the Internet, too; this is just the one copy that survived. The point is that a path whose hop count is too high can "light up" a wide geographic area unnecessarily, using up time on the one APRS frequency and interfering with other APRS users hundreds of miles away.

The best advice is to use a path that specifies only as many hops as you need for the way you use APRS and the area where you are using it.

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