[aprssig] what is RELAY, WIDE, TRACE, etc?
jdw at eng.uah.edu
Mon Aug 2 10:57:13 EDT 2004
I'm trying to figure out how the various addresses work with APRS. I
understand (and correct me if I'm wrong) that my station's call-ssid is
the AX.25 source address, the destination address is one of the generic
APRS destination addresses (typically identifying my rig), and the
digipeater addresses field is typically "RELAY,WIDE2-2" (or something
along those lines). These generic digipeater addresses may get
substituted or modified as they pass through digis.
Assuming I've got all that right, first question: what is the
difference between RELAY and WIDE? As far as I can tell from the
standpoint of an end user who is transmitting or receiving there is no
difference: RELAY,RELAY; RELAY,WIDE; WIDE,RELAY; WIDE,WIDE; and WIDE2-2
would all get me digipeated twice. I assume what various digipeaters
do with these may depend on what kind of digi it is and how it's
What's wrong with some sort of simple hop count/TTL? (Ignoring the fact
that it probably breaks the current system.) Wouldn't this allow digi
operators to easily reign in users who try to use 8 hops, as well as
shorten the overall packet length and reduce bandwidth?
Would it be better for the digipeater operator and not the user to
decide how many times a packet should get repeated, (e.g., default
"digipeater addresses" field is blank)?
How does TRACE fit into the picture, and how does it compare to WIDE?
Is there some documentation (book, URL, etc) that describes APRS
digipeating? Google gets me bits and pieces, but I can't find the
whole picture anywhere.
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