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[aprssig] Reminder about Callsign-SSID's on APRS-IS

AE5PL Lists HamLists at ametx.com
Tue Mar 1 01:41:51 UTC 2005

APRS-IS is one big network comprised of the Internet and all the
attached RF networks.  As such, it is important that callsign-SSID
combinations (AE5PL is a SSID of zero, AE5PL-15 is a SSID of 15) are
unique between all clients that will show up on APRS-IS.  This is one
reason why it is allowed, per the APRS spec and Bob's recent statements,
to have non-AX.25 compliant SSID's on APRS-IS.  This gives you more than
16 combinations for multiple clients on RF and on the Internet.  Do to
AX.25 limitations, you are restricted to 0 through 15 for RF clients but
you can use anything including characters on APRS-IS.  It has been
demonstrated that non-numeric SSID's gated to RF are compatible with RF
clients including the Kenwood radios.

javAPRSSrvr (most core and tier2 servers) looks at the callsign
following the q construct and if it finds the callsign of a verified
login there but that login is on a different connection, the packet is
dropped as a looped packet (a packet carrying a verified login in the q
construct coming in from a different connection is assumed to be a
looped packet).

If you look at the packets "missing" from the different core server data
streams, most of them can be attributed to duplicate callsign-SSID
logins from different software on different servers.

If you are running multiple APRS clients/servers, on RF and/or on
APRS-IS, please take a moment to ensure that you are using unique
SSID's.  The SSID has no effect on login passwords.  One that we see
quite often is a weather station application using the same SSID as a
standard APRS client.

Just want to see as many packets as possible get through.


Pete Loveall AE5PL
mailto:pete at ae5pl.net 

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