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[aprssig] OpenAPRS has assumed "EMAIL" alias(was UniversalMessaging)

Pete Loveall AE5PL Lists hamlists at ametx.com
Fri Nov 7 19:53:58 UTC 2008


> -----Original Message-----
> From: Robert Bruninga
> Sent: Friday, November 07, 2008 12:35 PM
> Subject: Re: [aprssig] OpenAPRS has assumed "EMAIL" alias(was
> UniversalMessaging)
> 
> Many clients would not recognize this as an ACK because the
> SENDING callsign (WU2Z) did not match the outgoing callsign
> (EMAIL).  So, there were 3 possible fixes...:
> 
> 1) If the ACK was from WU2Z, then accept the ack
> 2) If the line number matched ANY outgoing message, then accept
> it?
> 3) Have WU2Z fake a "EMAIL>APRS::WB4APR...:ackline#"
> 
> I think we ended up loosening up the line-number match algorithm
> and adopted #2.  If #1 is hardcoded in any systems, then that is
> a problem.
> If the fix was #3, then that is a problem at the AX.25 level as
> Pete raises.  Pete, can you confirm that if the fix was #2, that
> then nothing in in the APRS-IS would care about a "message"
> addressee (though they do care about AX.25 addresses)?.

The fix was number 3 as that did not require any change to client software and did not cause any AX.25 issues.  EMAIL is a valid AX.25 callsign but, more importantly, it is a valid 3rd party callsign since it is never put on RF in an AX.25 header.  The APRS-IS clients and servers basically follow AX.25 addressing rules with the following additions:

Callsigns may be 3 to 9 characters.  If the callsign is longer than 6 characters, the total length of the callsign and SSID must be 9 characters or less.
SSID may be any one or 2 alphanumeric sequence (ASCII a-z, A-Z, and 0-9)
Callsigns may be upper and lower case

These extensions allow for more than 16 "stations" on APRS-IS and go with the understanding that gating to RF is in third-party APRS packet format.  It has been found that the Kenwood radios handle these callsigns just like object callsigns when they are in third-party packet format without problem.

73,

Pete Loveall AE5PL
pete at ae5pl dot net





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