[aprssig] APRS Message Callsign SPEC- Ambiguity (ACKS still work)

Lynn W. Deffenbaugh (Mr) ldeffenb at homeside.to
Tue Apr 26 20:48:58 CDT 2016


APRSISCE/32 expects and requires the ack to come from the addressed 
station.  It will not accept an ack from another source station even if 
the proper ack sequence is provided.  There was actually a bug in one of 
the early iPhone (or was it Android) APRS client applications that 
caused it to send an ack to the last station a message was received 
from, but for EVERY message it saw after that.  APRSISCE/32 calls that a 
"pirated" ack and ignores it.

I cannot think of a single reason that an ack from a non-addressed 
station should satisfy a message addressed to a specific station.

Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile and Win32



On 4/26/2016 5:35 PM, Robert Bruninga via aprssig wrote:
>
> Hummh…..
>
> This is true. If somehow my client thinks its name is “WB4APRlid” and 
> it sees an APRS message to “WB4APRlid” (from anyone), then it will 
> send an ACK from whatever my TNC callsign happens to be to whatever 
> the sender’s TNC call happened to be.  And the format of the ACK does 
> not involve the “WB4APRlid”  at all. The ACK still works.
>
> Or am I missing something?
>
> Bob, WB4aPR
>
> *From:*aprssig [mailto:aprssig-bounces at tapr.org 
> <mailto:aprssig-bounces at tapr.org>] *On Behalf Of *spam8mybrain via aprssig
> *Sent:* Tuesday, April 26, 2016 2:36 PM
> *To:* Lynn W. Deffenbaugh (Mr); TAPR APRS Mailing List
> *Subject:* Re: [aprssig] APRS Message Callsign SPEC- Ambiguity
>
> One interesting point here is that RF stations wouldn't have to ack 
> messages from this mixed-case service; the mixed-case service will 
> have to ack messages from the RF ground station. So that's not an issue.
>
> The issue here is whether any given ground client can send to a 
> mixed-case addressee.
>
> Andrew, KA2DDO
>
> author of YAAC
>
>
>
> -------- Original message --------
> From: "Lynn W. Deffenbaugh (Mr) via aprssig" <aprssig at tapr.org 
> <mailto:aprssig at tapr.org>>
> Date: 04/25/2016 9:56 PM (GMT-05:00)
> To: TAPR APRS Mailing List <aprssig at tapr.org <mailto:aprssig at tapr.org>>
> Subject: Re: [aprssig] APRS Message Callsign SPEC- Ambiguity
>
> Yaesu APRS radios will not ack a message if it comes from an -SSID 
> that is not -0 (suppressed) through -15 even though the APRS protocol 
> for messages is always in the payload portion for 3rd party packets 
> gated from the APRS-IS to RF with the ack coming back.
>
> APRSISCE/32 upcases APRS message targets.  At least I think it does 
> but I didn't check the source code just now.
>
> Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile and Win32
>
> On 4/25/2016 5:07 PM, Robert Bruninga via aprssig wrote:
>
>     There is an unintended ambiguity in the APRS SPEC regarding the
>     addressee in the APRS MESSAGE format.
>
>     It was intended that the TOCALL of any transmitted message could
>     be sent to ANY 9 character callsign field and this included
>     mixed-case.  Although TNC’s have historically forced callsigns to
>     UPEPRCASE only, this is only a limitation of TNC’s and was not
>     intended to be a limitation of APRS.
>
>     STATION names, OBJECT names, ITEM names were intended to be a
>     general 9 character mixed case field in APRS padded to 9 with spaces.
>
>     We just noticed that some radios do not allow sending an APRS
>     message to a mixed case address.
>
>     Unfortunately, the QIKCOM-2 satellite which does DTMF-to-Voice and
>     APRS-to-voice has a special message address of “QIKCOMsay” for all
>     messages it is expected to speak.  So some people will not be able
>     to exercise this text-to-voice messaging capability.
>
>     I wont make this mistake in any future satellite, but we are stuck
>     with it.
>
>     SO, we might ought-to-identify all APRS radios and APRS clients
>     that have this uppercase-only restriction on MESSAGE Callsigns.
>
>     I can say the Kenwoods have it.  Others?
>
>     See http://aprs.org/aprs11.html and specifically, see:
>
>     See http://aprs.org/aprs11/aprs-names-and-spaces.txt
>
>     Bob, WB4APR
>
>
>
>
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>
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