[aprssig] Universal APRS messaging and authentication

[Robert Bruninga]

> It should be noted that www.openaprs.net 
> has had full messaging support for about 
> two months now.  Just signup for an account 
> (which is free)...

Greg, this is great news.  I think it is very important to have
that initial layer of authentication.  I have not used it yet,
but here are some additional issues which maybe you have
addressed:

1) Messages should be transmitted using the original APRS decay
algorithm to improve delivery reliability.  I'd suggest
something like Now, then 15
sec later, then 30, then 1 min, then 2, then 4 then 8 and then
stop.  

2) Such a system should have a line number so that it is acked.
And the application should watch out for the ACK.

3) Such a system should display to the browser sender when it is
acked or
when it has timed out.  It could also display the retry counter
and time-to -go, and time-to-die as an added bonus.

4) Somewhere in the message packet, the source of the Message
Engine should be identified.  There are two places.  One is for
anything going into the APRS-IS could use some kind of ID syntax
in the PATH like the Igates do now.  The other is in the
LINE-NUMBER.  I suggest the last two bytes for a unique
two-letter abreviation.  So the line number could be like this:
...{xxxID where "ID" is the engine sending the message.

Some radios only display the last two bytes of the line number
so that is a great place to show how the message was originated.
Of course, this obviates the use of REPLY ACKS, but that is a
small price to pay for the identification we gain.

Is there anything else we should require?

Thanks
Bob, Wb4APR