[aprssig] Why Not "Gate in Vicinity"

[Georg Lukas]

Hello Pete, hello list,

* Pete Loveall AE5PL Lists <hamlists at ametx.com> [2011-12-26]:
> You can text more reliably with your cell phone than using APRS and
> you can use many free locator services if you desire. It is not the
> responsibility of the individual amateur radio operators to
> accommodate misconfigured cell phone users by making their IGates
> unreliable for amateur radio use.

I do not understand the panic about abuse of APRS-IS by non-HAMs. Of the
by now almost 5000 passcode requests issued via the APRSdroid request
form, there was around a dozen with non-callsigns, and I tend to
attribute at least half of these to people who made an error in filling
out the form, whereas the other half probably was by actual non-HAMs.

As you wrote yourself, there are better free geolocation services out
there. Why should anyone in their right mind try to use APRS(IS)
instead?

> Any throttling as you describe on a network that has no network level
> protocol by definition makes it unreliable. APRS-IS is amateur radio,
> not public Internet or cell phone services.

APRS is unreliable by definition. Why should APRS-IS be more reliable in
that regard? There are already retransmissions defined as part of the
protocol for the really critical things (messaging).

> Regarding "appropriate" beacon rate, what is an appropriate rate on
> RF?  That is your measuring stick.

You can not define a one-rate-fits-all limit. Where I live, the total
APRS activity is around one packet every five minutes. Even if there was
some misconfigured client flooding the medium, I would be glad to see
some activity... :-P

Of course we should agree on a sane default which makes reverse-igating
usable even in crowded areas and which does not require a ph.d. to
adapt. IMHO, the best suggestion so far was a per-callsign(*) limit for
reverse-igating of maybe 1 pkt/minute, with a burst limit of e.g.
4/minute (I have seen APRS-RF rigs with a 15 second corner pegging
setting, so this seems sane to me).

(*): I would further suggest to have two limits per callsign:
messages should have their own rate limit as opposed to posits,
objects, weather reports etc, which can go together.

> Again, this is amateur radio and because there is no way to throttle
> what is passed through APRS-IS without breaking its underlying
> premise, it cannot be assumed that the amateur radio operators must
> alter their operation just to accommodate non-amateur radio equipment.

But it is very well possible to throttle what is going from IS to RF on
an igate without breaking anything.

> The focus should not be "how to gate everyone to RF" but how to
> provide for the primary purpose of APRS-IS: support amateur radio
> communications.

I'm in full agreement to this statement. It was my main motivation for
developing APRSdroid and I have not given up on it since. An APRS-IS
application on your cellphone gives you many advantages when mobile or
portable: it frees up the second band on your dual-bander or allows to
participate in APRS without spending >500$ for the gear.

However, as it is now, APRS-IS stations have second class value because
their positions are mostly not forwarded to RF at all and their messages
get through with luck only. We as a community need to decide what way
should be followed: should APRS-IS be kept a one-way street with no
reverse igating at all, or should it become a full class citizen
allowing 100% interaction between RF and IS?

In the latter case, we need additional mechanisms to prevent flooding of
RF by misconfigured software, as the responsibility for the RF
transmissions is with the iGate operators. However, this problem is
solvable in the iGate software.

> But if you have "passcodes for everyone" as pushed by some recent
> authors, you have third-party messaging occurring which also puts in
> jeopardy the entire premise of APRS-IS.

The APRS-IS passcode algorithm is well-documented for years and can be
applied by anyone with half an hour of time and access to Google. So
far, the doom of APRS-IS due to third-party messaging failed to appear.
I am very positive that this will not change with the existence of
smartphone APRS apps, as there are better alternatives out there for
non-HAMs.

> Unfortunately, to change either the underlying network protocol,
> authentication, etc. will immediately disenfranchise thousands of hams
> using clients that cannot be updated to any new protocol.

That does not mean we should twiddle our thumbs and wait. The first step
is to find a way to authenticate radio amateurs without significant
overhead. Unfortunately, there is no globally available fully-automatic
method available. EchoLink and LotW are using manual verification to
issue access codes, IIRC with the LotW using SSL authentication (which
is not only secure but may be also usable for our purpose).

Secondly, we need to change the IS protocol. This depends on how
authentication is performed and only has to change the initial login
step.

Then, we need to create proxy software to allow the use of old IS
clients with new servers. This software can be run on the HAM's PC, load
his certificate and connect to APRS-IS-new servers using proper
authentication.

Finally, we need to shut down the old APRS-IS servers or at least limit
their functionality to RX only to prevent abuse.

This is not an easy process, but it is the only option if you really
want to do something against unauthenticated APRS-IS use, and it needs
to be started now if you really believe that APRS-IS will explode due to
abuse.


Kind regards from Germany,

Georg DO1GL
-- 
APRSdroid - Open Source APRS Client for Android ++ http://aprsdroid.org/m
     ++ https://market.android.com/details?id=org.aprsdroid.app ++
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