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On 7/28/2010 10:29 PM, Brett Friermood wrote:
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cite="mid:AANLkTi=A5h4HYWQMiozWvwgcv9jAmtYc0go2rO0L-mKM@mail.gmail.com"
type="cite">
<pre wrap="">On Wed, Jul 28, 2010 at 11:56 PM, Adi Linden <a class="moz-txt-link-rfc2396E" href="mailto:adil@adis.on.ca"><adil@adis.on.ca></a> wrote:
</pre>
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<pre wrap="">
I've read the docs you've recommended. I suppose I am interested in a lot more detail. In order
for a message to make it from IS to RF, does the iGate need to listen to the complete IS data
stream? Or is there a mechanism that allows an iGate to forward the "heard" list to upstream
server(s) to establish a path for messaging?
</pre>
</blockquote>
<pre wrap="">
The IS is smart. It knows which stations have been heard by which
IGates.
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<br>
Actually the APRS-IS does NOT make these decisions. The decision
to gate or not gate IS-to-RF is made by each igate. APRS-IS
servers constantly exchange data with each other. It does not
matter which APRS-IS server an igate connects to. The igate will
receive the same data from the IS, as determined by the user-defined
filters. <br>
<br>
Every igate maintains a table of stations heard on RF. If a given
station was heard recently (typically within the last half hour or
hour) and is considered local (meaning typically heard direct or via
only a single digi hop), any messages bound for that station from
the Internet will be grabbed from the IS stream and re-transmitted
on RF. <br>
<br>
When a mobile moves from the local area of an igate (or shuts down),
the station will be dropped from the "locals heard" list of the
igate after a half-hour or hour or so. As a result that particular
igate will quit grabbing messages for that mobile from the IS, and
will stop transmitting them on RF. Hopefully, by that time, the
mobile has moved into the local area of another igate where the
process repeats itself. <br>
<br>
In other words, for a message on the Internet to get to a mobile,
the mobile must have been heard first on RF recently and nearby by
an igate. Further, that igate must be explicitly configured for
"reverse-gating". <br>
<br>
<br>
<br>
<hr size="2" width="100%"><br>
--<br>
<br>
Stephen H. Smith wa8lmf (at) aol.com <br>
EchoLink Node: WA8LMF or 14400 [Think bottom of the 2M
band]<br>
Skype: WA8LMF<br>
Home Page: <a class="moz-txt-link-freetext" href="http://wa8lmf.net">http://wa8lmf.net</a><br>
<br>
NEW! *** HF APRS over PSK63 ***<br>
<a class="moz-txt-link-freetext" href="http://wa8lmf.net/APRS_PSK63/index.htm">http://wa8lmf.net/APRS_PSK63/index.htm</a><br>
<br>
Universal HF/VHF/UHF Antenna Mounting System<br>
<a class="moz-txt-link-freetext" href="http://wa8lmf.net/mobile/UniversalAntMountSystem.htm">http://wa8lmf.net/mobile/UniversalAntMountSystem.htm</a><br>
<br>
"APRS 101" Explanation of APRS Path Selection & Digipeating <br>
<a class="moz-txt-link-freetext" href="http://wa8lmf.net/DigiPaths">http://wa8lmf.net/DigiPaths</a> <br>
<br>
<br>
<br>
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