[Xastir] IGating

[James Ewen]

On 8/25/07, Steve Friis <wm5z at comcast.net> wrote:

> The hope is that the El Paso, Local an URFMS digi's will lower the hops
> they retransmit.
> See my comment above. I was not thinking that supposition, but the way I
> worded my first comment I can see how you would think that is what I meant.

Aha... now I understand what you meant, not what you typed.

Yes, if you provide an i-gate locally, those who's sole purpose is to
be seen via the internet can use shorter paths, and by doing so,
reduce the total RF load on the network as a whole. Indeed, you've got
the concept.

> Right now, as far as I know, I am the only station IGate equipped in Las
> Cruces. I think that is why El Paso set their digi's for so many hops.

Okay, here's another amibuous interpretation...

What do you mean by the last sentence? The digipeaters don't control
how many hops other set their paths to. If the digipeaters are set to
a large outgoing path, it only affects the packets sent by them, not
packets being digipeated.

Now, under the new n-N paradigm, we suggest blocking long paths, by
trapping them with the aliases programmed into the UIDIGI algorithm in
the KPC-3 TNCs.

It's really hard to make good comments on a system that you can only
observe via the APRS-IS, without any knowledge of the local terrain.
El Paso appears to have 2 digipeaters. ELPASO appears to be located on
a ridge overlooking the city, with a good view of just about
everywhere. It is using the proportional path concept to keep it's own
load down on the network. ELPNE looks like it is a redundant
digipeater. It's only a couple miles NE of ELPASO, in an area that
should have excellent coverage by the ELPASO digi. The proportional
path used by ELPNE shows me that the operator does not fully
understand the new n-N paradigm, as he has an outgoing path of
WIDE1-1, which would trigger home fill-in digipeaters. A main
digipeater should never ask for help from the fill-in digis.

Siting two digipeater close together in overlapping coverage areas
causes a large decrease in the amount of available airtime, and is a
detriment to the APRS network as a whole, rather than contributing to
the network.

The local network appears to support up to 4 hops. With digipeaters
situated on mountaintops, 4 hops can cover a huge distance. I see
JACKPK being heard by BENRDG 250km away which is it's most common
access to the APRS-IS.

With the amount of activity I can see around there, I highly doubt
that 4 hops are needed by anyone. 2 hops in the area would get just
about anyone to an i-gate, and also heard via RF over a huge area.

> This is true. There is a digi on Mt. Franklin which is in El Paso. The
> Upper Rio Grand FM Society has many interconnected digi-peaters in the
> area, but because of location, can not directly IGate. This is because
> of the remoteness of the mountain tops, and the expense of trying to run
> a dedicated phone line to run the internet. These digi's do a fantastic
> job at what they are supposed to do, which is to repeat, so they can be
> heard by an IGate.

ELPASO is only 9.4 km from an i-gate which it hits very well, and gets
i-gated through over 90% of the time. The remote digipeaters don't
need internet access directly, you have a lot of i-gates in the area.
You also have lots of stations using paths that cover huge distances.
Take a look at how far ELPASO hears stations.

http://www.db0anf.de/app/aprs/stations/digiusermap-ELPASO

The best thing anyone can do for their local RF network is user
education. Teach people that long paths are not required. Get them to
reduce thier impact on the local network, and more people will be able
to play, as well as the network reliability will increase. It's a
tough job, but it needs to be done everywhere.

James
VE6SRV