Re: Radio Ethernet Modem Experiences

[franco segna <fsegna () web de>]

For the RF implications and design basics you may take a look at
        http://sandbox.bellanet.org/~onno/the-guide/wifi/
and for some practical considerations at
        http://www.solwise.co.uk/los.htm
but for a solid design you will need an RF engineer (endangered species).

From the security point of view, consider the following:
1. design only single point-to-point encrypted links (you don't need 
dynamic authentication, and the buildings can safely be defined as static)
2. use only highly-directive antennas (as allowed from local 
regulations) to greatly reduce the possibility of detection, decoding, 
attacking or jamming (you will need anyway high-gain antennas to reach 
consistently - 99.0% availability - several thousand feet on 802.11b or 
11g). High directivity means very narrow radiation/receiving patterns; 
any motivated attacker would be forced to use a similar antenna, from a 
location comprised in the narrow radiation lobe, and pointed with great 
precision toward one of the link ends.

Regards
Franco


Bruce Platt wrote:
> This is slightly off-topic.
>
> I'm looking for some information on experiences which you may have with
> Radio Ethernet repeaters.  I need to connect several small LANS in separate
> buildings which are several thousand feet apart and the cost of installing
> fiber is too great.
>
> Data rates will be modest across the entire LAN, so I think I can fit in the
> bandwidth limitations of some of the 908 Mhz Spread Spectrum devices, or
> even the 2.4 Ghz 802.11b devices (wep!).
>
> Using these as bridges seems like a decent way of accomplishing what I need.
>
> Have any of you used these before?  I can think of some of the gotchas,
> like:
>
> 1. Oops, another building is in the way, one more unit needed,
> 2. Signal degradation due to weather,
> 3. Co-ax length from external antenna to device,
> 4. Potential security concerns on WEP units, though the data is not greatly
> sensitive, 
>  ...
>
> However, I can also see some war-driving type risks which I am not competent
> to evaluate, though no dhcp servers will run, and all available LAN
> addresses will be already occupied.
>
> Since one doesn't know what one doesn't know, I am happy to learn from what
> you have to offer.
>
> Thanks and regards,
>
> Bruce
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> firewall-wizards () honor icsalabs com
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--

Franco Segna  -  fsegna () web de
Key fingerprint = 704C 3070 70A0 680A 760D  025E D849 02AB 2309 87A3

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