Re: IBSS and BSS with multiple FreeBSD Wireless Gateways

In message: <[email protected]>
            richard childers <[email protected]> writes:
: You are WiFi- and FreeBSD-enabled; so is your friend. For the sake of
: simplicity let's assume that you are directly across from one another in two
: dormitories at approximately the same height.
: 
: You both eliminate signal strength and signal security issues with
: line-of-sight antenna pointed directly into one another's cone of
: transmission.

Well, except that it is real easy to intercept the side lobes of most
antennas if you have proximity.  I routinely am able to sniff packets
off of dish antennas that have a very small cone of transmission by
being very close.

: At this point you are not unlike two routers with a cable between them, and
: it is only a matter of picking an appropriate class 'C' subnet (IE,
: 192.something), assigning it an appropriately long mask (IE, one preserving
: only two bits of the address for actual networking), bringing the interfaces
: up and adding routing entries on each end.

Yes.  I'm doing exactly what you suggest over 5.5 miles between my
house and a friend's.

: Note that your network is still hypothetically subject to eavesdropping and
: jamming from parties in either antenna's line of sight.

This is a real threat.

: A slightly more complicated scenario emerges when you attempt to add a third
: node; at this point one of the nodes needs to have two cards, with two
: addresses and two antennas and two routing entries.
: 
: I imagine there are some issues with crosstalk between the antennas that
: would need to be addressed with physical separation and maybe some
: appropriate shielding; tin foil works, I expect.

Tinfoil won't cut it, I'm afraid.  I've tried to shield things with
tinfoil and found that it was woefully inadequate, even when well
grounded.

Cross talk between antennas is a real problem.  I have two on my roof
and have found that if I run them at the same frequency that there are
big problems.  I have to run them at different frequencies to make
that work.  And I gotta make sure that any access points I have inside
are on a third frequency, otherwise you get mutual interference when
there's lots of traffic.

Warner

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