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Re: Using NetBSD as a travel router

On Sun, Dec 31, 2017 at 09:28:54AM -0500, Thor Lancelot Simon wrote:
> The "travel router" use case is even trickier -- the device has to
> participate in one network as a client while participating in another as
> an AP.  Presumably on different channels.

There have been 802.11 adapters that let you operate both as client
and AP on the same channel, but NetBSD would need the "virtual AP"
improvements to net80211 (or the moral equivalent) to do that.

Years ago, a research project (at Microsoft, I think) showed one adapter
participating simultaneously in networks on more than one channel by
exploiting the 802.11 power-save features: essentially, the adapter
would tell one AP it was going to sleep, tune a different channel, talk
to a second AP for a while, tell the second AP it was going to sleep,
tune back to the first channel and "wake" there.  (IIRC, it takes only
microseconds to tune a new channel.)  I believe background scanning is
performed using a similar trick.

There were a lot of buggy power-save implementations at the time the
research was performed, so I think that a lot of people shrugged off the
multiple-channel operation as impractical.  I don't know if it is more
or less practical, now.


David Young    Urbana, IL    (217) 721-9981

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