[Xastir] UDP frames

[jeff at aerodata.net]

802.11b mac layer is not ax.25. In fact, lots of nice little bells and
whistles we should take advantage of.

Default mode of 802.11b clients is to do a active scan of the channels,
seeking a specific SSID (or in the case of 'all', any ssid). So channel is
almost irrevelent in the case of AP's (BSS).

Consider WRT54G's for your AP's. Not the best, but certainly one of the
most flexiable (run open source linux) and very cheap (street price
$55-65).

Since we are doing low bandwidth applications such as APRS, "store and
forward" will not make large demands on the throughput. The WRT54's (and
many other) AP's support WDS (Wireless Distribution System) mode, which is
a crude form of mesh networking. So, you'd have one connected AP, and then
sprinkle WDS enabled AP's along your proposed route. And remember, the WDS
enabled AP only needs power.



> Thing of coordinating frequency and SSID in adhoc mode just like
> coordinating
> frequency and PL...  Sure there's gotta be coordination.
> /a
>
> J. Lance Cotton wrote:
>> Alan Crosswell wrote:
>>
>>> Bill Vodall wrote:
>>>
>>>> Hmmm.   Taking this a bit further.  Won't an 802.11x device have to be
>>>> in ESS (peer-to-peer mode) instead of IBSS (controlled by an Access
>>>> Point)
>>>> before it can pick up raw UDP packets?    This shouldn't be hard to
>>>> test..
>>>
>>>
>>> Nope.  UDP is just UDP.  What the infrastructure (or lack thereof)
>>> does is irrelevant.  Think of it as working simplex (ESS) vs. working
>>> via a repeater/digipeater (IBSS) is all.
>>
>>
>> Except that if your 802.11b card is blasting away UDP packets in ad-hoc
>> mode with the 'ssid' set to "abcd" and my 802.11b card is sitting next
>> to it in ad-hoc mode with the 'ssid' set to "wxyz", my card doesn't hear
>> anything from yours. So there has to be some amount of coordination.
>> It's obviously not the same as AP association, but it's similar. Kismet,
>> the 802.11 sniffer requires that your wireless card driver allows the
>> card to be put in 'rfmon' mode, which is like promiscuous mode for wired
>> ethernet. There has to be some kind of 'association' using the ssid or
>> you have the equivalent of an ethernet card with no cable plugged in.
>>
>> Now, if we could get a wedge program that would turn on rfmon mode in
>> the wireless driver, then we could have a 1-to-1 equivalent with
>> AX.25/APRS...
>>
>> -Lance
>>
>>> You use UDP all the time when you watch streaming video or other
>>> applications like that which can tolerate some packet loss and keep
>>> working.  You drop some video packets, the picture just gets a little
>>> jumpy but it keeps working.
>>>
>>> /a
>>>
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>>
>>
>>
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