[Xastir] UDP frames

[jeff at aerodata.net]

You can be the worst internet protocol bigot in the world, and you'd still
be a member of the good 'ole boys club if you use WDS.

The MAC layer is BELOW the IP/TCP layer. It is transparent. You and and
the RFC good 'ole boys don't know its there (nor should they). When we
used to run tcp/ip on ham radio, our MAC layer was ax.25, which is quite
unique.



> I'm sorry but I'm a committed Internet Protocol bigot.  I would never use
> a MAC
> layer feature that is unique to only a given Mac implementation.
> /a
>
> jeff at aerodata.net wrote:
>> 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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>>
>>
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