Re: ath0 timeout problem - again

JoaoBR wrote:
On Saturday 30 December 2006 18:37, Sam Leffler wrote:
JoaoBR wrote:
572 cabq frames transmitted
11 cabq xmit overflowed beacon interval


media: IEEE 802.11 Wireless Ethernet DS/11Mbps mode 11b <hostap>
So one other thing came to mind. If your ap is operating in 11b and you
have many multicast frames q'd up for power save stations then they can
effectively saturate the network if they are being trasnmitted at a low
tx rate (which they would be). This can effectively DOS your wireless
network because the frames are burst immediately following the beacon.


hum, let's see ...

this is an ISP environment
as unlikely the AP goes to sleep while rx/tx the client station either

Don't know where this comment came from. Noone ever suggested the
machine operating as an ap goes to sleep.


we block incoming traffic, we sell internet access so there will no access to
the station which might match the case you brought up, the station request
access to a site and get reply, when the station "sleeps" (if) then there is
no considerable tx to it


The driver limits the burst interval so it does not overflow into the
next beacon but it's allowed to fill all available time to the next
beacon frame (something I've considered changing for just the reason I
described). This has always been an issue. You might try rate limiting
these frames or just hack the driver to violate the spec and not buffer
them for tx after the beacon (to see if your problem goes away).

ok I understand, this certainly is another point we have problems with but we
did exactly what you mentioned.

The tx buffer on the AP, once getting used is never released even if never
getting to fill it up to the configured limit - this I consider so far a
problem but not related to the problem we discuss

Sorry I do not understand this but you say it is not related.



but let me ask, certainly the same problem could come up when for instance the
client has a bad signal (bad caox or connector, antena misplaced or local
interference) and the AP can not tx to this station in this exact moment when
his signal drops right?

Sorry, again I do not understand your point. I guess you're asking how
do people deal with radio sources jamming the frequency, there's nothing
you can do if someone doesn't honor the 802.11 protocols.




Further, if you have a machine with a crappy pci bus (such as !4801
soekris boards) it's entirely possible that you are hoarding the bus
with these long transmits s.t. other problems are occurring. I do not
recommend building ap products out of such equipment. (No disrespect to
the 4501, et al they just had substandard pci bus operation.)


ok, like said before we use PCs and the MBs we use are pretty reliable because
on POPs where this special case of traffic do not appear we have them up for
months even with higher traffic as I mentioned before.


thank you for your availability to help.



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