Multiple WMP11 prism 2 cards in one machine leads to garbled packets? Jouni, help please!

From: evert (
Date: 2002-09-04 21:41:39 UTC

Hi all,

We have the following problem:
We run an accesspoint with a siemens scenic PI 200MMX machine with 3 Linksys wmp11 cards.

In the first instance the test configuration seemed to be working. Association and ping's were possible from outside to all cards in master and managed mode.

The real configuration is as follows:
- 1 card is the real accesspoint ( master mode ) on an Omni antenna.

We tested this confuguration by association and pinging and found the system working.

Later, it seemed that when large packets were send through the system ( pings of 4000 bytes and above ) the machine was garbling up the packets and dropping a lot of packets due to this garbling. With packets smaller than this amount there seemed to be no problem with garbling up the packets.

Looking deeper into this i realised that this could be an IRQ timing problem whcih the driver or our IRQ controller couldn't handle. a cat /proc/interrupts gave the following: cat /proc/interrupts
oot_at_CNodeCope root]# cat /proc/interrupts

  0:   18400995          XT-PIC  timer
  1:        440          XT-PIC  keyboard
  2:          0          XT-PIC  cascade
  8:          3          XT-PIC  rtc
  9:    4800386          XT-PIC  usb-uhci, wlan1, wlan2, eth0
 10:    3893018          XT-PIC  wlan0
 14:     267996          XT-PIC  ide0
 15:         19          XT-PIC  ide1
NMI:          0
ERR:          0

When we moved all the wlan cards to a separate IRQ the above described problem seemed to be solved. No card is sharing an IRQ anymore ( i thought PCI could handle shared IRQ's ? ) After some heavy testing, the problem reappeared, but with packets bigger then 64000bytes. Beyond this packet size, nothing is wrong.

It is not an interference problem.

what could this be?

Evert Verduin
( Free accessible Wireless network in Leiden the netherlands )

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