Comment 8 for bug 568090

I still have the same problem on a fully updated Maverick (installed from scratch from the 10.10 CD).

Before learning about this nohwcrypt workaround I did a bit of investigation and found the following: The cause of the high and unpredictable latencies is that packets are dropped depending on their size. According to my tests, packet sizes of the form
  size = 128*k + 81 + m
or
  size = 128*k + 105 + m
for any k>=2 and 0<=m<=7

are dropped randomly in 90-95% of the cases. Conversely, all other packet sizes work fine.

You can see for yourself if this is true on your system:
  ping -M do -s 596 www.google.com
should result in 90% packet loss (because 624 = 128*4 + 105 + 7; the 28 byte difference comes from network headers added by ping)
while
  ping -M do -s 597 www.google.com
should result in negligible packet loss.

Hopefully this makes the problem easier to reproduce and analyze!

There are three different workarounds that can solve the problem on my system:
- use the nohwcrypt parameter
- limit the MTU to a value low enough to avoid problematic packet sizes (such as 330 bytes), with "sudo ifconfig wlan0 mtu 330"
- use the madwifi drivers instead of ath5k