Hi,

I've tested the latest upstream kernel and it seems the problem still exists.

[hloeung@darkon tmp]$ uname -a
Linux darkon 3.11.10-03111001-generic #201312110635 SMP Wed Dec 11 11:35:43 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux

(from http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.11.10.1-saucy/)

Without 11n_disable=1:

| [hloeung@darkon tmp]$ ping 203.12.160.35 -c 100 | grep -v 'ttl=[[:digit:]]\+[[:space:]]time=[[:digit:]]\{2\}\.'
| PING 203.12.160.35 (203.12.160.35) 56(84) bytes of data.
| 64 bytes from 203.12.160.35: icmp_seq=13 ttl=227 time=1492 ms
| 64 bytes from 203.12.160.35: icmp_seq=14 ttl=227 time=502 ms
| 64 bytes from 203.12.160.35: icmp_seq=18 ttl=227 time=1979 ms
| 64 bytes from 203.12.160.35: icmp_seq=19 ttl=227 time=1001 ms
| 64 bytes from 203.12.160.35: icmp_seq=20 ttl=227 time=1595 ms
| 64 bytes from 203.12.160.35: icmp_seq=21 ttl=227 time=636 ms
| 64 bytes from 203.12.160.35: icmp_seq=26 ttl=227 time=1661 ms
| 64 bytes from 203.12.160.35: icmp_seq=27 ttl=227 time=701 ms
| 64 bytes from 203.12.160.35: icmp_seq=31 ttl=227 time=1321 ms
| 64 bytes from 203.12.160.35: icmp_seq=33 ttl=227 time=565 ms
| 64 bytes from 203.12.160.35: icmp_seq=50 ttl=227 time=719 ms
| 64 bytes from 203.12.160.35: icmp_seq=54 ttl=227 time=1503 ms
| 64 bytes from 203.12.160.35: icmp_seq=55 ttl=227 time=512 ms
| 64 bytes from 203.12.160.35: icmp_seq=56 ttl=227 time=602 ms
| 64 bytes from 203.12.160.35: icmp_seq=60 ttl=227 time=1500 ms
| 64 bytes from 203.12.160.35: icmp_seq=61 ttl=227 time=517 ms
| 64 bytes from 203.12.160.35: icmp_seq=62 ttl=227 time=961 ms
| 64 bytes from 203.12.160.35: icmp_seq=76 ttl=227 time=1439 ms
| 64 bytes from 203.12.160.35: icmp_seq=77 ttl=227 time=450 ms
| 64 bytes from 203.12.160.35: icmp_seq=82 ttl=227 time=1442 ms
| 64 bytes from 203.12.160.35: icmp_seq=83 ttl=227 time=454 ms
| 64 bytes from 203.12.160.35: icmp_seq=88 ttl=227 time=1214 ms
| 64 bytes from 203.12.160.35: icmp_seq=89 ttl=227 time=214 ms
| 64 bytes from 203.12.160.35: icmp_seq=93 ttl=227 time=1182 ms
| 64 bytes from 203.12.160.35: icmp_seq=94 ttl=227 time=667 ms
| 64 bytes from 203.12.160.35: icmp_seq=100 ttl=227 time=1384 ms
|
| --- 203.12.160.35 ping statistics ---
| 100 packets transmitted, 97 received, 3% packet loss, time 99188ms
| rtt min/avg/max/mdev = 17.821/287.165/1979.984/501.613 ms, pipe 2
|
| [hloeung@darkon tmp]$ iwconfig
| lo        no wireless extensions.
|
| wlan0     IEEE 802.11abgn  ESSID:"star-local-5GHz"
|           Mode:Managed  Frequency:5.22 GHz  Access Point: C0:25:06:A6:31:0E
|           Bit Rate=240 Mb/s   Tx-Power=15 dBm
|           Retry  long limit:7   RTS thr:off   Fragment thr:off
|           Power Management:off
|           Link Quality=61/70  Signal level=-49 dBm
|           Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
|           Tx excessive retries:18288  Invalid misc:21   Missed beacon:0

Notice the high Tx excessive retries? Now iwlwifi module reloaded with 11n_disable=1:

| [hloeung@darkon tmp]$ ping 203.12.160.35 -c 100 | grep -v 'ttl=[[:digit:]]\+[[:space:]]time=[[:digit:]]\{2\}\.'
| PING 203.12.160.35 (203.12.160.35) 56(84) bytes of data.
|
| --- 203.12.160.35 ping statistics ---
| 100 packets transmitted, 100 received, 0% packet loss, time 99148ms
| rtt min/avg/max/mdev = 14.929/22.947/62.614/11.495 ms
|
| [hloeung@darkon tmp]$ iwconfig
| lo        no wireless extensions.
|
| wlan0     IEEE 802.11abg  ESSID:"star-local-5GHz"
|           Mode:Managed  Frequency:5.22 GHz  Access Point: C0:25:06:A6:31:0E
|           Bit Rate=54 Mb/s   Tx-Power=15 dBm
|           Retry  long limit:7   RTS thr:off   Fragment thr:off
|           Power Management:on
|           Link Quality=61/70  Signal level=-49 dBm
|           Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
|           Tx excessive retries:0  Invalid misc:155   Missed beacon:0


Hope this helps.


Regards,

Haw