Trouble shooting low rate MCS9 in 802.11ac

Kalle Valo kvalo at
Wed Aug 20 07:51:35 PDT 2014

Vu Hai NGUYEN <vh.nguyen at> writes:

>>> I'd cleaned all rules of iptables and removed all modules of
>>> iptables from kernel by command modprobe -r But there's still some
>>> process of netfilter process running. I disabled netfilter on
>>> bridge interface by writing 0 to these files:
>>> /proc/sys/net/bridge/bridge-nf-call-arptables
>>> /proc/sys/net/bridge/bridge-nf-call-iptables
>>> /proc/sys/net/bridge/bridge-nf-call-ip6tables
>>> and the performance increases from 500 to 550 Mbps (iperf in tcp
>>> reports between 530 ~ 570Mbps). There is no more process like
>>> "br_nf_pre_routing" and "br_nf_forward_ip". Do you think I can do
>>> anything more to strip down netfilter?
>>What do you get for UDP? That seems like pretty good TCP throughput.
> In VHT80 mode and rate forced to NSS3:MCS7, I can obtain 750 Mbps with
> less than 1% data lost (in both way, AP to STA and vice versa).
> Normally I can obtain 2/3 theory rate in practical (for expl NSS3:MCS3
> has 390 Mbps in theory, and if I force to that rate, my TCP throughput
> is around 270 Mbps). So I should obtain 650 Mbps in practical for TCP
> with NSS3:MCS7 (975 Mbps in theory). 570 Mbps is so far to 650 Mbps :(

Forcing the data rate isn't really optimal. Have you tried 10.2
firmware? I was told it has improvements in the rate control algorithm.

Kalle Valo

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