Trouble shooting low rate MCS9 in 802.11ac

Ben Greear greearb at
Tue Aug 19 11:26:57 PDT 2014

On 08/18/2014 02:45 AM, Vu Hai NGUYEN wrote:

> 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.

Also, do you get different results if you use Open v/s WPA2 encryption?

A test I just ran showed decreased performance on one of my systems
when I ran with open v/s wpa2 (400Mbps v/s 350Mbps, UDP goodput).
This was using hardware-crypt, so I expected it to be as fast as Open.
I'm running customized firmware and driver, so maybe that is cause of
slowdown...curious what results others are seeing though!

> I installed tc from package iproute2 and did : tc qdisc but it doesn't improve the performance
> One more question: Could the antennas create any effect on the MCS in use?
> We are using this antenna from PCTEL:
> And in the specification, I saw that it supports the standard 802.11n, so may be this is the reason
> that the best rate for me is MCS7?

Antenna and orientation matter, but the one you list advertises itself
as dual-band, so it looks like it should work well in the 5Ghz band
that AC uses.

You might try changing orientation and/or trying some different


Ben Greear <greearb at>
Candela Technologies Inc

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