[strongSwan] Latency and throughput
sangdrax8 at gmail.com
Fri Dec 11 22:17:47 CET 2015
I am having some problems with throughput in situations with high BPD. If
anyone has some suggestions it would be much appreciated.
My setup is currently as follows:
2 Ubuntu boxes running Strongswan 5.3.2 and kernel 3.13.0-71-generic. I am
using IKEv2 (don't think that matters), ESP in tunnel mode, with
aes256-modp3072-esn, and I set the replay_window=0. I connect both devices
through a third box that I use to adjust the latency between the devices.
If I do not increase latency, I can iperf3 between both servers at 900's
Mbps, both with and with out encryption. The boxes don't show any
significant load, so I wouldn't expect to have hardware issues after the
latency between them increases. As I increase latency, my throughput
starts to go down if ipsec is used. With latency of just 30ms, I see a 1
minute test push near 600 Mbps. If I simply turn off ipsec, and run the
same test, I hit 900's with in the first 2-3 seconds and stay there.
This gets much worse as I jump up to 100ms. With some TCP tuning, my
unencrypted transfer reaches the 900's with in about 10 seconds. My
encrypted transfer just hovers around 100Mbps. I only achieved this after
reading a previous post about the replay_window. With replay window on I
wasn't able to push even 10Mbps.
This feels like the replay_window, or the TCP tuning with tcp_rmem/wmem
that I needed to do to account for the extra packets that are in flight
over the link with such high latency and bandwidth. ESP isn't TCP, so I
have increased wmem_default, wmem_max, rmem_default, and rmem_max to all be
the max value I used when doing my TCP tuning, but I still get the 100Mbps
Any suggestions/pointers as to other tuning steps that might be needed to
ensure packets are sent at the higher rate I know this setup can achieve?
Is there still some replay_window type delays taking place here that I have
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