Hi!
I have site-to-site L2TP/IPSec connection between CCR1009 over high-latency link (200ms)
both running 6.46.1
one side has 30M/30M connection, another one 300M/15M.
SMB/FTP Speed is pretty bad across this tunnel, so I decided to debug it:
I’ve set up packet capture on both CCRs and ran bandwidth test limited to 1mbit (to make sure that channel saturation is not a factor) from machine in one subnet to machine in another one.
basically I have sniffers on both ends of tunnel.
In capture results I can see packets that enter tunnel on one side, but never exit another, thus triggering “fast retransmission”. Nothing is fast about it though, due to high latency.
tx/rx errors/drops on both sides of tunnel don’t increase.
Number of packets lost is pretty small: approx 10 out of 10000, or 10 per 60 secs.
Also I observe out of order packets time to time, which is not as bad, but still suspicious.
I am not sure either of this may cause speed problems, but fast retransmits definitely affect wnd size.
questions:
- is it normal to have packets reordered while in tunnel?
- is it normal for tunnel to drop packets quietly?
- any typical suspects in settings to look at?
thanks.
Andrey