Slow transfer between 2 networks


#1

Hi everyone.

I have two dedicated servers with OVH.com, one in Canada and the other one in France. OVH have a internal network called “vrack” promising low latency between servers. Both server has XenServer 7.4 as OS.

Only the VyOS virtual machines has internet connection and both servers has a vlan and every virtual machines is connected to last one respectively.

Scenario 01
To connect the private networks I’ve attached a third virtual nic to VyOS and I’ve added a static route.

Now, everything is working, the virtual machines can reached between theirs but the network transfer is very slow up to 221 Kb/s

iperf shows up to 957 Mbits/sec over UDP and up to 94.4 Mbits/sec over TCP.
iperf -c 172.22.12.1 -w 256000 -P 5 -u -b 1000m
iperf -c 172.22.12.1 -w 256000 -P 5

Scenario 02
To connect the private networks I’ve attached a third virtual nic only a specifics virtual machines.

Now, everything is working, the virtual machines can reached between theirs but the network transfer is very slow up to 751 Kb/s

Finally
The OVH.com support team said that the problem is in the VyOS.

¿What you think?

PD. I know my english is not very good, I’m working in that XD.

Thanks in advanced


#3

Do you have access to Xen itself, or is that provide by ovh? If you have access , did you test the speed directly on the hypervisor already? What is the nic config for the VMs? Paravirtualized or fully emulated?


#4

Since UDP gets close to 1Gbps, while TCP performs poorly this is quite possibly a delay/buffer/window related issue. Without knowing the latency between the two end points there is not enough data to determine if a 256K window would be large enough to saturate a 1Gbps link capacity. Typically when dealing with long distance links you either need to tune the end points to account for this or a wan optimization method such as breaking the TCP connection with TCP proxies on either side to handle the window/buffering requirements.

A useful tool to quickly help you gauge the required values without having to do the math is over at speed guide.
https://www.speedguide.net/bdp.php


#5

Sending files between xen speed up to 11 Mb/s, this is ok because I’ve bought 100Mbits/sec vrack port.
Sending files between vyos1 and vyos2 speed up to 10.9 Mb/s, this is ok because I’ve bought 100Mbits/sec vrack port.
The problem is when I try to send a file to the other network using the both vyos, example: WS1121 and WS1221,