Slow file transfer

maxabbr

We have a VPN where file transfers of large files (200MB+) are common but the transfer rate is low (from 0 to 300KB with unstable rate). The transfer is from vpn server to clients or from lan clients (192.168.10.x) to vpn clients (10.8.0.1) and in both cases the transfer is slow.

The both ends has 50/10 Mb. Using other protocols like HTTP or TS the VPN works according to the 50/10 links.

I found lots of topics about this problem but my tweaks speed up the file transfer just a little.

The server (Ubuntu) configuration is:

local vpn.mydomain.x
port 1194
proto udp
dev tun
ca ca.crt
cert vpnserver.crt
key vpnserver.key
dh dh2048.pem
server 10.8.0.0 255.255.255.0
ifconfig-pool-persist ipp.txt
push "route 192.168.10.0 255.255.255.0"
push "dhcp-option DNS 192.168.10.1"
client-to-client
keepalive 10 120
comp-lzo
user nobody
group nogroup
persist-key
persist-tun
status openvpn-status.log
verb 3
# performance tweaks
tun-mtu 1500
tun-mtu-extra 32
fragment 1468
mssfix 1468

The clients (Windows 7/8) configurations is:

client
dev tun
proto udp
remote vpn.mydomain.x
persist-key
persist-tun
ca ca.crt
cert client.crt
key client.key
comp-lzo
verb 3
# performance tweaks
tun-mtu 1500
tun-mtu-extra 32
fragment 1468
mssfix 1468

maikcat

to determine the optimal MTU value ping the server by using

ping -M do -s <size> server

on linux or using

ping -f -l <size> server

on Windows; vary <size> to find the optimal value; I'd start out with 1472 , as that is the default for ethernet networks.
If the MTU needs to be lowered then lower it on both ends

Michael.