Upload problem after setting up global upload speed limit

[doctor46]

I have VPN connection and my upload speed is 3750 Kb/s. When I set global upload limit to 1600 Kb/s (for example), upload speed drops to 0 after a couple of minutes but local network upload speed still is OK. After a few minutes upload speed recovers again for some time but if I cancel upload limit it recovers immediately. What's the problem? Thanks.

[Switeck]

bits versus BYTES mismatch?

uTorrent's global upload limit is in KiloBYTES/second, so 1600 KiloBYTES/second is very close to 13000 kilobits/second.

[doctor46]

bits versus BYTES mismatch?

uTorrent's global upload limit is in KiloBYTES/second, so 1600 KiloBYTES/second is very close to 13000 kilobits/second.

No mismatch. Exactly 1600 kilobytes or 1.6 megabytes.

[Switeck]

And your VPN connection is capable of ~30000 kilobits/second?

Because most connections are measured in kilobits/second OR megabits/second.

[doctor46]

And your VPN connection is capable of ~30000 kilobits/second?

Because most connections are measured in kilobits/second OR megabits/second.

Yes, I have optic fiber 30/30 Megabits.

[Switeck]

A VPN may not run stable at 30 mbit/sec even if your optic line is that fast.

Since the VPN is also dependent on the remote VPN server, if there's a hiccup anywhere your speeds will drop.

From http://www.smallnetbuilder.com/security/security-howto/30353-how-to-set-up-a-site-to-site-vpn-with-openvpn?start=4

"To get a better look at OpenVPN's true performance, I set up both the server and client locally connected through a gigabit switch and transfered some files through them over SMB. Direct transfer (without OpenVPN) clocked in at around 38 Mbps. The same transfer over an encrypted tunnel was barely able to top 4 Mbps. But again, unless you have top-tier fiber-based connections on both ends of your encrypted tunnel, you're unlikely to be limited by OpenVPN itself."

Even the absolutely monstrous NETGEAR ProSafe SRX5308 Gigabit Quad WAN SSL VPN Firewall...didn't get good results for VPN:

http://www.smallnetbuilder.com/lanwan/lanwan-reviews/31139-netgear-prosafe-srx5308-gigabit-quad-wan-ssl-vpn-firewall-reviewed?showall=&start=3

"Netgear specs the SRX' IPSec VPN throughput with 3DES tunnel encryption as 180 Mbps. But our results in Table 3 were nowhere near that."

The performance of an SSL tunnel was even more dismal.

1st and 2nd links in my signature for more conservative settings may help reduce how often these slowdowns occur, but it remains to be seen whether your setup plus the remote end and intervening parts of the internet are capable of >10 mbit/sec VPN speeds.