VPN causes slow network connections

[Nathan Clemons]

Binary package hint: network-manager

I have a split VPN config, so that only network traffic destined for my office and production environments goes across the VPN. Normal traffic goes out my regular internet connection.

After upgrading to Natty, I have found a significant performance loss dealing with connections. I have verified that the split VPN config is still working with traceroutes, it is not sending all traffic over the VPN. I have also tried using nscd in case it was a DNS problem, but it is not.

A timed ssh to an internet server, while on the VPN:

real 0m27.321s
user 0m0.000s
sys 0m0.000s

The same server, same command, while not on the VPN:

real 0m1.241s
user 0m0.000s
sys 0m0.000s

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: network-manager 0.8.4~git.20110319t175609.d14809b-0ubuntu2
ProcVersionSignature: Ubuntu 2.6.38-7.39-generic 2.6.38
Uname: Linux 2.6.38-7-generic x86_64
NonfreeKernelModules: nvidia
Architecture: amd64
CRDA: Error: [Errno 2] No such file or directory
Date: Fri Apr 8 11:32:50 2011
IfupdownConfig:
 auto lo
 iface lo inet loopback
InstallationMedia: Ubuntu 10.04.1 LTS "Lucid Lynx" - Release amd64 (20100816.1)
Keyfiles: Error: [Errno 2] No such file or directory
NetworkManager.state:
 [main]
 NetworkingEnabled=true
 WirelessEnabled=true
 WWANEnabled=true
ProcEnviron:
 LANGUAGE=en_US:en
 PATH=(custom, user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
RfKill:

SourcePackage: network-manager
UpgradeStatus: Upgraded to natty on 2011-04-01 (7 days ago)

[Mathieu Trudel-Lapierre (cyphermox)]

Could MTU be too high or too low for that connection? Or maybe compression can be adjusted to make sure it doesn't impact CPU time for the connection?

These details are pretty specific to the environment you use a VPN in; I think they should be checked too.

As a way to try and measure impact of configuration, could you try to use a config as simple as possible, possibly avoiding split-tunnel, just to check whether delays are still visible in that case?

Thanks.

[Nathan Clemons (stormerider)]

The MTU on the VPN connection shouldnt affect traffic not destined for that connection, though, should it? And where can I tune the compression levels on a PPTP connection?

I did try using a full VPN configuration and still see the same problem. If I run "ssh -v <host>", I see the delay between the following lines:

debug1: Connecting to <host> port 22.
debug1: Connection established.

Once the connection is established, everything runs fine. Disconnecting from SSH and reconnecting, everything runs through quickly. At a guess, I would think this is something to do with routing decisions which get cached afterwards. On the split VPN config, there is no difference in the lag between items on the VPN and off the VPN; both are affected equally, which again makes me think it's something related to the routing decisions.

[Adam Pollock (thehollyhopdrive)]

I can confirm I am also experiencing this issue. When connected to the VPN and split tunnelling between the local LAN and the VPN, connections to both are extremely slow, exactly as described in the above issue. This issue was not present in previous versions (10.04 and 10.10) and has only started occurring upon upgrading to 11.04 without any change to the VPN configuration.

Description: Ubuntu 11.04
Release: 11.04
network-manager:
  Installed: 0.8.4~git.20110319t175609.d14809b-0ubuntu3
  Candidate: 0.8.4~git.20110319t175609.d14809b-0ubuntu3
  Version table:
 *** 0.8.4~git.20110319t175609.d14809b-0ubuntu3 0
        500 http://gb.archive.ubuntu.com/ubuntu/ natty/main amd64 Packages
        100 /var/lib/dpkg/status

As a measure of comparison I've also included the timings for SSH when the VPN is connected and when it is not (both SSH connections are to a machine connected to the local LAN).

With VPN:
real 0m16.061s
user 0m0.010s
sys 0m0.000s

Without VPN:
real 0m0.561s
user 0m0.000s
sys 0m0.010s

Both of the above examples are timed up to the moment the enter password prompt is displayed.

I've attached the apport information for network-manager from my system. If you need any further information I'd be happy to supply it.

[Launchpad Janitor (janitor)]

[Expired for network-manager (Ubuntu) because there has been no activity for 60 days.]

[Brenden Soares (brenden-y)]

this should not be expired, I'm having this exact problem on Ubuntu 12.04 with openvpn.

[James Shailes (jshailes)]

I agree, I'm experiencing this in 10.04

[maxubu (max-calderoni)]

Same here with Juniper, Ubuntu 12.04