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Bug 559116 - Inability to set MTU of PPTP Tunnel Results In Poor Performance
Inability to set MTU of PPTP Tunnel Results In Poor Performance
Status: RESOLVED FIXED
Product: NetworkManager
Classification: Platform
Component: VPN: pptp
0.7.x
Other All
: Normal minor
: ---
Assigned To: Dan Williams
Dan Williams
Depends on:
Blocks:
 
 
Reported: 2008-11-03 14:37 UTC by John Navarro
Modified: 2009-03-08 03:44 UTC
See Also:
GNOME target: ---
GNOME version: ---



Description John Navarro 2008-11-03 14:37:57 UTC
Please describe the problem:
nm-applet 0.66 provided the ability to set the PPTP tunnel MTU within the configuration settings. nm-applet 0.70 does not provide similar settings. Not being able to set the MTU in nm-applet 0.70 results is a major performance hit with my PPTP connections.

nm-applet 0.70 needs the ability set the PPTP MTU from within the applet itself as the 0.66 release did.

Steps to reproduce:
1. Establish PPTP VPN connection.
2. Attempts to browse or SSH into any server. Stalls are immediate and consistent.




Actual results:
The results of this is a serious performance hit; i.e. lots of packet drops. Usability of the tunnel becomes just about useless. Lots of packet buffering and ACK drop errors reported in syslog.

Expected results:
n/a

Does this happen every time?
Yes

Other information:
My workaround is to set the MTU manually after the tunnel has been created (ifconfig ppp0 mtu 1416). nm-applet 0.66 defaulted to 1416 and that value seems to work well with my Ubuntu Intrepid installation.
Comment 1 William Loucks 2008-11-28 18:43:13 UTC
Please compare network-manager 0.6.6 and network-manager-pptp 0.6.5 to network-manager and network-manager-pptp 0.7 and thereby find many options which do not appear in 0.7. Below is a textual description of pptp dialog window labeled "Edit VPN Connection", a multi-tabbed dialog.

network-manager-pptp 0.6.5
Textual description of the Dialog window labeled "Edit VPN Connection", a multi-tabbed dialog:

Tab labeled "Connection"
  Free-form text entry labeled "Connection Name"
  Checkbox: "Requires existing network connection"
  Drop-down list with only one entry: "Windows VPN (PPTP)"
  Free-form text entry labeled "Gateway"
Tab labeled "Authentication"
  Checkbox: "Authenticate Peer"
  Checkbox: "Refuse EAP"
  Checkbox: "Refuse CHAP"
  Checkbox: "Refuse MS CHAP"
Tab labeled "Compression & Encryption"
  Group labeled "Compression"
    Checkbox: "Require MPPC Compression"
    Checkbox: "Allow Deflate compression"
    Checkbox: "Allow BSD Compression"
  Group labeled "Encryption"
    Checkbox: "Require MPPE encryption"
    Checkbox: "Require 128 bit MPPE encryption"
    Checkbox: "Enable stateful MPPE"
Tab labeled "PPP Options"
  Free-form text entry labeled "Custom PPP options"
  Group labeled "IP Options"
    Checkbox: "Use Peer DNS"
    Checkbox: "Require explicit IP Addr"
    Checkbox: "Exclusive device access (UUCP-style lock)"
    Checkbox: "Debug output"
  Group labeled "Packet Parameters"
    Drop-down list with up/down arrows AND free-form text entry labeled "MTU"
    Drop-down list with up/down arrows AND free-form text entry labeled "MRU"
  Group labeled "Delays and TImeouts"
    Drop-down list with up/down arrows AND free-form text entry labeled "connect-delay"
    Drop-down list with up/down arrows AND free-form text entry labeled "lcp-echo-failure"
    Drop-down list with up/down arrows AND free-form text entry labeled "lcp-echo-interval"
Tab labeled "Routing"
  Checkbox: "Peer DNS through tunnel"
  Checkbox: "Only use VPN connections for these addresses"
    Free-form text entry below which is the text, "example: 172.16.0.0/16 10.11.12.0/24"
Comment 2 William Loucks 2008-11-28 22:58:57 UTC
I just realized I did not explain in my previous comment that that comment is directed at the bug assignee, Dan Williams. Also, I confirm the inability to set MTU. I also require the ability to set refuse-eap, and to set up custom routing so that only some of the traffic goes through the pptp tunnel. How do we go about raising the status of this bug higher than "UNCONFIRMED"?
Comment 3 Dan Williams 2008-11-29 21:32:08 UTC
You can ensure only some traffic is routed through the VPN by adding a custom route to the IPv4 Routes... dialog.  If you have done so, only traffic for that route will be directed through the VPN.
Comment 4 Dan Williams 2009-02-24 00:02:17 UTC
Latest 0.7.1rc1 PPTP plugin uses 1400 as the default MTU.
Comment 5 John Navarro 2009-02-24 14:54:02 UTC
Awsome - thanks so much
Comment 6 peitschie 2009-03-01 03:47:15 UTC
Just to clarify, does the fix mean that there is the ability to set a custom MTU, or simply that the default MTU has changed...?
Comment 7 John Navarro 2009-03-08 03:44:10 UTC
Using the Ubuntu 64bit Jaunty release with the latest updates. When I connect via PPTP ifconfig shows the MTU as 1496 for PPP0. Is this the wrong way to check it?

Here are my versions - do I have the latest code?

Network Manager Version: 0.7.1~rc3-0ubuntu1
Network Mangerr-PTPP  Version: 0.7.1~20090213+bzr15-0ubuntu1

Thank you,
John