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Old 07-31-2007, 02:38 AM   #1
nehsmac
LQ Newbie
 
Registered: Jul 2007
Posts: 2

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ppp stalls - tcp packet number reset?


My VPN connection to my work server is experiencing stalls / timeouts. This issue only seems to occur when I connect through linux. WinXP connections do not seem to experience this. In Linux, I am currently using gnome network manager, but the problem also occurred when I was using pptpconfig. This issue seems to be related to the expected TCP packet number suddenly jumping to a higher value. Here is an example of the output from /var/log/daemon.log:

Jul 31 00:49:13 nhamilton-ubuntu pptp[14136]: anon log[decaps_greptp_gre.c:407]: buffering packet 11685 (expecting 11679, lost or reordered)
Jul 31 00:49:13 nhamilton-ubuntu pptp[14136]: anon log[decaps_greptp_gre.c:407]: buffering packet 11686 (expecting 11679, lost or reordered)
Jul 31 00:49:13 nhamilton-ubuntu pptp[14136]: anon log[decaps_greptp_gre.c:398]: discarding duplicate or old packet 11687 (expecting 11744)
Jul 31 00:49:13 nhamilton-ubuntu pptp[14136]: anon log[decaps_greptp_gre.c:398]: discarding duplicate or old packet 11688 (expecting 11744)

When I monitor the log during network operations, I do notice a lot of the "buffering packet #, expecting packet #" messages, but I assume that is just normal TCP protocol for dropped/lost packets. At some point the expected packet number jumps to a larger number (11744 in this example) and the buffering messages turn into the "discarding duplicate or old packet" messages. The discard messages continue to spam the log until I kill the connection, and all network traffic times out during this period. This does seem to occur most frequently when I attempt to perform high throughput operations, such as SCP'ing a large set of files or performing a subversion checkout on large binary files.

So far I have not been able to find much on this issue. The only troubleshooting I have come across is changing options in the /etc/ppp/options file, such as changing the values for lcp-echo-interval and lcp-echo-failure, which has not helped.

Here are the relevant configuration options I am using for gnome network manager:
- Type: PPTP (Windows VPN)
- Refuse EAP
- Require 128-bit MPPE encryption
- Use Peer DNS
- Exclusive device access (UUCP-style lock)
- Peer DNS through tunnel

Has anyone experienced similar issues with vpn connections?
 
  


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