Wan Optimization Support

Technical => Troubleshooting => : gg December 19, 2014, 01:03:54 PM

: ECN flag set in IP packet > no optimization
: gg December 19, 2014, 01:03:54 PM

Hello! I have the following issue:

Optimization of traffic from/to a Windows Server 2012 (R2) is not working because they use the Data Center Transmission Control Protocol. With this protocol, ECN (Explicit Congestion Notification) is enabled by default (see: http://technet.microsoft.com/en-us/library/hh997028.aspx).

I checked this with tcpdump and a packet with an ECN flag misses the "optimization flag" (see: http://wanos.org/wiki/index.php?title=Optimization). The peer status stays down.

If I disable ECN on one Windows Server (netsh interface tcp set global ecncapability=disabled), the "optimization flag" is set. The problem (peer down) occurs only if both sides ("client" and server) have ECN enabled.

Because ECN is only enabled by default on Windows Server 2012 (R2) systems (not Windows 8/8.1) this is probably only a minor issue.

: Re: ECN flag set in IP packet > no optimization
: ahenning December 19, 2014, 01:23:11 PM

Great info, thank you very much. I'll check it and see what is needed to resolve. Would it be possible to upload the tcpdump with the packet with the ECN bit set?

As a work around until then, does UDPENCAP solve the problem?

To enable UDPENCAP use the settings tab in the web interface.

: Re: ECN flag set in IP packet > no optimization
: gg December 19, 2014, 02:43:23 PM

I just checked with UDPENCAP=Enable and it seems to work.

Unfortunately I can come back on this issue in two weeks first. Then I will post the requested dump files.

: Re: ECN flag set in IP packet > no optimization
: ahenning December 19, 2014, 02:53:45 PM

Ok thanks for the info. The issue has been found and fixed. Update will be in v1.5.0

: Re: ECN flag set in IP packet > no optimization
: ahenning March 11, 2015, 04:37:39 PM

Hi gg, It would be great if you time to perhaps re-test this with the update in.