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Troubleshooting / ECN flag set in IP packet > no optimization
« on: 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.
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.