How to know if TCP offload is working

How to know if TCP offload is working

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So you went out and got yourself a new server and it came with TOE functionality, and now you're playing Windows 2008 which has TCP offload enabled but you just want to know if its actually offloading traffic.   Here's the only way I know of finding what traffic is offloaded without setting breakpoints in the debugger.

First off to check if TCP offload is enabled:

C:\>netsh int tcp show global
Querying active state...

TCP Global Parameters
----------------------------------------------
Receive-Side Scaling State          : enabled
Chimney Offload State               : enabled <-----
Receive Window Auto-Tuning Level    : normal
Add-On Congestion Control Provider  : ctcp
ECN Capability                      : disabled
RFC 1323 Timestamps                 : disabled

To turn it on/off (does not require a reboot)

netsh int tcp set global chimney=disabled

netsh int tcp set global chimney=enabled

So how do we see if traffic is offloaded?  You run netstat -nt, the 't' dumps their current offload state.   I used findstr just to grab the offloaded connections.

C:\>netstat -nt | findstr /i offloaded
  TCP    110.100.44.52:445      10.5.17.2:1369     ESTABLISHED     Offloaded
  TCP    10.100.44.52:445       1.56.15.14:4741    ESTABLISHED     Offloaded
  TCP    10.100.44.52:49157     1.198.5.2:2444     ESTABLISHED     Offloaded
  TCP    10.100.44.52:49157     1.100.4.219:2255   ESTABLISHED     Offloaded
  TCP    10.100.44.52:49157     1.58.6.50:54620    ESTABLISHED     Offloaded
  TCP    10.100.44.52:49157     1.58.20.40:50442   ESTABLISHED     Offloaded
  TCP    10.100.44.52:49157     1.58.25.15:1191    ESTABLISHED     Offloaded
  TCP    10.100.44.52:49157     1.148.8.6:58308    ESTABLISHED     Offloaded
  TCP    10.100.44.52:49449     1.10.3.2:1025      ESTABLISHED     Offloaded

UPDATE:

Windows 2003 its a bit different:

Netsh int ip set chimney DISABLED

Netsh int ip set chimney ENABLED

Want to know more about Scalable Networking?

http://technet.microsoft.com/en-us/network/bb545631.aspx

Comments
  • Abishek,

    High Importance!

    Did you find a solution to automatically (via a script etc) to disable all the TCP Offload settings? I am urgently looking for a way to do it on approx 300 servers (mix of IBM & HP servers), but all Windows 2003.

    If so, can you post it here please?

    Thanks

  • Algis, I wish I knew how to reach you because I have been having the problem you are having.  DL380 G5 with the 373i drivers under Server 2008 R2, and I cannot get TOE to work.  I have enabled it in Windows, but netstat continues to show all connections in-host.  

    I also am unable to determine if TOE works for NC373i adapters that are teamed through the NCU.  Any ideas?

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  • Some very good conversation and helpful replies. Has answered half of my questions already by reading the comments.
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