Configure TCP Chimney Offload in Windows Server 2008

Enable and disable TCP Chimney Offload in Windows Server 2008

TCP Chimney Offload can be enabled or disabled in the following two locations:

The operating system
The advanced properties page of the network adapter

TCP Chimney Offload will work only if it is enabled in both locations. By default, TCP Chimney Offload is disabled in both these locations. However, OEM installations may enable TCP Chimney Offload in the operating system, in the network adapter, or in both the operating system and the network adapter.

How to configure TCP Chimney Offload in the operating system

• To enable TCP Chimney Offload, follow these steps:
  1. Use administrative credentials to open a command prompt.
  2. At the command prompt, type the following command, and then press ENTER:
     netsh int tcp set global chimney=enabled
• To disable TCP Chimney Offload, follow these steps:
  1. Use administrative credentials to open a command prompt.
  2. At the command prompt, type the following command, and then press ENTER:
     netsh int tcp set global chimney=disabled
• To determine the current status of TCP Chimney Offload, follow these steps:
  1. Use administrative credentials to open a command prompt.
  2. At the command prompt, type the following command, and then press ENTER:
     netsh int tcp show global

How to configure TCP Chimney Offload on the network adapter

• To enable or disable TCP Chimney Offload, follow these steps:
1. Open Device Manager.
2. Under Network Adapters, double-click the network adapter that you want.
3. On the Advanced tab, click Enabled or Disabled in the box next to the TCP offload entry. 
   
   Note Different manufacturers may use different terms to describe TCP Chimney Offload on the Advancedproperties page of the network adapter.

How to determine whether TCP Chimney Offload is working

When TCP Chimney Offload is enabled in the operating system and in the network adapter, the TCP/IP stack tries to offload suitable TCP connections to the network adapter. To find out which of the currently established TCP connections on the system are offloaded, follow these steps:

1. Use administrative credentials to open a command prompt.
2. Type the following command, and then press ENTER:
   netstat –t
   You receive output that resembles the following:

   Active Connections
   
     Proto  Local Address          Foreign Address        State           Offload State
   
     TCP    127.0.0.1:52613        computer_name:52614       ESTABLISHED     InHost
     TCP    192.168.1.103:52614        computer_name:52613       ESTABLISHED     Offloaded
   

   In this output, the second connection is offloaded.

How to enable and disable RSS in Windows Server 2008

To enable RSS, follow these steps:

1. Use administrative credentials to open a command prompt.
2. At the command prompt, type the following command, and then press ENTER:
   netsh int tcp set global rss=enabled

To disable RSS, follow these steps:

1. Use administrative credentials to open a command prompt.
2. At the command prompt, type the following command, and then press ENTER:
   netsh int tcp set global rss=disabled

To determine the current status of RSS, follow these steps:

1. Use administrative credentials to open a command prompt.
2. At the command prompt, type the following command, and then press ENTER:
   netsh int tcp show global

When you use a command to enable RSS, you receive the following message:

TCP Global Parameters
----------------------------------------------
Receive-Side Scaling State : enabled