TCP Chimney

TCP Chimney Offload 概览

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TCP Chimney Offload是一种在网络数据传输时, 能帮助从CPU上转移网络负载到网络适配器上的network技术. 在Windows Server 2008上, TCP Chimney Offload允许Windows网络子系统能转移对TCP/IP连接的处理到对TCP/IP offload处理有特殊支持的网络适配器上.

 

TCP Chimney Offload在所有版本的Windows Server 2008和Windows Vista上都可用. 如果网络适配器支持这个特性, 那么TCP/IPv4 和TCP/IPv6 的连接都可以被转移.

 

如何在Windows Server 2008上开启和关闭TCP Chimney Offload

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TCP Chimney Offload可以在下列两个地方开启或关闭

• 操作系统
• 网络适配器的高级属性页面

TCP Chimney Offload仅在上面两个地方全都开启的时候才会工作. 默认情况下TCP Chimney Offload在这两个地方都是被关掉的. 然而OEM版的安装有可能会开启这两个地方的选项.

 

如何在操作系统中配置TCP Chimney Offload

• 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

如何在网络适配器中配置TCP Chimney Offload

• 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 Advanced properties page of the network adapter.

下表列出了TCP Chimney与其他程序或network service的能否共存

Program or service	Works together with TCP Chimney Offload	Expected behavior when both the service and TCP Chimney Offload are enabled
Windows Firewall	Yes	If the firewall is configured to allow for a given TCP connection, the TCP/IP stack will offload that TCP connection to the network adapter.
Third-party firewall	Implementation-specific	Some firewall vendors have decided to implement their product in such a way that TCP Chimney Offload can be used while the firewall service is running. Refer to the firewall documentation to find out whether the product you are using supports TCP Chimney Offload.
Internet Protocol security (IPsec) policy	No	If the system has an IPsec policy applied, the TCP/IP stack will not try to offload any TCP connections. This lets the IPsec layer inspect every packet to provide the desired security.
Network Adapter teaming service (This service is also known as the Load Balancing and Failover service. It is usually provided by an OEM.)	Implementation-specific	Some OEMs have decided to implement their network adapter teaming solutions so that they coexist with TCP Chimney Offload. See the network adapter teaming service documentation to determine whether you can use TCP Chimney offload together with this service.
Windows Virtualization (Hyper-V technology)	No	If you are using the Microsoft Hyper-V technology to run virtual machines, no operating system will take advantage of TCP Chimney offload.
Network monitoring tools, such as Network Monitor and Wireshark	Implementation-specific	Some network monitoring tools may coexist with TCP Chimney but may not monitor offloaded connections.
Network Load Balancing (NLB) service	No	If you configure the NLB service on a server, the TCP/IP stack does not offload TCP connections.
Cluster service	Yes	However, note that TCP connections using the Network Fault Tolerant driver (NetFT.sys) will not be offloaded. NetFT is used for fault-tolerant inter-node cluster communication.
Network Address Translation (NAT) service (also known as the Internet Connection Sharing service)	No	If this service is installed and running, the TCP/IP stack does not offload connections.

 

如何确定TCP Chimney Offload是否在工作

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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:

当TCP Chimney Offload 在操作系统和网络适配器中开启的时候, TCP/IP栈会试图把合适的TCP连接转移到网络适配器上. 为了确定哪个当前建立了的TCP连接被转移了, 遵循下面的步骤:

1. 用管理员的权限打开一个命令行窗口.

2. 输入下面的命令, 然后按Enter

     netstat –t

 

你会收到像下面的结果

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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

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这里第二个连接被转移了.

 

摘译自:

Information about the TCP Chimney Offload, Receive Side Scaling, and Network Direct Memory Access features in Windows Server 2008

http://support.microsoft.com/kb/951037