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Troubleshooting advanced network performance features (RSS, NetDMA et al)

Article ID: 2643970 - View products that this article applies to.

Summary

This article is a guide to troubleshooting network performance issues that involve the Windows enhanced networking features including

TCP Connection offloading
Receive side scaling (RSS)
NetDMA
TCP chimney offloading

More information

Check for known "low tech" issues for poor network performance including but not limited to:

Blocked network connectivity

319440
(https://vkbexternal.partners.extranet.microsoft.com/VKBWebService/ViewContent.aspx?scid=KB;EN-US;319440)
: Logon delays occur over a slow connection if opportunistic locking is not granted for the policy file in Windows
2554621
(https://vkbexternal.partners.extranet.microsoft.com/VKBWebService/ViewContent.aspx?scid=KB;EN-US;2554621)
SBSL: NET: Repetitive Query_PATH_INFO requests may cause slow folder access, slow file access and slow user logons
SMB Signing enabled W7 and W2K8 R2 clients communicating over SMB 1.0

Bemis 2709479
(https://vkbexternal.partners.extranet.microsoft.com/VKBWebService/ViewContent.aspx?scid=B;EN-US;2709479)
SBSL: NET: SMB Signing on W7 + W2K8 R2 = slow network i/o over SMB 1
KB 2689311
(http://support.microsoft.com/kb/2689311/EN-US)
SMB commands run serially when the SMB packet-signing feature is enabled ...
Setting EnablePMTUDiscovery = 0 causes the use of 576 byte frames on remote subnets

2709380
(https://vkbexternal.partners.extranet.microsoft.com/VKBWebService/ViewContent.aspx?scid=B;EN-US;2709380)
SBSL: NET: EnablePMTUDiscovery = 0 reduces network throughput
Opportunistic Locking negotiation failure results in the use of 2-byte frame sizes

2576401
(https://vkbexternal.partners.extranet.microsoft.com/VKBWebService/ViewContent.aspx?scid=B;EN-US;2576401)
SBSL: NET: Opportunistic locking negotiation failure results in network reads in 2-byte frame sizes
319440
(http://support.microsoft.com/kb/319440/EN-US)
Logon delays occur over a slow connection if opportunistic locking is not granted for the policy file in Windows
Slow network I/O if PORTFAST is not enabled on spanning tree enabled switches

2714448
(https://vkbexternal.partners.extranet.microsoft.com/VKBWebService/ViewContent.aspx?scid=B;EN-US;2714448)
SBSL: NET: Spanning Tree enabled switches may delay network access if PORTFASTnot enabled
SMB Dialect Negotiation failure results in delayed network I/O

2683028
(https://vkbexternal.partners.extranet.microsoft.com/VKBWebService/ViewContent.aspx?scid=B;EN-US;2683028)
SBSL: NET: SMB Dialect Negot failure causes 1 minute drive mapping delay et al
Windows Server 2008 R2 computers experience slow network I/O if > than 32 GB of RAM installed

2634907
(https://vkbexternal.partners.extranet.microsoft.com/VKBWebService/ViewContent.aspx?scid=KB;EN-US;2634907)
SACK is not used to acknowledge blocks of received packets when a packet reordering/loss situation occurs causing slow network i/o
Configuring network ports in switches with speeds slower than the underlying network

2714923
(https://vkbexternal.partners.extranet.microsoft.com/VKBWebService/ViewContent.aspx?scid=B;EN-US;2714923)
SBSL: NET: Setting network speed to 100MB on switch + "Autodetect" in NCPA.CPL on a gigabit net = SBSL
Repetitive query-path_info network I/O when traversing deep paths or long file names.

2554621
(https://vkbexternal.partners.extranet.microsoft.com/VKBWebService/ViewContent.aspx?scid=B;EN-US;2554621)
SBSL: NET: Repetitive Query_PATH_INFO requests may cause slow folder access, slow file access and slow user logons

Network performance enhancements

The Windows Scalable Networking Pack was released as a stand alone update for Windows Server 2003 SP1, but was later added to Windows Server 2003 Service Pack 2. This was a collection of enhancements to improve network throughput and performance. When installed, they were enabled by default.

These same enhancements are found in Windows Server 2008 as well (plus a few newer ones). The Windows Server 2008 operating system usually turns them on or off automatically, so in most cases, no manual intervention is necessary.

The network enhancements in the operating system are intended to improve network throughput on servers by offloading some networking tasks to the network adapter's hardware. This mostly applies to adapters that are running at 1Gbps and higher connection speeds and require that the network adapters and drivers in use implement the enhancements. If the driver doesn't support the enhancements, or the driver is having a problem related to them, you may need to disable them manually. If you have invested in equipment that supports TCP connection offloading/RSS/NetDMA, and the adapter is not working properly, then the first thing to check should be the driver date. If there is a newer driver for your network adapter, that may resolve any networking issues you may have had.

Determine Driver information in Windows Server 2008 and Windows Server 2008 R2

The date and version of your network driver can be found by:

Click Start > right click Computer and click Manage
Expand the System Tools group in the left pane if needed
Click the Device Manager in the left pane and you should see something like the screen below
Expand the Network adapters in the right pane and double click on the adapter

The Driver tab has the information:

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For Windows Server 2003, follow these steps to get to the Device Manager:

Open the Administrative Tools in Control Panel.
Within the Administrative Tools click Computer Management.
Click on Device Manager

Next, visit the website of the Driver Provider (also on the Driver tab). Check for the latest version of the driver and see if it is newer than the driver date you found in the device properties. You may also find a solution in a FAQ or a forum on the manufacture's site.

If updating the network drivers doesn't work, you might want to try disabling the enhanced features and see if the issue resolves. Use this as a last resort or a troubleshooting step, not as the solution unless your network card has been confirmed not to support the feature(s) in question. The enhanced networking features can be enabled/disabled in the operating system as well as in the network cards advanced settings. Below you can see the Advanced tab in the network adapter properties that shows the TCP Connection Offload and Receive Side Scaling (RSS) settings.

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To see the settings for the operating system, use net shell command "netsh interface tcp show global" command as follows:

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Here are 2 other settings to check that affect TCPchimney offloading are:

netsh interface tcp show chimneyapplications

AND
netsh interface tcp show chimneyports

These commands allow TCP offloading to be set up specifically for a certain application or port combination. Output from both netsh commands is shown below:

n.b. - This operation requires elevated privleges (Run as administrator)

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If they are blank, no applications or ports have been added to the chimney offload settings.

Here are the most common enhanced network features with links to more information on how to enable/disable them:

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

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

TCP Chimney Resources - http://technet.microsoft.com/en-us/network/dd277645

(http://technet.microsoft.com/en-us/network/dd277645)

Receive Side Scaling Resources (RSS) - http://technet.microsoft.com/en-us/network/dd277646

(http://technet.microsoft.com/en-us/network/dd277646)

NetDMA - http://technet.microsoft.com/en-us/library/gg162716(WS.10).aspx

(http://technet.microsoft.com/en-us/library/gg162716(WS.10).aspx)

Windows 2003 Scalable Networking Pack - http://support.microsoft.com/kb/912222

(http://support.microsoft.com/kb/912222)

Networking Deployment Guide: Deploying High-speed Networking Features - http://technet.microsoft.com/en-us/library/gg162681(WS.10).aspx

(http://technet.microsoft.com/en-us/library/gg162681(WS.10).aspx)