SMS: Systems Management Server May Inaccurately Detect Link Speed (321310)


The information in this article applies to:

  • Microsoft Systems Management Server 2.0
This article was previously published under Q321310

SYMPTOMS

The Systems Management Server (SMS) client's slow link detection for distribution points is not always reliable and you may have the following problems:
  • Advertisements configured as "Assignments are not mandatory over slow links" may run over slow links, for example wide area networks (WANs) and modems.
  • SMS may report Local area network (LAN) links as slow links. This may stop advertisements from running.
The most common problem is that SMS Available Programs Manager (APM) calculates the link speed to be too fast. When this occurs, you may receive log entries that are similar to the following log entries in the Smsapm32.log file:

SCHEDULER : Attempting to get the Slow Network Threshold Speed setting.
SCHEDULER : Attempting to get a Client Properties setting.
SCHEDULER : Failed to get value for specified setting 'Slow Network Threshold Speed'.
SCHEDULER : Attempting to get a Site System Software Distribution setting.
SCHEDULER : The setting 'Slow Network Threshold Speed' currently has a value of 40000.
SCHEDULER : This client has a Slow Network Threshold Speed setting of 40000 bps for site WP1.
SCHEDULER : Successfully obtained a Slow Network Threshold Speed setting.
SCHEDULER : The path's Slow Network Threshold Speed is 40000 bps.
SCHEDULER : Path '\\server\SMSPKGD$\S0100001\' is accessible.
SCHEDULER : Remote Name is \\server\SMSPKGD$
SCHEDULER : Calculated Speed = 800000 bps
SCHEDULER : Fast link detected

For additional information about the "Assignments are not mandatory over slow links" setting, click the following article number to view the article in the Microsoft Knowledge Base:

202332 SMS: How the Assignments Are Not Mandatory Over Slow Links Feature Works

CAUSE

APM uses the MultinetGetConnectionPerformance API to determine link speed and this API does not always return the correct link speed. For additional information about the MultinetGetConnectionPerformance API, click the following article number to view the article in the Microsoft Knowledge Base:

237443 MultinetGetConnectionPerformance() May Not Return Expected ResultsMultinetGetConnectionPerformance() May Not Return Expected Results

RESOLUTION

To resolve this problem, obtain the latest service pack for Systems Management Server version 2.0. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

288239 SMS: How to Obtain the Latest Systems Management Server 2.0 Service Pack

STATUS

Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article. This problem was first corrected in Systems Management Server 2.0 Service Pack 5.

MORE INFORMATION

Starting with SMS 2.0 Service Pack 5 (SP5), a new slow link detection method has been added to APM. In SMS 2.0 SP5, you can configure APM to copy a test file over the link and to calculate its speed based on how long it takes to copy the file. By default, SMS 2.0 SP5 uses this detection method when the test file (Netspeed.dat) described later in this article is present on a distribution point. Otherwise, SMS 2.0 SP5 uses MultinetGetConnectionPerformance the same way as in previous versions. To change the slow link detection method that APM uses, you must edit the registry. After you edit the registry, the next time that SMS Distribution Manager updates a package, it either removes the test file or places the test file on the distribution point depending on the current settings. This article discusses the registry settings later.

The network link speed test file, Netspeed.dat, is copied to the SmsRootFolder\Bin\operating system directory on the SMS site server when the Service Pack installs.

By default, the Netspeed.dat file is 3,400 bytes. This file size works well with link speeds up to 512kbps. Faster links on such a small file produce more unreliable results. The new detection method is not tied to any specific file size and supports sizes from 1 byte up to 4 GB. An SMS administrator can replace Netspeed.dat with a larger or smaller file to make sure the link speed test is satisfactory for the environment. Typically, results are more reliable when the file size is larger. For example, if you are working with WAN users over 512k links you may want to increase the size of the test file to for example 50kb. On the other hand if you have clients over very slow links, it may be better to stick with the current file size or even a smaller size.

Typically, the results of the new slow link detection method do not be greater than the maximum link speed of the connection. However, the results may not be reliable because of transient network conditions or other segment traffic. The Smsapm32.log file contains information about the size of the test file, its transfer time and the resulting link speed calculation.

The new test method also uses the current Slow Network Threshold Speed setting. Its default value remains at 40000 bps. You can locate this setting in the Site Control file and under the following registry key:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\SMS\Client\Sites\System\<Sitecode>\Client Components\Software Distribution

How to Configure Link Speed Detection in SMS 2.0 SP5

When you upgrade to SMS 2.0 SP5, the following registry values are set under the following registry key in the site server:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\SMS\Components\SMS_DISTRIBUTION_MANAGER

Slow Link Support Enabled=dword:00000000
Slow Link Test File Enabled=dword:00000000

By default, the link speed detection method remains as it has been with previous SMS SPs (Slow Link Support Enabled and Slow Link Test File Enabled set to 0).

To enable automatic support for the new slow link detection method, set both Slow Link Support Enabled and Slow Link Test File Enabled to 1. This directs Distribution Manager to copy the Netspeed.dat file from the SmsRootFolder\Bin\operating system directory to the root SMS package share or directory on the distribution point, \\server\smspkgX$, \\server\customshare or \\server\volume\smspkg, depending on the network operating system (NOS). In this mode, Distribution Manager updates the Netspeed.dat file on the distribution point if the copy in SmsRootFolder\Bin\operating system changes. If you want Distribution Manager to delete Netspeed.dat from the distribution point, set Slow Link Test File Enabled to 0 but leave Slow Link Support Enabled at 1.
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To permit manual copying and maintenance of the Netspeed.dat file on Distribution Points set Slow Link Support Enabled to 0 and Slow Link Test File Enabled to 1. In this mode, Distribution Manager does not copy or delete the Netspeed.dat file to or from a distribution point.

Important: Distribution Manager only performs its slow link support tasks when a distribution point is updated. If you have enabled SMS logging on the site server, you can verify Distribution Manager's current settings by searching the Distmgr.log file for the strings "Optional slow link speed" and "netspeed.dat").

On the client side, APM searches for the Netspeed.dat file on the distribution point beginning with the program's package directory and then working its way back up the path until it reaches either the share or the volume. This provides the SMS administrator the flexibility to specify how to perform the link test. For example, if you copy the Netspeed.dat file to the share, the slow link detection occurs the same way for all packages on that distribution point. However, if the Netspeed.dat file is only copied to the package directory, you can control the slow link detection on a per-package basis. You can also use a combination of the two methods. If you do so, some packages' directories have the file and their own link test control but others rely on the test control that you specified for all packages. You can use this level of control with automated support (both Slow Link Support Enabled and Slow Link Test File Enabled to 1) enabled because the Netspeed.dat file is only maintained at the distribution point level.

If APM does not find the Netspeed.dat file on the distribution point, it reverts to the pre-SP5 slow link detection method.

Note that the new detection method is only implemented in APM and not for the Slownet.exe or Slownet2.exe tools.
Modification Type:MinorLast Reviewed:6/14/2005
Keywords:kbSMS200preSP5fix kbSoftwareDist kbbug kbfix KB321310
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