SMS: Slownet Determines Network Speed at Logon

Slownet.exe is called at logon in SMSLS to determine the network connection speed between the client and the logon point. Depending on the client platform, the file to which Slownet maps can be any of the following files: Slownet's calculation of connection speed is a snapshot that varies substantially depending on a number of factors including, but not limited to, maximum connection speed, line quality, and current network load. The Windows 32 Slownet.exe uses the Win32 MultinetGetConnectionPerformance API call. This API calls asks the transport layer (for example, IP) to tell it how fast the connection is. SMS does not have any control over the return value from this API call. It could report a significantly slower speed than the actual connection, which can frequently be attributed to a slow network (not just a slow RAS connection).

If Slownet detects that a connection speed is less than 40 KB, the client installation routine is bypassed and the client is not installed.

Slownet can be used for the following tasks:

• Determining the connection speed between a client and its server
• Prompting the user to continue with the client installation despite a slow network connection being detected
• Detecting whether the client is logging on to the network over RAS and bypassing the client installation if RAS is detected at all (similar to the Checkras utility's functionality)

In some circumstances, you may want to change the default threshold that Slownet uses to determine whether or not a client will be installed. If the threshold is lowered, keep in mind that the client installation may take a long time and may cause the user to wait at logon for components to be installed or upgraded.

If it is necessary to force clients to install over a slow link, consider the following options:

• Changing the threshold speed specified in the logon script
• Customizing the logon script to prompt the user whether or not to run the SMS client installation (after determining it is a slow link)
• Removing all references to the Slownet.exe and Snboot.exe calls from the logon script
• Adding a custom determination in the logon script (for example, "Is this user a member of the 'remote salespeople' group and therefore should always run SMS")
• Using the Systems Management Installation wizard (Smsman.exe)
• Using alternate discovery and installation methods such as Network Discovery or Windows NT Remote Client Installation

To determine exactly what Slownet is doing, you can run Slownet with the /v parameter to print verbose output to the screen.

Manually Determining the Connection with Slownet

You can use Slownet as a command-line utility on the client computer. If the Slownet.exe file is not already on the client, copy the appropriate Slwntxx.exe file to the client computer. Run the following command at a command prompt: For example: This command reports your calculated speed and tells you if your link is faster or slower than 10 Kbps.

To determine if the calculated speed is faster or slower than 40 Kbps (by default, Slownet detects for at least 40 Kbps), run the following command from a command prompt: Note that if the server or share is not available, Slownet assumes a fast link and returns the following message:

Modifing Slownet in the SMSLS Logon Script

If you want to modify the Slownet threshold, back up the Ssmsls.bat file in the Sms\Data\Nt_logon folder to Smsls.org. Then, modify the following lines in the Sms\Data\Nt_logon directory\Smsls.bat file:

• :OK_TO_PROCEED
  Replace: %SMS_LOCAL_DIR%\MS\SMS\CORE\BIN\Slownet.exe %0
  With: %SMS_LOCAL_DIR%\MS\SMS\CORE\BIN\Slownet.exe %0 1000
• :SLOWNETUSER
  Replace: %SMS_LOCAL_DIR_USER%\MS\SMS\CORE\BIN\Slownet.exe %0
  With: %SMS_LOCAL_DIR_USER%\MS\SMS\CORE\BIN\Slownet.exe %0 1000
• :SLOWNETTEMP
  Replace: %TEMP%\Slownet.exe %0
  With: %TEMP%\Slownet.exe %0 1000
• :SLOWNETSERVER
  Replace: %0\..\SNBOOT.exe
  With: %0\..\SNBOOT.exe 1000

NOTE: The server and share names must be in all lowercase letters. This example presumes a minimal connection speed of 1000 bps, but this value can be any value less than 40,000.

If the Smsls.bat file is changed after the creation of the logon point, copy the updated Smsls.bat file to the %Windir%\System32\Repl\Export\Scripts and %Windir%\System32\Repl\Import\Scripts folders on the logon server.

Slownet with RAS

When you dial in over RAS, the speed Slownet detects may be lower than the dial-up status indicator, as indicated in the following table.
When a RAS client runs the SMSLS batch file at logon, Slownet.exe is copied to the client and run. If it detects that the connection speed is slower than 40 KB, the client is not installed.

It is possible to use Slownet to only determine whether a client is using a RAS connection. To do so, substitute the connection speed with 0. For example: If RAS is detected, the return code is 0.

If you want to prevent the client from having any files (including Slownet) installed at logon, you can use the Checkras utility included in the BackOffice Resource Kit. Checkras.exe checks for RAS connections on the client instead of trying to determine the link speed. You can use the Checkras.exe utility in your logon script to determine whether or not a user is connected by a RAS connection, and then include commands in your logon script based on the results returned by Checkras.exe.

The following sample Windows NT domain logon script uses Checkras.exe: NOTE: Windows NT 3.51 clients are not supported with Systems Management Server 2.0 over RAS. If Windows NT 3.51 clients will be logging in over RAS, Checkras must be used to prevent them from installing the SMS client.

For additional information about client installation, click the article number below to view the article in the Microsoft Knowledge Base: