RAS Server Fails to Autodisconnect Inactive RAS Clients With TCP

• Microsoft Windows NT Workstation versions 3.5 and 3.51
• Microsoft Windows NT Server versions 3.5 and 3.51

SYMPTOMS

Your Windows NT Remote Access (RAS) Server fails to disconnect idle RAS clients that have dialed in using the TCP/IP protocol or a combination of the TCP/IP protocol with IPX or NetBEUI.

CAUSE

When the TCP/IP protocol is used over the RAS connection, a Host Announcement from the RAS client causes the RAS server to reset the RAS Autodisconnect timer.

On a Windows NT machine, the Announce parameter defaults to 720 seconds (or 12 minutes). On a Windows NT RAS server, the RAS Autodisconnect parameter defaults to 20 minutes. If your RAS client is also a Windows NT machine, the RAS Autodisconnect timer will reset every 12 minutes, and therefore, the RAS client will never timeout.

If you do not use the TCP/IP protocol over the RAS connection, a Host Announcement from the RAS client will not cause the RAS Autodisconnect parameter to reset.

By design, the RAS Autodisconnect parameter sets the time interval after which inactive connections are terminated. This inactivity is measured by lack of NetBIOS session data transfer. A Host Announcement is not considered NetBIOS session activity.

RESOLUTION

Configure the value of the RAS Autodisconnect parameter so that it is less than the value of the Announce parameter (which specifies the interval of time that a server uses between sending out a Host Announcement).

WARNING: Using the Registry Editor incorrectly can cause serious, system- wide problems that may require you to reinstall Windows NT to correct them. Microsoft cannot guarantee that any problems resulting from the use of the Registry Editor can be solved. Use this tool at your own risk.

The Announce parameter can be configured via the following Registry parameter:

   HKEY_LOCAL_MACHINE\SYSTEM
      \CurrentControlSet\Services\LanmanServer\parameters

         Announce   REG_DWORD   1 to 65535 seconds, Default: 720

   HKEY_LOCAL_MACHINE\SYSTEM
      \CurrentControlSet\Services\RemoteAccess\parameters

         Autodisconnect   REG_DWORD   0 to 1000 minutes, Default: 20

STATUS

Microsoft has confirmed this to be a problem in Windows NT version 3.51. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.