LAN Manager Redirector Sends Extra Second Class Mailslot

ID: Q113223

The information in this article applies to:

Microsoft LAN Manager, version 2.2b

SYMPTOMS

With LAN Manager 2.2b, second class mailslot traffic doubles. An example of a second class mailslot is \MAILSLOT\NET\NETLOGON which is generated when a Microsoft LAN Manager MS-DOS client attempts to logon to the network.

CAUSE

Second class mailslots were being sent to two NetBIOS groupname destinations:


      "<DOMAIN><PAD>\0x00"
      "<DOMAIN><PAD>\0x1c"

where, <DOMAIN> is the Workstation Domain, and <PAD> is space padding.

NetBIOS names are 16 bytes long. The last byte of Microsoft NetBIOS names typically implies a destination class. An extension of \0x00 (a single character of ASCII value 0) implies a workstation name. An extension of \0x1c (a single character of ASCII value 1c hex) implies a Microsoft Windows NT domain controller (or Internet Group Name).

Code was added to Microsoft LAN Manager 2.2b to send second class mailslots to the \0x1c NetBIOS name as well as to the \0x00 NetBIOS name.

RESOLUTION

Code was removed from NETWKSTA.EXE to prevent this unnecessary mailslot broadcast. The \0x1c name is useful only when attempting to logon to Microsoft Windows NT domain controllers with TCP/IP protocol. Logon attempts with \0x00 (standard NetBIOS groupname destination) are sufficient, even to Windows NT domain controllers; the \0x1c destination is unnecessary.

STATUS

Microsoft has confirmed this to be a problem in LAN Manager version 2.2b. A fix to this problem is in development, but has not been regression-tested and may be destabilizing in production environments. Microsoft does not recommend implementing this fix at this time. Contact Microsoft Product Support Services for more information on the availability of this fix.

Additional query words: 3.10 mailslot redir netwksta

Keywords :
Version : :2.2b
Platform :
Issue type :