LAN Manager Clients Cannot See Windows NT Computers (127789)

   S E R V P A C K
				

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Original Design

LAN Manager clients rely on server announcements that are broadcast over second class mailslots. The LAN Manager clients pickup server announcements and store them (for 1.5 times the announcement rate). If you run NET VIEW and the stored server announcement is still valid, the server name and server comments are displayed. If the next server announcement is not received by the client within 1.5 times the announcement rate, the server is dropped from the list. So if a client receives a server announcement at one minute intervals, it is likely to drop the server from the list if it does not receive another announcement in 1.5 minutes.

Here is a sample server announcement from USER1STA to LAN Manager clients:

   USER1STA *NETBIOS Multicast SMB C transact, File = \MAILSLOT\LANMAN
   NETBIOS: Datagram (0x08), USER1STA         -> USER1DOM       <00>

         -----

   NETBIOS: Destination Name = USER1DOM       <00>

       NETBIOS: SMB Name Type = Workstation (00)
       NETBIOS: Source Name = USER1STA
       NETBIOS: SMB Name Type = Server (20)
       NETBIOS: NetBIOS Data: Number of data bytes remaining = 115

   SMB: C transact, File = \MAILSLOT\LANMAN

      ------

   SMB: Command = C transact

      ------

   SMB: Mailslot class = Unreliable (broadcast)

           SMB: Byte count = 46
           SMB: Byte parameters
           SMB: Path name  = \MAILSLOT\LANMAN
           SMB: Transaction data
           SMB: Server announce opcode = Server announcement
           SMB: Service Flags Summary = 4097 (0x1001)
            SMB: .....................1 = Workstation service running
            SMB: ......................0. = Server service not available
           SMB: Major version = 3
           SMB: Minor version = 50
           SMB: Server announce rate = 720
           SMB: Computer name = USER1STA
           SMB: Server comment = User1's System;
				

NOTE: USER1STA sends a Multicast datagram to destination NetBIOS group name USER1DOM<00>. All LAN Manager clients post a NetBIOS Receive on their own domain, as well as other domains listed in their LANMAN.INI file, during initialization.

The server announce rate is set is seconds. Therefore, the server announce rate of 720 in the above example, it equates to 12 minutes. In Windows NT 3.1, the announce LAN Manager Server parameter in the registry could be used to set the announcement interval. However, in Windows NT workstation and Windows NT Server version 3.5, a new algorithm was developed. The server announcements are made during the start of the server service, and at the following approximate intervals:

   .5, 1, 1.5, 4, 8, 12, remain at 12 minutes].

For example:

   #  Time     Src         Description
   1  27.390   USER1STA    C transact, File = \MAILSLOT\LANMAN (30sec)
   2  50.303   USER1STA    C transact, File = \MAILSLOT\LANMAN (~20).
   3  79.151   USER1STA    C transact, File = \MAILSLOT\LANMAN (~30)
   4  348.700  USER1STA    C transact, File = \MAILSLOT\LANMAN (~260)
   5  861.290  USER1STA    C transact, File = \MAILSLOT\LANMAN (~520)
   6  1586.99  USER1STA    C transact, File = \MAILSLOT\LANMAN (~720)
   7  2312.10  USER1STA    C transact, File = \MAILSLOT\LANMAN (~720)
   8  3033.39  USER1STA    C transact, File = \MAILSLOT\LANMAN (~720)
   9  3758.56  USER1STA    C transact, File = \MAILSLOT\LANMAN (~720)
				

The announce parameter is ignored.

As a result, you may not see Windows NT workstation and server names when you run NET VIEW on LAN Manager clients, right after you boot the computer. The longest wait time, if you just miss a server announcement, would be 12 minutes. Once you receive the server announcement, it is valid for 18 minutes.

New Design

The default initial announce frequency for LAN Manager clients is now four minutes, and increases to once every 12 minutes.

The AnnDelta delta parameter, although adjustable, defaults to 3000 milliseconds. This parameter specifies the time by which the announcement period can vary. This helps to prevent several servers from continuously announcing simultaneously, thereby reducing network load peaks.