Virtual Circuit Error 3193

This article was previously published under Q109555

In a mixed Microsoft NT Advanced Server environment with LAN Manager 2.x and OS/2 1.3, where LAN Manager is the Backup Domain Controller to an Advanced Server Primary Domain Controller, the following error message appears in the error log of the Backup Domain Controller:

   WORKSTATION         3193                11-30-93 08:59pm
   NET3193:  A virtual circuit error occurred on the session to NTSERVER

     The NCB command and return code is the data.
       96 18
		

This is caused by the Advanced Server parameter Autodisconnect. When an Advanced Server machine Autodisconnects a session, it sends an NBFP Session.End frame with the DATA2 flag (termination indicator) set to 0001 (abnormal) rather than 0000 (normal).

This problem does not occur on LAN Manager OS/2 Primary Domain Controllers. The LAN Manager OS/2 Primary Domain Controller sends a Session.End frame with DATA2 set to 0000.



This Session.End frame is transmitted as a result of a HANG.UP command, a SEND command that timed out, or some abnormal condition.

DATA2 contains the Termination indicator. This two-byte field is used to indicate the type of termination, where X'0000' indicates a normal session end (as a result of a HANG.UP command) and X'0001' indicates an abnormal session end (typically a SEND command has timed out).

The following is an example of an Autodisconnect from an Advanced Server machine disconnecting a session created on the OS/2 BDC.

Frame   Time          MAC Source    MAC Dest Protocol Description
58      321.045       LCSCOTTSU3    FATMON   NETBIOS  Session End (0x18)

+ ETHERNET: 802.3 Length = 60
+ LLC: C I-FRAME N(S) = 0x04, N(R) = 0x0E POLL
  NETBIOS: Session End (0x18)

      NETBIOS: Length = 14 (0x000E)
      NETBIOS: Signature = 0xEFFF
      NETBIOS: Command = Session End (0x18)
      NETBIOS: Data2 = 0x0001 (abnormal<<<This is the Termination
      Indicator.
      NETBIOS: Destination Number = 0x21
      NETBIOS: Source Number = 0x03
      NETBIOS: NetBIOS Data: Number of data bytes remaining = 28 (0x001C)

00000:  00 DD 01 0F C3 C8 00 DD 01 0F C2 DA 00 12 F0 F0   ................
00010:  08 1D 0E 00 FF EF 18 00 01 00 00 00 00 00 21 03   ..............!.
00020:  53 52 56 30 31 20 20 20 20 20 20 20 00 4C 43 53   SRV01       .LCS
00030:  43 4F 54 54 53 55 33 20 20 20 20 20               COTTSU3
		

For more information, see pages 5-31 of the IBM "Local Area Network Technical Reference."