WFW Direct Hosting over ODI Drivers Drop Network Connections

Last reviewed: September 9, 1996
Article ID: Q140007

The information in this article applies to:

Microsoft Windows NT Workstation versions 3.5 and 3.51
Microsoft Windows NT Server versions 3.5 and 3.51
Microsoft Windows for Workgroups version 3.11

SUMMARY

A Windows for Workgroups 3.11 client, running IPX and connecting to an Windows NT version 3.5 or 3.51 Server or Workstation by default uses direct hosting. Direct hosting is a method of bypassing the NetBIOS layer and sending client/server messages (SMBs) directly over the transport, in this case, IPX.

If the Windows for Workgroups 3.11 client is using an Open Datalink Interface (ODI) driver rather than an NDIS driver, the client may drop packets from the server and lose the connection.

This is most evident where you have large file reads and a fast server.

MORE INFORMATION

You may be able to improve the connection reliability by not using direct hosting from client to server. This forces NetBIOS to manage the session, rather than making the redirector manage retransmissions. To turn direct hosting off at the client, add the following parameter to the [network] section of system.ini:

   directhost=no

Note: Page 4-12 of the "Windows for Workgroups Resource Kit", Addendum for Version 3.11 incorrectly states this parameter as 'directhosting'. This is a documentation error.

Additionally, you must install the IPX/SPX Compatible Transport with NetBIOS on the Windows for Workgroups client.

When you turn direct hosting off, large file read requests from the client are requested in a read block raw SMB, and the data is transferred over the NetBIOS session. The following trace shows at frame 20, the client initiates a read block raw, and the data is returned by the server over the NetBIOS session:

#    DeltaT  Src MAC     Dst MAC   Protocol Description

20   0.004   WFW Client  NT server   SMB     C read block raw, FID = 0x800,
                                                Read 0xfe00 at
21   0.147   NT server   WFW Client  NBIPX   Session Data
22   0.001   NT server   WFW Client  NBIPX   Session Data, Send Seq 0x0C,
                                                Offset 0x5AC
23   0.002   WFW Client  NT server   NBIPX   Session Data, Ack, Recv Seq
                                                0x0D, 0x10 Bytes Received
24   0.002   NT server   WFW Client  NBIPX   Session Data
25   0.002   NT server   WFW Client  NBIPX   Session Data
26   0.001   NT server   WFW Client  NBIPX   Session Data, Send Seq 0x0F,
                                                Offset 0x16B0
27   0.002   WFW Client  NT server   NBIPX   Session Data, Ack, Recv Seq
                                                0x10, 0x13 Bytes Received

If direct hosting is on, then the redirector initiates a read block multiplex, and the data is sent back in read block multiplex response SMBs, directly over IPX. The following trace shows a read block multiplex coming from the client at frame 19. Frames 20 through 29 show the server responding with read block multiplex responses, and frame 30 is another read block multiplex command from the client:

#    DeltaT  Src MAC     Dst MAC   Protocol Description

19   0.005   WFW Client  NT server    SMB   C read block mpx, FID = 0x800,
                                               Read 0x3750 at 0x00000000
20   0.003   NT server   WFW Client   SMB   R read block mpx, Read 0x588 of
                                               0x3750
21   0.006   NT server   WFW Client   SMB   R read block mpx, Read 0x588 of
                                               0x3750
22   0.001   NT server   WFW Client   SMB   R read block mpx, Read 0x588 of
                                               0x3750
23   0.002   NT server   WFW Client   SMB   R read block mpx, Read 0x588 of
                                               0x3750
24   0.002   NT server   WFW Client   SMB   R read block mpx, Read 0x588 of
                                               0x3750
25   0.001   NT server   WFW Client   SMB   R read block mpx, Read 0x588 of
                                               0x3750
26   0.001   NT server   WFW Client   SMB   R read block mpx, Read 0x588 of
                                               0x3750
27   0.002   NT server   WFW Client   SMB   R read block mpx, Read 0x588 of
                                               0x3750
28   0.001   NT server   WFW Client   SMB   R read block mpx, Read 0x588 of
                                               0x3750
29   0.001   NT server   WFW Client   SMB   R read block mpx, Read 0x588 of
                                               0x3750
30   0.004   WFW Client  NT server    SMB   C read block mpx, FID = 0x800,
                                               Read 0x3750 at 0x00003750

In this case, the redirector is responsible for requesting resends of lost packets in either direction. This may be too much of a burden on the Windows for Workgroups redirector which is running over an ODI driver. The extra layer needed to map NDIS 3.0 protocols to an ODI NIC driver (MSODISUP.386) may also contribute to the problem, as running direct hosting over NDIS drivers does not seem to exhibit this problem.

KBCategory: kbnetwork
KBSubcategory: ntinterop
Additional reference words: prodnt 3.11 3.50 3.51 directhost directhosting

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.

Last reviewed: September 9, 1996
© 1998 Microsoft Corporation. All rights reserved. Terms of Use.