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Q175321: SNA Client Sessions Hang Until SNA Server Is Restarted

Article: Q175321
Product(s): Microsoft Windows NT
Version(s): WINDOWS:2.11,2.11SP1,2.11SP2,3.0,3.0SP1,3.0SP2; winnt:3.51,4.0
Operating System(s): 
Keyword(s): kbinterop kbnetwork kbWinNT400sp4fix kbDriver
Last Modified: 09-AUG-2001

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The information in this article applies to:

- Microsoft Windows NT Server versions 3.51, 4.0 
- Microsoft SNA Server, versions 2.11, 2.11 SP1, 2.11 SP2, 3.0, 3.0 SP1, 3.0 SP2 
- Microsoft Windows NT Server version 4.0, Terminal Server Edition 
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SYMPTOMS
========

When connecting SNA Server to a host system over 802.2 through an IBM 3174
(though this does not require a 3174 to occur), all SNA clients suddenly stop
receiving any responses to user requests. If 3270 emulation is being used, 3270
users may get stuck in a perpetual XCLOCK state and never receive a host
response. This problem may also occur with TN3270 clients that connect through
the SNA Server TN3270 server.

CAUSE
=====

A portion of the problem was related to a previous Windows NT Dlc.sys problem.
For additional information, please see the following article in the Microsoft
Knowledge Base:

ARTICLE-ID: Q168662
TITLE : DLC May Fail When Connecting Through an IBM 2210 Router


RESOLUTION
==========

Windows NT 3.51
---------------

The Windows NT 3.51 fix should have the following time stamp:

+-----------------------------------------------+
| 10/29/97 | 04:23p | 58,192  | Dlc.sys | Intel | 
+-----------------------------------------------+
| 10/29/97 | 04:21p | 100,752 | Dlc.sys | Alpha | 
+-----------------------------------------------+
| 10/29/97 | 04:20p | 88,016  | Dlc.sys | MIPS  | 
+-----------------------------------------------+

Windows NT 4.0
--------------

To resolve this problem, obtain the latest service pack for Windows NT 4.0 or
Windows NT Server 4.0, Terminal Server Edition. For additional information,
please see the following article in the Microsoft Knowledge Base:

  Q152734 How to Obtain the Latest Windows NT 4.0 Service Pack


STATUS
======

Microsoft has confirmed this to be a problem in Windows NT version 3.51. A
supported fix is now available, but has not been fully regression tested and
should be applied only to systems experiencing this specific problem. Unless you
are severely impacted by this specific problem, Microsoft recommends that you
wait for the next service pack that contains this fix. Contact Microsoft
Technical Support for more information.


Microsoft has confirmed this to be a problem in Windows NT 4.0 and Windows NT
Server 4.0, Terminal Server Edition. This problem was first corrected in Windows
NT 4.0 Service Pack 4.0 and Windows NT Server 4.0, Terminal Server Edition
Service Pack 4.


MORE INFORMATION
================

This problem has been observed when using SNA Server on top of Windows NT 4.0
Service Pack 3 Dlc.sys driver, although it may occur with previous Windows NT
4.0 service pack levels and also with Windows NT 3.51. If the SNA Server is
stopped and restarted, the 802.2 connection stays in a Pending state and does
not reactivate. The only way to recover the 802.2 connection is to restart the
server running both Windows NT and SNA Server.

SNA Server 802.2 link service Level 2 traces will show that the link service has
several outstanding calls to the Windows NT Dlc.sys TRANSMIT.I.FRAME function
that never complete. A network monitor LAN trace shows that Windows NT stops
sending any DLC I-frames to the remote SNA system, although I-frames continue to
be accepted from the remote system. The problem starts to occur after Windows NT
DLC receives a REJ response to a retransmitted I-frame. The following network
monitor trace illustrates the problem:

Src Addr  Dst Addr  Description
--------  --------  -----------

SNASRV    HOST      I DSAP=0x04 SSAP=0x04 C N(S) = 0x0B, N(R) = 0x10
SNASRV    HOST      I DSAP=0x04 SSAP=0x04 C N(S) = 0x0C, N(R) = 0x10 POLL
HOST      SNASRV    RR DSAP=0x04 SSAP=0x05 R N(R) = 0x0B FINAL
SNASRV    HOST      I DSAP=0x04 SSAP=0x04 C N(S) = 0x0B, N(R) = 0x10 POLL
HOST      SNASRV    I DSAP=0x04 SSAP=0x04 C N(S) = 0x10, N(R) = 0x0B
HOST      SNASRV    I DSAP=0x04 SSAP=0x04 C N(S) = 0x11, N(R) = 0x0B
SNASRV    HOST      RR DSAP=0x04 SSAP=0x05 R N(R) = 0x11
HOST      SNASRV    I DSAP=0x04 SSAP=0x04 C N(S) = 0x12, N(R) = 0x0B
HOST      SNASRV    RR DSAP=0x04 SSAP=0x05 R N(R) = 0x0C
SNASRV    HOST      RR DSAP=0x04 SSAP=0x05 R N(R) = 0x13
HOST      SNASRV    RR DSAP=0x04 SSAP=0x05 R N(R) = 0x0D FINAL
HOST      SNASRV    REJ DSAP=0x04 SSAP=0x05 R N(R) = 0x0D FINAL
HOST      SNASRV    I DSAP=0x04 SSAP=0x04 C N(S) = 0x13, N(R) = 0x0D
HOST      SNASRV    I DSAP=0x04 SSAP=0x04 C N(S) = 0x14, N(R) = 0x0D
SNASRV    HOST      RR DSAP=0x04 SSAP=0x05 R N(R) = 0x15
HOST      SNASRV    I DSAP=0x04 SSAP=0x04 C N(S) = 0x15, N(R) = 0x0D
SNASRV    HOST      RR DSAP=0x04 SSAP=0x05 R N(R) = 0x16
SNASRV    HOST      RR DSAP=0x04 SSAP=0x04 C N(R) = 0x16 POLL

In the above trace, Windows NT (SNASRV) sends I-frames 0x0B and 0x0C, setting the
POLL bit after sending I-frame 0x0C. The host does not ack these I-frames,
causing Windows NT (SNASRV) to resend I-frame 0x0B in line 4 above. The host
eventually acks the I-frame 0x0C, but it then REJects the resend of I-frame
0x0B. After Windows NT DLC receives the host REJ (to the retransmitted I-frame
0x0B), Windows NT DLC never sends any more I-frames to the host. As this occurs,
the SNA Server 802.2 link service's calls to TRANSMIT.I.FRAME stop responding
(hang) and never complete.

Additional query words:

======================================================================
Keywords          : kbinterop kbnetwork kbWinNT400sp4fix kbDriver 
Technology        : kbWinNTsearch kbWinNT351search kbWinNT400search kbWinNTSsearch kbWinNTS400search kbWinNTS400 kbWinNTS351 kbNTTermServ400 kbNTTermServSearch kbWinNTS351search kbAudDeveloper kbSNAServSearch kbSNAServ300 kbSNAServ211 kbSNAServ211SP1 kbSNAServ211SP2 kbSNAServ300SP1 kbSNAServ300SP2
Version           : WINDOWS:2.11,2.11SP1,2.11SP2,3.0,3.0SP1,3.0SP2; winnt:3.51,4.0
Issue type        : kbbug
Solution Type     : kbfix

=============================================================================

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