Microsoft KB Archive/276045

= Telnet IP+DM Is Ignored If TN3270 Server Is Already Queuing Data =

Article ID: 276045

Article Last Modified on 2/22/2007

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APPLIES TO


 * Microsoft SNA Server 4.0
 * Microsoft SNA Server 3.0 Service Pack 2
 * Microsoft SNA Server 3.0 Service Pack 3
 * Microsoft SNA Server 3.0 Service Pack 4
 * Microsoft SNA Server 4.0
 * Microsoft SNA Server 4.0 Service Pack 1
 * Microsoft SNA Server 4.0 Service Pack 2
 * Microsoft SNA Server 4.0 Service Pack 3
 * Microsoft Host Integration Server 2000 Standard Edition

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This article was previously published under Q276045



IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:

256986 Description of the Microsoft Windows Registry



SYMPTOMS
If you use the Rumba TN3270 client, the emulator may stop responding (hang) when it is used with the TN3270 Server to access a host application.

If a network analysis tool, such as Microsoft Network Monitor, is used to capture a network trace of the TCPIP traffic between the TN3270 client and TN3270 Server, this problem may occur after the client sends an Interrupt Process (IP) and Data Mark (DM) message sequence (FFF4FFF2) in the inbound data stream.

Network Monitor frame illustration:

+ Frame: Base frame properties

+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:DOD Internet Protocol

+ IP: ID = 0x7CC1; Proto = TCP; Len: 44

TCP: .AP..., len: 4, seq:60113-60117, ack: 84013, win: 7744, src: 1097 dst: 23 (TELNET)

TCP: Source Port = 0x0449

TCP: Destination Port = Telnet

TCP: Sequence Number = 60113 (0xEAD1)

TCP: Acknowledgement Number = 84013(0x1482D)

TCP: Data Offset = 20 (0x14)

TCP: Reserved = 0 (0x0000)

TCP: Flags = 0x18 : .AP...

TCP: ..0..... = No urgent data

TCP: ...1.... = Acknowledgementfield significant

TCP: ....1... = Push function

TCP: .....0.. = No Reset

TCP: ......0. = No Synchronize

TCP: .......0 = No Fin

TCP: Window = 7744 (0x1E40)

TCP: Checksum = 0x7502

TCP: Urgent Pointer = 0 (0x0)

TCP: Data: Number of data bytes remaining = 4 (0x0004)

TELNET: To Server From Port = 1097

TELNET: Telnet Command = IAC IP(INTERRUPT PROCESS)

TELNET: Telnet Command = IAC DM (DATA MARK)

00000: 00 00 0C 07 AC 02 00 C0 4F 61 6B 94 08 00 45 10

00010: 00 2C 7C C1 40 00 80 06 98 BC 9D CB A3 8C 9D CB

00020: 06 1B 04 49 00 17 00 00 EA D1 00 01 48 2D 50 18

00030: 1E 40 75 02 00 00 FF F4 FF F2



CAUSE
The problem is that TN3270 client emulators can send data or, as in this case, a function key (PA1 key), when the client does not have direction on the session flow.

To enable TN3270 clients to work in this manner and to avoid a TN3270 session protocol violation error, SNA Server internally queues such data until the client is granted direction on the session and can legitimately send inbound data.

In this instance, however, after the client's illegal PA1 key is queued, the TN3270 Server subsequently fails to process the following IP-DM sequence. This is because the TN3270 Server adds it to the queue of data for later inbound transmission to the host when the client is granted direction on the session flow. As a result, no SIGNAL is sent, which typically is expected when an IP command is processed.



SNA Server 4.0
To resolve this problem, obtain the latest service pack for SNA Server 4.0. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

215838 How to Obtain the Latest SNA Server Version 4.0 Service Pack

Host Integration Server 2000
To resolve this problem, obtain the latest service pack for Host Integration Server 2000. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

328152 How to Obtain the Latest Host Integration Server 2000 Service Pack



STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article. This problem was first corrected in Host Integration Server 2000 Service Pack 1. This problem was first corrected in SNA Server 4.0 Service Pack 4.



MORE INFORMATION
The TN3270 Server has been enhanced so that it no longer tries to act as a broker to resolve protocol ambiguities between the TN3270 client and host. The DisableDataQueuing registry option, which turns off queuing of data by the TN3270 Server, has been implemented as follows:

WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

 Start Registry Editor (Regedt32.exe). Locate the following key in the registry:

HKEY_LOCAL_MACHINE\System\CCS\Services\TN3270\Parameters

NOTE: This registry key is one path; it has been wrapped for readability.

 On the Edit menu, click Add Value, and then add the following registry value:

Value Name: DisableDataQueuing

Data Type: REG_SZ

Value: YES

 Quit Registry Editor.</ol>

This registry option is a generic solution to problems that are caused by clients that are not working correctly (sending data when they don't have direction) and/or hosts that are not working correctly (failing to lock the client's keyboard appropriately through the WCC byte).

Additional query words: sp1 sp2 sp3 HIS 2000

Keywords: kbbug kbfix kbsna400presp4fix kbhostintegserv2000sp1fix kbhostintegserv2000presp1fix kbsna400sp4fix KB276045

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