DOCUMENT:Q297040 08-MAY-2002 [winnt] TITLE :Windows May Hang When Attempting to Establish a TCP Connection PRODUCT :Microsoft Windows NT PROD/VER::4.0,4.0 SP6,4.0 SP6a OPER/SYS: KEYWORDS: ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft Windows NT Server versions 4.0, 4.0 SP6a - Microsoft Windows NT Server versions 4.0, 4.0 SP6, Terminal Server Edition ------------------------------------------------------------------------------- SYMPTOMS ======== A Windows NT 4.0-based server with a recent post-SP6a hotfix, or a Windows NT 4.0 Terminal Server with a recent post-SP6 hotfix, may stop responding (hang) if it attempts to make a TCP connection with an IP address that is nonexistent. For example, if a Windows NT 4.0-based server with an address of 129.68.72.10 attempts to connect by using Telnet to an address of 129.68.72.40, and that address is either nonexistent or unavailable, the server may hang. This is a "hard" hang with no mouse control and no CTRL+ALT+DELETE functionality available. The server is unresponsive from the console and cannot be pinged on the network. For this hang to occur, the TCP/IP SynAttackProtect registry value must be set. For additional information about this registry entry, click the article number below to view the article in the Microsoft Knowledge Base: Q142641 Internet Server Unavailable Because of Malicious SYN Attacks CAUSE ===== Under certain circumstances, the spinlock for the TCP/IP connection table lock is acquired but not released; this causes the server to hang. RESOLUTION ========== A supported fix is now available from Microsoft, but it is only intended to correct the problem described in this article and should be applied only to systems experiencing this specific problem. To resolve this problem, contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information on support costs, please go to the following address on the World Wide Web: http://support.microsoft.com/default.aspx?scid=fh;EN-US;CNTACTMS NOTE: In special cases, charges that are normally incurred for support calls may be canceled, if a Microsoft Support Professional determines that a specific update will resolve your problem. Normal support costs will apply to additional support questions and issues that do not qualify for the specific update in question. The English version of this fix should have the following file attributes or later: Date Time Size File name -------------------------------------- 27-Apr-2001 15:54 174,896 Tcpip.sys NOTE: Because of file dependencies, this hotfix requires Microsoft Windows NT 4.0 Service Pack 6a. STATUS ====== Microsoft has confirmed this to be a problem in the Microsoft products that are listed at the beginning of this article. Additional query words: freeze lock lockup ====================================================================== Keywords : Technology : kbWinNTsearch kbWinNT400search kbWinNTSsearch kbWinNTS400sp6 kbWinNTS400search kbWinNTS400 kbNTTermServ400 kbNTTermServ400sp6 kbNTTermServSearch Version : :4.0,4.0 SP6,4.0 SP6a Hardware : ALPHA x86 Issue type : kbbug Solution Type : kbfix ============================================================================= 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. Copyright Microsoft Corporation 2002.