DOCUMENT:Q232997 10-AUG-2001 [winnt] TITLE :Convergence in Windows NT Load Balancing Service PRODUCT :Microsoft Windows NT PROD/VER:winnt:1.0,4.0 OPER/SYS: KEYWORDS:kbnetwork ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft Windows NT Server, Enterprise Edition version 4.0 - Microsoft Windows NT Load Balancing Service 1.0 ------------------------------------------------------------------------------- SUMMARY ======= Each server in a Windows NT Load Balancing Service (WLBS) cluster receives all inbound requests to the Virtual IP Address (VIP). Convergence is the process in which the servers (through a proprietary hashing algorithm) agree in advance which server handles a given request. The decision is made based on the packet's source IP address and possibly TCP or UDP port number (if Affinity is not used). MORE INFORMATION ================ WLBS balances load in a statistical manner; all of the client IP:port space is mapped to the servers as a consequence of the convergence process. Each server is assigned parts of this space in order to achieve load distribution. The convergence process is started when servers are added to or removed from a cluster. Cluster integrity is monitored by the periodic exchange of heartbeats between cluster members. When a member misses a user-defined number of heartbeats from a server, it initiates the convergence process to form a new cluster. When a new server is added to the cluster, the existing servers detect the heartbeat from the new server and the convergence process is initiated. The convergence process takes approximately three seconds, and cluster operations continue during this time. Convergence is complete when all present hosts exchange consistent information and a sufficient number of status messages are exchanged. REFERENCES ========== For more information about Cluster Server and WLBS, please see the following Microsoft Knowledge Base article: Q232711 How Cluster Integrity is Monitored in WLBS Additional query words: ====================================================================== Keywords : kbnetwork Technology : kbWinNTsearch kbWinNT400search kbWinNTSsearch kbWinNTSEntSearch kbWinNTSEnt400 kbWinNTS400search kbWinNTLBS100 kbWinNTLBSSearch Version : winnt:1.0,4.0 Issue type : kbinfo ============================================================================= 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 2001.