Convergence in Windows NT Load Balancing Service

• Microsoft Windows NT Server, Enterprise Edition version 4.0
• 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
Version : winnt:1.0,4.0
Platform : winnt
Issue type : kbinfo