Multiple Data Centers and the Window Mechanism

The Sun OpenDS Standard Edition directory server provides a window mechanism which specifies that a certain number of update requests are sent without one server having to wait for an acknowledgement from the recipient server before continuing.

The window size represents the maximum number of update messages that can be sent without immediate acknowledgement from the recipient server. If the topology spans multiple data centers connected by a network with large latency, it might be worth increasing the window size beyond its default value of 100. To assess whether the window size is the limiting factor in replication thoughput, monitor the current-send-window and current-rcv-window attributes below cn=monitor.

If a server publishes a current-send-window to another server that is consistently zero or close to zero and the corresponding server publishes a current-rcv-window that is higher, it means that all the data are currently in the network. In this case, increasing the window size on the recipient server should increase replication speed and reduce replication delay. These improvements will result in the consumption of more resources on the recipient server.