Replication communication uses a proprietary binary protocol that implements on top of the TCP/IP protocol using SSL encryption. Some protocol messages are used for administrative purposes, such as WAN Gateway server negotiation or flow control, some carry updates to replicated data, and others are directed to all servers for monitoring requests.

In a replicated topology, each participating Directory Server connects to every other server through the replication server port to monitor health. Servers that share the same location setting are connected to rapidly replicate changes, and the WAN Gateway servers are all interconnected to replicate changes across locations.

The Directory Servers keep connections open as long as possible to reduce the communication latency when exchanging messages. Heartbeat messages transmit on a regular basis to detect a network failure or an unresponsive directory server as early as possible. Heartbeat messages also prevent idle connections from being closed by firewalls.

Replication Communication Flow