diff --git a/docs/reference/modules/discovery/zen.asciidoc b/docs/reference/modules/discovery/zen.asciidoc
index 02282d78449..64281d93950 100644
--- a/docs/reference/modules/discovery/zen.asciidoc
+++ b/docs/reference/modules/discovery/zen.asciidoc
@@ -146,3 +146,16 @@ Note, it can still be enabled, with disabled internal multicast
 discovery, but still have external discovery working by keeping
 `discovery.zen.ping.multicast.enabled` set to `true` (the default), but,
 setting `discovery.zen.ping.multicast.ping.enabled` to `false`.
+
+[float]
+==== Cluster state updates
+
+The master node is the only node in a cluster that can make changes to the
+cluster state. The master node processes one cluster state update at a time,
+applies the required changes and publishes the updated cluster state to all
+the other nodes in the cluster. Each node receives the publish message,
+updates its own cluster state and replies to the master node, which waits for
+all nodes to respond, up to a timeout, before going ahead processing the next
+updates in the queue. The `discovery.zen.publish_timeout` is set by default
+to 30 seconds and can be changed dynamically through the
+<<cluster-update-settings,cluster update settings api>>.