diff --git a/core/store/dist/src/main/java/org/onlab/onos/store/cluster/messaging/MessageSubject.java b/core/store/dist/src/main/java/org/onlab/onos/store/cluster/messaging/MessageSubject.java
new file mode 100644
index 0000000..3b888b3
--- /dev/null
+++ b/core/store/dist/src/main/java/org/onlab/onos/store/cluster/messaging/MessageSubject.java
@@ -0,0 +1,14 @@
+package org.onlab.onos.store.cluster.messaging;
+
+/**
+ * Representation of a message subject.
+ */
+public enum MessageSubject {
+
+    /** Represents a first greeting message. */
+    HELLO,
+
+    /** Signifies a heart-beat message. */
+    ECHO
+
+}