diff --git a/core/api/src/main/java/org/onlab/onos/net/flow/Treatment.java b/core/api/src/main/java/org/onlab/onos/net/flow/Treatment.java
new file mode 100644
index 0000000..8318b66
--- /dev/null
+++ b/core/api/src/main/java/org/onlab/onos/net/flow/Treatment.java
@@ -0,0 +1,21 @@
+package org.onlab.onos.net.flow;
+
+import org.onlab.onos.net.PortNumber;
+
+/**
+ * Abstraction of different kinds of treatment that can be applied to an
+ * outbound packet.
+ */
+public interface Treatment {
+
+    // TODO: implement these later: modifications, group
+    // TODO: elsewhere provide factory methods for some default treatments
+
+    /**
+     * Returns the port number where the packet should be emitted.
+     *
+     * @return output port number
+     */
+    PortNumber output();
+
+}