diff --git a/src/main/java/net/onrc/onos/ofcontroller/flowprogrammer/IFlowPusherService.java b/src/main/java/net/onrc/onos/ofcontroller/flowprogrammer/IFlowPusherService.java
index e16dd20..94d6e35 100644
--- a/src/main/java/net/onrc/onos/ofcontroller/flowprogrammer/IFlowPusherService.java
+++ b/src/main/java/net/onrc/onos/ofcontroller/flowprogrammer/IFlowPusherService.java
@@ -1,43 +1,75 @@
 package net.onrc.onos.ofcontroller.flowprogrammer;
 
+import org.openflow.protocol.OFBarrierReply;
+import org.openflow.protocol.OFMessage;
+
 import net.floodlightcontroller.core.IOFSwitch;
+import net.floodlightcontroller.core.internal.OFMessageFuture;
 import net.floodlightcontroller.core.module.IFloodlightService;
 import net.onrc.onos.ofcontroller.core.INetMapTopologyObjects.IFlowEntry;
 import net.onrc.onos.ofcontroller.core.INetMapTopologyObjects.IFlowPath;
 import net.onrc.onos.ofcontroller.util.FlowEntry;
 import net.onrc.onos.ofcontroller.util.FlowPath;
 
-import org.openflow.protocol.OFMessage;
-
 public interface IFlowPusherService extends IFloodlightService {
 	/**
-	 * Add a message to the queue of a switch.
-	 * @param sw
-	 * @param msg
-	 * @return
+	 * Add a message to the queue of the switch.
+	 * @param sw Switch to which message is pushed.
+	 * @param msg Message object to be added.
+	 * @return true if message is successfully added to a queue.
 	 */
 	boolean add(IOFSwitch sw, OFMessage msg);
+
+	/**
+	 * Create a message from FlowEntry and add it to the queue of the switch.
+	 * @param sw Switch to which message is pushed.
+	 * @param flowPath FlowPath object used for creating message.
+	 * @param flowEntry FlowEntry object used for creating message.
+	 * @return true if message is successfully added to a queue.
+	 */
 	boolean add(IOFSwitch sw, FlowPath flowPath, FlowEntry flowEntry);
+
+	/**
+	 * Create a message from IFlowEntry and add it to the queue of the switch.
+	 * @param sw Switch to which message is pushed.
+	 * @param flowObj IFlowPath object used for creating message.
+	 * @param flowEntryObj IFlowEntry object used for creating message.
+	 * @return true if message is successfully added to a queue.
+	 */
 	boolean add(IOFSwitch sw, IFlowPath flowObj, IFlowEntry flowEntryObj);
+
+	/**
+	 * Add BARRIER message to queue and wait for reply.
+	 * @param sw Switch to which barrier message is pushed.
+	 * @return BARRIER_REPLY message sent from switch.
+	 */
+	OFBarrierReply barrier(IOFSwitch sw);
+	
+	/**
+	 * Add BARRIER message to queue asynchronously.
+	 * @param sw Switch to which barrier message is pushed.
+	 * @return Future object of BARRIER_REPLY message which will be sent from switch.
+	 */
+	OFMessageFuture<OFBarrierReply> barrierAsync(IOFSwitch sw);
 	
 	/**
 	 * Suspend pushing message to a switch.
-	 * @param sw
+	 * @param sw Switch to be suspended pushing message.
 	 * @return true if success
 	 */
 	boolean suspend(IOFSwitch sw);
 	
 	/**
 	 * Resume pushing message to a switch.
-	 * @param sw
+	 * @param sw Switch to be resumed pushing message.
 	 * @return true if success
 	 */
 	boolean resume(IOFSwitch sw);
 	
 	/**
 	 * Get whether pushing of message is suspended or not.
-	 * @param sw
-	 * @return true if suspended
+	 * @param sw Switch to be checked.
+	 * @return true if suspended.
 	 */
 	boolean isSuspended(IOFSwitch sw);
 }