diff --git a/src/main/java/net/onrc/onos/ofcontroller/flowprogrammer/FlowPusher.java b/src/main/java/net/onrc/onos/ofcontroller/flowprogrammer/FlowPusher.java
index ba3602c..6f85c5d 100644
--- a/src/main/java/net/onrc/onos/ofcontroller/flowprogrammer/FlowPusher.java
+++ b/src/main/java/net/onrc/onos/ofcontroller/flowprogrammer/FlowPusher.java
@@ -40,17 +40,20 @@
 import net.onrc.onos.ofcontroller.util.Port;
 
 /**
- * FlowPusher intermediates FlowManager/FlowSynchronizer and switches to push OpenFlow
- * messages to switches in proper rate.
+ * FlowPusher is a implementation of FlowPusherService.
+ * FlowPusher assigns one message queue instance for each one switch.
+ * Number of message processing threads is configurable by constructor, and
+ * one thread can handle multiple message queues. Each queue will be assigned to 
+ * a thread according to hash function defined by getHash().
+ * Each processing thread reads messages from queues and sends it to switches
+ * in round-robin. Processing thread also calculates rate of sending to suppress
+ * excessive message sending.
  * @author Naoki Shiota
  *
  */
 public class FlowPusher implements IFlowPusherService, IOFMessageListener {
     private final static Logger log = LoggerFactory.getLogger(FlowPusher.class);
 
-    // If this flag is true, barrier message will be sent when queue goes empty.
-    private static boolean barrierIfEmpty = false;
-    
     // NOTE: Below are moved from FlowManager.
     // TODO: Values copied from elsewhere (class LearningSwitch).
     // The local copy should go away!
@@ -71,7 +74,7 @@
 	}
 	
 	/**
-	 * Message queue attached to a switch.
+	 * SwitchQueue represents message queue attached to a switch.
 	 * This consists of queue itself and variables used for limiting sending rate.
 	 * @author Naoki Shiota
 	 *
@@ -104,8 +107,7 @@
 			}
 			
 			// Check if sufficient time (from aspect of rate) elapsed or not.
-			long interval = (current - last_sent_time) / 1000000;
-			long rate = last_sent_size / interval;
+			long rate = last_sent_size / (current - last_sent_time);
 			return (rate < max_rate);
 		}
 		
@@ -126,7 +128,10 @@
 
 	private FloodlightContext context = null;
 	private BasicFactory factory = null;
+	
+	// Map of threads versus dpid
 	private Map<Long, FlowPusherThread> threadMap = null;
+	// Map of Future objects versus dpid and transaction ID.
 	private Map<Long, Map<Integer, OFBarrierReplyFuture>>
 		barrierFutures = new HashMap<Long, Map<Integer, OFBarrierReplyFuture>>();
 	
@@ -139,14 +144,12 @@
 	 */
 	private class FlowPusherThread extends Thread {
 		private Map<IOFSwitch,SwitchQueue> queues
-		= new HashMap<IOFSwitch,SwitchQueue>();
+			= new HashMap<IOFSwitch,SwitchQueue>();
 		
 		private Semaphore mutex = new Semaphore(0);
 		
 		@Override
 		public void run() {
-			log.debug("Begin Flow Pusher Process");
-			
 			while (true) {
 				try {
 					// wait for message pushed to queue
@@ -173,7 +176,7 @@
 					}
 					
 					// check sending rate and determine it to be sent or not
-					long current_time = System.nanoTime();
+					long current_time = System.currentTimeMillis();
 					long size = 0;
 					
 					synchronized (queue) {
@@ -202,9 +205,7 @@
 							queue.logSentData(current_time, size);
 							
 							if (queue.isEmpty()) {
-								if (barrierIfEmpty) {
-									barrier(sw);
-								}
+								// remove queue if flagged to be.
 								if (queue.toBeDeleted) {
 									synchronized (queues) {
 										queues.remove(sw);
@@ -255,7 +256,7 @@
 		if (damper != null) {
 			messageDamper = damper;
 		} else {
-			// use default value
+			// use default values
 			messageDamper = new OFMessageDamper(OFMESSAGE_DAMPER_CAPACITY,
 				    EnumSet.of(OFType.FLOW_MOD),
 				    OFMESSAGE_DAMPER_TIMEOUT);
@@ -280,10 +281,6 @@
 		}
 	}
 	
-	/**
-	 * Suspend sending messages to switch.
-	 * @param sw
-	 */
 	@Override
 	public boolean suspend(IOFSwitch sw) {
 		SwitchQueue queue = getQueue(sw);
@@ -301,9 +298,6 @@
 		}
 	}
 
-	/**
-	 * Resume sending messages to switch.
-	 */
 	@Override
 	public boolean resume(IOFSwitch sw) {
 		SwitchQueue queue = getQueue(sw);
@@ -321,9 +315,6 @@
 		}
 	}
 	
-	/**
-	 * Check if given switch is suspended.
-	 */
 	@Override
 	public boolean isSuspended(IOFSwitch sw) {
 		SwitchQueue queue = getQueue(sw);
@@ -384,10 +375,10 @@
 	}
 	
 	@Override
-	public boolean deleteQueue(IOFSwitch sw, boolean force) {
+	public boolean deleteQueue(IOFSwitch sw, boolean forceStop) {
 		FlowPusherThread proc = getProcess(sw);
 		
-		if (force) {
+		if (forceStop) {
 			synchronized (proc.queues) {
 				SwitchQueue queue = proc.queues.remove(sw);
 				if (queue == null) {
@@ -407,18 +398,12 @@
 		}
 	}
 	
-	/**
-	 * Add OFMessage to queue of the switch.
-	 * @param sw Switch to which message is sent.
-	 * @param msg Message to be sent.
-	 * @return true if succeed.
-	 */
 	@Override
 	public boolean add(IOFSwitch sw, OFMessage msg) {
 		FlowPusherThread proc = getProcess(sw);
 		SwitchQueue queue = proc.queues.get(sw);
 
-		// create queue at first call
+		// create queue at first addition of message
 		if (queue == null) {
 			createQueue(sw);
 			queue = getQueue(sw);
@@ -436,13 +421,6 @@
 		return true;
 	}
 	
-	/**
-	 * Create OFMessage from given flow information and add it to the queue.
-	 * @param sw Switch to which message is sent.
-	 * @param flowObj FlowPath.
-	 * @param flowEntryObj FlowEntry.
-	 * @return true if succeed.
-	 */
 	@Override
 	public boolean add(IOFSwitch sw, IFlowPath flowObj, IFlowEntry flowEntryObj) {
 		log.debug("sending : {}, {}", sw, flowObj);
@@ -748,13 +726,6 @@
 		return true;
 	}
 	
-	/**
-	 * Create OFMessage from given flow information and add it to the queue.
-	 * @param sw Switch to which message is sent.
-	 * @param flowPath FlowPath.
-	 * @param flowEntry FlowEntry.
-	 * @return true if succeed.
-	 */
 	@Override
 	public boolean add(IOFSwitch sw, FlowPath flowPath, FlowEntry flowEntry) {
 		//