diff --git a/src/main/java/net/onrc/onos/core/flowprogrammer/FlowPusher.java b/src/main/java/net/onrc/onos/core/flowprogrammer/FlowPusher.java
index b27e0fd..a660cd6 100644
--- a/src/main/java/net/onrc/onos/core/flowprogrammer/FlowPusher.java
+++ b/src/main/java/net/onrc/onos/core/flowprogrammer/FlowPusher.java
@@ -6,12 +6,12 @@
 import java.util.Collection;
 import java.util.EnumSet;
 import java.util.HashMap;
-import java.util.HashSet;
+import java.util.Iterator;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
+import java.util.Map.Entry;
 import java.util.Queue;
-import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.locks.Condition;
@@ -324,14 +324,12 @@
                     }
                 }
 
-                // for safety of concurrent access, copy set of key objects
-                Set<IOFSwitch> keys = new HashSet<IOFSwitch>(assignedQueues.size());
-                for (IOFSwitch sw : assignedQueues.keySet()) {
-                    keys.add(sw);
-                }
-
-                for (IOFSwitch sw : keys) {
-                    SwitchQueue queue = assignedQueues.get(sw);
+                for (Iterator<Entry<IOFSwitch, SwitchQueue>> it = assignedQueues.entrySet().iterator();
+                        it.hasNext();
+                        ) {
+                    Entry<IOFSwitch, SwitchQueue> entry = it.next();
+                    IOFSwitch sw = entry.getKey();
+                    SwitchQueue queue = entry.getValue();
 
                     if (queue == null) {
                         continue;
@@ -341,7 +339,7 @@
                         processQueue(sw, queue, MAX_MESSAGE_SEND);
                         if (queue.toBeDeleted && !queue.hasMessageToSend()) {
                             // remove queue if flagged to be.
-                            assignedQueues.remove(sw);
+                            it.remove();
                         }
                     }
                 }
@@ -362,7 +360,7 @@
             long currentTime = System.currentTimeMillis();
             long size = 0;
 
-            if (queue.isSendable(currentTime)) {
+            if (sw.isConnected() && queue.isSendable(currentTime)) {
                 int i = 0;
                 while (queue.hasMessageToSend()) {
                     // Number of messages excess the limit
diff --git a/src/test/java/net/onrc/onos/core/flowprogrammer/FlowPusherTest.java b/src/test/java/net/onrc/onos/core/flowprogrammer/FlowPusherTest.java
index cf86358..89f188d 100644
--- a/src/test/java/net/onrc/onos/core/flowprogrammer/FlowPusherTest.java
+++ b/src/test/java/net/onrc/onos/core/flowprogrammer/FlowPusherTest.java
@@ -1,5 +1,18 @@
 package net.onrc.onos.core.flowprogrammer;
 
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+
 import net.floodlightcontroller.core.FloodlightContext;
 import net.floodlightcontroller.core.IFloodlightProviderService;
 import net.floodlightcontroller.core.IOFSwitch;
@@ -16,6 +29,7 @@
 import net.onrc.onos.core.util.FlowId;
 import net.onrc.onos.core.util.IntegrationTest;
 import net.onrc.onos.core.util.PortNumber;
+
 import org.easymock.EasyMock;
 import org.easymock.IAnswer;
 import org.junit.Test;
@@ -28,19 +42,6 @@
 import org.openflow.protocol.action.OFAction;
 import org.openflow.protocol.factory.BasicFactory;
 
-import java.io.IOException;
-import java.util.ArrayList;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-import java.util.concurrent.ScheduledExecutorService;
-import java.util.concurrent.TimeUnit;
-
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertNotNull;
-import static org.junit.Assert.assertTrue;
-import static org.junit.Assert.fail;
-
 @Category(IntegrationTest.class)
 public class FlowPusherTest {
     private FlowPusher pusher;
@@ -63,10 +64,7 @@
         EasyMock.expect(msg.getLength()).andReturn((short) 100).anyTimes();
         EasyMock.replay(msg);
 
-        IOFSwitch sw = EasyMock.createMock(IOFSwitch.class);
-        EasyMock.expect(sw.getId()).andReturn((long) 1).anyTimes();
-        sw.flush();
-        EasyMock.expectLastCall().once();
+        IOFSwitch sw = createConnectedSwitchMock(1, false);
         EasyMock.replay(sw);
 
         try {
@@ -105,10 +103,7 @@
 
         beginInitMock();
 
-        IOFSwitch sw = EasyMock.createMock(IOFSwitch.class);
-        EasyMock.expect(sw.getId()).andReturn((long) 1).anyTimes();
-        sw.flush();
-        EasyMock.expectLastCall().atLeastOnce();
+        IOFSwitch sw = createConnectedSwitchMock(1, false);
         EasyMock.replay(sw);
 
         List<OFMessage> messages = new ArrayList<OFMessage>();
@@ -164,10 +159,7 @@
 
         Map<IOFSwitch, List<OFMessage>> swMap = new HashMap<IOFSwitch, List<OFMessage>>();
         for (int i = 0; i < numSwitch; ++i) {
-            IOFSwitch sw = EasyMock.createMock(IOFSwitch.class);
-            EasyMock.expect(sw.getId()).andReturn((long) i).anyTimes();
-            sw.flush();
-            EasyMock.expectLastCall().atLeastOnce();
+            IOFSwitch sw = createConnectedSwitchMock(i, false);
             EasyMock.replay(sw);
 
             List<OFMessage> messages = new ArrayList<OFMessage>();
@@ -230,10 +222,7 @@
 
         Map<IOFSwitch, List<OFMessage>> swMap = new HashMap<IOFSwitch, List<OFMessage>>();
         for (int i = 0; i < numThreads; ++i) {
-            IOFSwitch sw = EasyMock.createMock(IOFSwitch.class);
-            EasyMock.expect(sw.getId()).andReturn((long) i).anyTimes();
-            sw.flush();
-            EasyMock.expectLastCall().atLeastOnce();
+            IOFSwitch sw = createConnectedSwitchMock(i, false);
             EasyMock.replay(sw);
 
             List<OFMessage> messages = new ArrayList<OFMessage>();
@@ -302,11 +291,7 @@
 
         beginInitMock();
 
-        IOFSwitch sw = EasyMock.createMock(IOFSwitch.class);
-        EasyMock.expect(sw.getId()).andReturn((long) 1).anyTimes();
-        sw.flush();
-        EasyMock.expectLastCall().atLeastOnce();
-        prepareBarrier(sw);
+        IOFSwitch sw = createConnectedSwitchMock(1, true);
         EasyMock.replay(sw);
 
         List<OFMessage> messages = new ArrayList<OFMessage>();
@@ -384,11 +369,7 @@
     public void testBarrierMessage() {
         beginInitMock();
 
-        IOFSwitch sw = EasyMock.createMock(IOFSwitch.class);
-        EasyMock.expect(sw.getId()).andReturn((long) 1).anyTimes();
-        sw.flush();
-        EasyMock.expectLastCall().atLeastOnce();
-        prepareBarrier(sw);
+        IOFSwitch sw = createConnectedSwitchMock(1, true);
         EasyMock.replay(sw);
 
         try {
@@ -457,11 +438,8 @@
 
         EasyMock.expect(factory.getMessage(EasyMock.eq(OFType.FLOW_MOD))).andReturn(msg);
 
-        IOFSwitch sw = EasyMock.createMock(IOFSwitch.class);
-        EasyMock.expect(sw.getId()).andReturn(DPID_TO_VERIFY).anyTimes();
+        IOFSwitch sw = createConnectedSwitchMock(DPID_TO_VERIFY, false);
         EasyMock.expect(sw.getStringId()).andReturn("1").anyTimes();
-        sw.flush();
-        EasyMock.expectLastCall().once();
 
         try {
             EasyMock.expect(damper.write(EasyMock.eq(sw), EasyMock.anyObject(OFMessage.class), EasyMock.eq(context)))
@@ -545,6 +523,19 @@
         pusher.start();
     }
 
+    private IOFSwitch createConnectedSwitchMock(long dpid, boolean useBarrier) {
+        IOFSwitch sw = EasyMock.createMock(IOFSwitch.class);
+        EasyMock.expect(sw.isConnected()).andReturn(true).anyTimes();
+        EasyMock.expect(sw.getId()).andReturn(dpid).anyTimes();
+        sw.flush();
+        EasyMock.expectLastCall().atLeastOnce();
+        if (useBarrier) {
+            prepareBarrier(sw);
+        }
+
+        return sw;
+    }
+
     private void prepareBarrier(IOFSwitch sw) {
         OFBarrierRequest req = EasyMock.createMock(OFBarrierRequest.class);
         req.setXid(EasyMock.anyInt());