diff --git a/src/main/java/net/floodlightcontroller/core/internal/OFSwitchImpl.java b/src/main/java/net/floodlightcontroller/core/internal/OFSwitchImpl.java
index ce865d8..0bb9f2f 100644
--- a/src/main/java/net/floodlightcontroller/core/internal/OFSwitchImpl.java
+++ b/src/main/java/net/floodlightcontroller/core/internal/OFSwitchImpl.java
@@ -23,10 +23,10 @@
 import java.util.Collection;
 import java.util.Collections;
 import java.util.Date;
-import java.util.HashMap;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
+import java.util.WeakHashMap;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
 import java.util.concurrent.Future;
@@ -135,7 +135,7 @@
             new ThreadLocal<Map<OFSwitchImpl, List<OFMessage>>>() {
                 @Override
                 protected Map<OFSwitchImpl, List<OFMessage>> initialValue() {
-                    return new HashMap<OFSwitchImpl, List<OFMessage>>();
+                    return new WeakHashMap<OFSwitchImpl, List<OFMessage>>();
                 }
             };
 
diff --git a/src/main/java/net/floodlightcontroller/util/OFMessageDamper.java b/src/main/java/net/floodlightcontroller/util/OFMessageDamper.java
index 47a92a9..5faf38e 100644
--- a/src/main/java/net/floodlightcontroller/util/OFMessageDamper.java
+++ b/src/main/java/net/floodlightcontroller/util/OFMessageDamper.java
@@ -6,7 +6,10 @@
 
 import java.io.IOException;
 import java.util.EnumSet;
+import java.util.Iterator;
 import java.util.Set;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
 
 import net.floodlightcontroller.core.FloodlightContext;
 import net.floodlightcontroller.core.IOFSwitch;
@@ -81,6 +84,8 @@
 
     TimedCache<DamperEntry> cache;
     EnumSet<OFType> msgTypesToCache;
+    // executor for invalidate task
+    private static ExecutorService executor = Executors.newFixedThreadPool(1);
 
     /**
      * @param capacity      the maximum number of messages that should be
@@ -147,4 +152,24 @@
             return true;
         }
     }
+
+    /**
+     * Invalidates all the damper cache entries for the specified switch.
+     *
+     * @param sw switch connection to invalidate
+     */
+    public void invalidate(final IOFSwitch sw) {
+        executor.submit(new Runnable() {
+            @Override
+            public void run() {
+                Iterator<DamperEntry> it = cache.getCachedEntries().iterator();
+                while (it.hasNext()) {
+                    DamperEntry entry = it.next();
+                    if (entry.sw == sw) {
+                        it.remove();
+                    }
+                }
+            }
+        });
+   }
 }
diff --git a/src/main/java/net/floodlightcontroller/util/TimedCache.java b/src/main/java/net/floodlightcontroller/util/TimedCache.java
index 2a90f0b..76f1e57 100644
--- a/src/main/java/net/floodlightcontroller/util/TimedCache.java
+++ b/src/main/java/net/floodlightcontroller/util/TimedCache.java
@@ -17,6 +17,7 @@
 
 package net.floodlightcontroller.util;
 
+import java.util.Set;
 import java.util.concurrent.ConcurrentMap;
 
 import com.googlecode.concurrentlinkedhashmap.ConcurrentLinkedHashMap;
@@ -60,7 +61,7 @@
      * @return boolean
      */
     public boolean update(K key) {
-        Long curr = new Long(System.currentTimeMillis());
+        long curr = System.currentTimeMillis();
         Long prev = cache.putIfAbsent(key, curr);
 
         if (prev == null) {
@@ -75,4 +76,15 @@
 
         return true;
     }
+
+    /**
+     * Gets all the cached entries.
+     * <p/>
+     * Modification to the returned set will be reflected to the cache.
+     *
+     * @return cached entries
+     */
+    Set<K> getCachedEntries() {
+        return cache.keySet();
+    }
 }
diff --git a/src/main/java/net/onrc/onos/core/flowprogrammer/FlowProgrammer.java b/src/main/java/net/onrc/onos/core/flowprogrammer/FlowProgrammer.java
index 838533d..046d130 100644
--- a/src/main/java/net/onrc/onos/core/flowprogrammer/FlowProgrammer.java
+++ b/src/main/java/net/onrc/onos/core/flowprogrammer/FlowProgrammer.java
@@ -128,6 +128,7 @@
             synchronizer.interrupt(sw);
         }
         pusher.deleteQueue(sw, true);
+        pusher.invalidate(sw);
     }
 
     @Override
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 98c2f97..37e1b44 100644
--- a/src/main/java/net/onrc/onos/core/flowprogrammer/FlowPusher.java
+++ b/src/main/java/net/onrc/onos/core/flowprogrammer/FlowPusher.java
@@ -70,6 +70,8 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import com.google.common.cache.CacheBuilder;
+
 import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
 
 /**
@@ -299,8 +301,11 @@
      * Main thread that reads messages from queues and sends them to switches.
      */
     private class FlowPusherThread extends Thread {
+        // Weak ConncurrentHashMap
         private Map<IOFSwitch, SwitchQueue> assignedQueues
-                = new ConcurrentHashMap<IOFSwitch, SwitchQueue>();
+                = CacheBuilder.newBuilder()
+                    .weakKeys()
+                    .<IOFSwitch, SwitchQueue>build().asMap();
 
         final Lock queuingLock = new ReentrantLock();
         final Condition messagePushed = queuingLock.newCondition();
@@ -612,6 +617,17 @@
         }
     }
 
+    /**
+     * Invalidate.
+     *
+     * @param sw switch
+     *
+     * @see OFMessageDamper#invalidate(IOFSwitch)
+     */
+    public void invalidate(IOFSwitch sw) {
+        messageDamper.invalidate(sw);
+    }
+
     @Override
     public boolean add(IOFSwitch sw, OFMessage msg) {
         return add(sw, msg, MsgPriority.NORMAL);
diff --git a/src/main/java/net/onrc/onos/core/intent/runtime/PlanInstallRuntime.java b/src/main/java/net/onrc/onos/core/intent/runtime/PlanInstallRuntime.java
index bd332ac..f942fa8 100644
--- a/src/main/java/net/onrc/onos/core/intent/runtime/PlanInstallRuntime.java
+++ b/src/main/java/net/onrc/onos/core/intent/runtime/PlanInstallRuntime.java
@@ -1,11 +1,12 @@
 package net.onrc.onos.core.intent.runtime;
 
+import java.lang.ref.WeakReference;
 import java.util.ArrayList;
-import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.WeakHashMap;
 import java.util.concurrent.ExecutionException;
 
 import net.floodlightcontroller.core.IFloodlightProviderService;
@@ -50,7 +51,7 @@
      * TODO: This class should be wrapped into a more generic debugging framework when available.
      */
     private static class FlowModCount {
-        IOFSwitch sw;
+        WeakReference<IOFSwitch> sw;
         long modFlows = 0;
         long delFlows = 0;
         long errors = 0;
@@ -61,7 +62,7 @@
          * @param sw the switch for FlowMod statistics collection
          */
         FlowModCount(IOFSwitch sw) {
-            this.sw = sw;
+            this.sw = new WeakReference<>(sw);
         }
 
         /**
@@ -92,10 +93,12 @@
          */
         @Override
         public String toString() {
-            return "sw:" + sw.getStringId() + ": modify " + modFlows + " delete " + delFlows + " error " + errors;
+            final IOFSwitch swTemp = sw.get();
+            return "sw:" + ((swTemp == null) ? "disconnected" : swTemp.getStringId())
+                    + ": modify " + modFlows + " delete " + delFlows + " error " + errors;
         }
 
-        static Map<IOFSwitch, FlowModCount> map = new HashMap<>();
+        static Map<IOFSwitch, FlowModCount> map = new WeakHashMap<>();
 
         /**
          * This function is used for collecting statistics information. It should be called for