diff --git a/src/main/java/net/onrc/onos/ofcontroller/networkgraph/NetworkGraph.java b/src/main/java/net/onrc/onos/ofcontroller/networkgraph/NetworkGraph.java
index 904e9a5..11f4405 100644
--- a/src/main/java/net/onrc/onos/ofcontroller/networkgraph/NetworkGraph.java
+++ b/src/main/java/net/onrc/onos/ofcontroller/networkgraph/NetworkGraph.java
@@ -84,13 +84,13 @@
     /**
      * Acquire a read lock on the entire topology. The topology will not 
      * change while readers have the lock. Must be released using 
-     * {@link releaseLock()}. This method will block until a read lock is
+     * {@link releaseReadLock()}. This method will block until a read lock is
      * available.
      */
-    public void acquireLock();
+    public void acquireReadLock();
 	
     /**
      * Release the read lock on the topology.
      */
-    public void releaseLock();
+    public void releaseReadLock();
 }
diff --git a/src/main/java/net/onrc/onos/ofcontroller/networkgraph/NetworkGraphImpl.java b/src/main/java/net/onrc/onos/ofcontroller/networkgraph/NetworkGraphImpl.java
index 83fc952..2153905 100644
--- a/src/main/java/net/onrc/onos/ofcontroller/networkgraph/NetworkGraphImpl.java
+++ b/src/main/java/net/onrc/onos/ofcontroller/networkgraph/NetworkGraphImpl.java
@@ -142,12 +142,20 @@
 	}
 
 	@Override
-	public void acquireLock() {
+	public void acquireReadLock() {
 		readLock.lock();
 	}
 
 	@Override
-	public void releaseLock() {
+	public void releaseReadLock() {
 		readLock.unlock();
 	}
+
+	protected void acquireWriteLock() {
+		writeLock.lock();
+	}
+
+	protected void releaseWriteLock() {
+		writeLock.unlock();
+	}
 }
diff --git a/src/main/java/net/onrc/onos/ofcontroller/networkgraph/TopologyManager.java b/src/main/java/net/onrc/onos/ofcontroller/networkgraph/TopologyManager.java
index e484d88..b07b4ff 100644
--- a/src/main/java/net/onrc/onos/ofcontroller/networkgraph/TopologyManager.java
+++ b/src/main/java/net/onrc/onos/ofcontroller/networkgraph/TopologyManager.java
@@ -269,6 +269,11 @@
 	    }
 
 	    //
+	    // Lock the Network Graph while it is modified
+	    //
+	    networkGraph.acquireWriteLock();
+
+	    //
 	    // Apply the classified events.
 	    //
 	    // Apply the "add" events in the proper order:
@@ -302,6 +307,11 @@
 				 ! addedPortEvents.isEmpty());
 
 	    //
+	    // Network Graph modifications completed: Release the lock
+	    //
+	    networkGraph.releaseWriteLock();
+
+	    //
 	    // Dispatch the Topology Notification Events to the applications
 	    //
 	    dispatchNetworkGraphEvents();