diff --git a/src/main/java/net/onrc/onos/ofcontroller/floodlightlistener/RCNetworkGraphPublisher.java b/src/main/java/net/onrc/onos/ofcontroller/floodlightlistener/RCNetworkGraphPublisher.java
index 9d58be5..f8bbf22 100644
--- a/src/main/java/net/onrc/onos/ofcontroller/floodlightlistener/RCNetworkGraphPublisher.java
+++ b/src/main/java/net/onrc/onos/ofcontroller/floodlightlistener/RCNetworkGraphPublisher.java
@@ -218,9 +218,7 @@
 		for (OFPhysicalPort port : sw.getPorts()) {
 			portEvents.add(new PortEvent(sw.getId(), (long)port.getPortNumber()));
 		}
-		switchEvent.setPorts(portEvents);
-		
-		networkGraphDiscoveryInterface.putSwitchDiscoveryEvent(switchEvent);
+		networkGraphDiscoveryInterface.putSwitchDiscoveryEvent(switchEvent, portEvents);
 
 		/*
 		// TODO publish ADD_SWITCH event here
diff --git a/src/main/java/net/onrc/onos/ofcontroller/networkgraph/NetworkGraphDatastore.java b/src/main/java/net/onrc/onos/ofcontroller/networkgraph/NetworkGraphDatastore.java
index 61dde3a..dca4eb0 100644
--- a/src/main/java/net/onrc/onos/ofcontroller/networkgraph/NetworkGraphDatastore.java
+++ b/src/main/java/net/onrc/onos/ofcontroller/networkgraph/NetworkGraphDatastore.java
@@ -2,6 +2,7 @@
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Collection;
 
 import net.onrc.onos.datastore.RCObject;
 import net.onrc.onos.datastore.RCObject.WriteOp;
@@ -36,9 +37,11 @@
 	 * Add a switch to the database.
 	 *
 	 * @param sw the switch to add.
+	 * @param portEvents the corresponding switch ports to add.
 	 * @return true on success, otherwise false.
 	 */
-	public boolean addSwitch(SwitchEvent sw) {
+	public boolean addSwitch(SwitchEvent sw,
+				 Collection<PortEvent> portEvents) {
 		log.debug("Adding switch {}", sw);
 		ArrayList<WriteOp> groupOp = new ArrayList<>();
 
@@ -50,7 +53,7 @@
 		// to assure that DPID is unique cluster-wide, etc.
 		groupOp.add(WriteOp.ForceCreate(rcSwitch));
 
-		for (PortEvent portEvent : sw.getPorts()) {
+		for (PortEvent portEvent : portEvents) {
 			RCPort rcPort = new RCPort(sw.getDpid(), portEvent.getNumber());
 			rcPort.setStatus(RCPort.STATUS.ACTIVE);
 
@@ -75,9 +78,11 @@
 	 * Update a switch as inactive in the database.
 	 *
 	 * @param sw the switch to update.
+	 * @param portEvents the corresponding switch ports to update.
 	 * @return true on success, otherwise false.
 	 */
-	public boolean deactivateSwitch(SwitchEvent sw) {
+	public boolean deactivateSwitch(SwitchEvent sw,
+					Collection<PortEvent> portEvents) {
 		log.debug("Deactivating switch {}", sw);
 		RCSwitch rcSwitch = new RCSwitch(sw.getDpid());
 
@@ -86,7 +91,7 @@
 
 		groupOp.add(WriteOp.ForceCreate(rcSwitch));
 
-		for (PortEvent portEvent : sw.getPorts()) {
+		for (PortEvent portEvent : portEvents) {
 			RCPort rcPort = new RCPort(sw.getDpid(), (long)portEvent.getNumber());
 			rcPort.setStatus(RCPort.STATUS.INACTIVE);
 
@@ -94,7 +99,7 @@
 		}
 
 		boolean failed = RCObject.multiWrite(groupOp);
-		
+
 		return !failed;
 	}
 
diff --git a/src/main/java/net/onrc/onos/ofcontroller/networkgraph/NetworkGraphDiscoveryInterface.java b/src/main/java/net/onrc/onos/ofcontroller/networkgraph/NetworkGraphDiscoveryInterface.java
index 87edb28..cabcd38 100644
--- a/src/main/java/net/onrc/onos/ofcontroller/networkgraph/NetworkGraphDiscoveryInterface.java
+++ b/src/main/java/net/onrc/onos/ofcontroller/networkgraph/NetworkGraphDiscoveryInterface.java
@@ -1,5 +1,7 @@
 package net.onrc.onos.ofcontroller.networkgraph;
 
+import java.util.Collection;
+
 /**
  * Interface used by the Topology Discovery module to write topology-related
  * events.
@@ -9,8 +11,10 @@
      * Switch discovered event.
      *
      * @param switchEvent the switch event.
+     * @param portEvents the corresponding port events for the switch.
      */
-    public void putSwitchDiscoveryEvent(SwitchEvent switchEvent);
+    public void putSwitchDiscoveryEvent(SwitchEvent switchEvent,
+					Collection<PortEvent> portEvents);
 
     /**
      * Switch removed event.
diff --git a/src/main/java/net/onrc/onos/ofcontroller/networkgraph/SwitchEvent.java b/src/main/java/net/onrc/onos/ofcontroller/networkgraph/SwitchEvent.java
index dce0725..ea5b66d 100644
--- a/src/main/java/net/onrc/onos/ofcontroller/networkgraph/SwitchEvent.java
+++ b/src/main/java/net/onrc/onos/ofcontroller/networkgraph/SwitchEvent.java
@@ -5,7 +5,7 @@
 import java.util.List;
 
 /**
- * Self-contained Switch and Port event Object
+ * Self-contained Switch Object
  *
  * TODO: We probably want common base class/interface for Self-Contained Event Object
  *
@@ -13,8 +13,6 @@
 public class SwitchEvent {
     private final Long dpid;
 
-    private List<PortEvent> ports;
-
     /**
      * Default constructor.
      */
@@ -23,26 +21,13 @@
     }
 
     public SwitchEvent(Long dpid) {
-	this(dpid, new ArrayList<PortEvent>());
-    }
-
-    public SwitchEvent(Long dpid, List<PortEvent> ports) {
 	this.dpid = dpid;
-	this.ports = ports;
     }
 
     public Long getDpid() {
 	return dpid;
     }
 
-    public List<PortEvent> getPorts() {
-	return ports;
-    }
-
-    public void setPorts(List<PortEvent> ports) {
-	this.ports = ports;
-    }
-
     @Override
     public String toString() {
 	return "[SwitchEvent 0x" + Long.toHexString(dpid) + "]";
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 f620614..ebe9900 100644
--- a/src/main/java/net/onrc/onos/ofcontroller/networkgraph/TopologyManager.java
+++ b/src/main/java/net/onrc/onos/ofcontroller/networkgraph/TopologyManager.java
@@ -1,11 +1,14 @@
 package net.onrc.onos.ofcontroller.networkgraph;
 
 import java.net.InetAddress;
+import java.nio.ByteBuffer;
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.HashMap;
 import java.util.HashSet;
 import java.util.LinkedList;
 import java.util.List;
+import java.util.Map;
 import java.util.Set;
 import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.CopyOnWriteArrayList;
@@ -53,6 +56,24 @@
     private final IControllerRegistryService registryService;
     private CopyOnWriteArrayList<INetworkGraphListener> networkGraphListeners;
 
+    // Local state for computing the final set of events
+    private Map<ByteBuffer, SwitchEvent> addedSwitchEvents =
+	new HashMap<ByteBuffer, SwitchEvent>();
+    private Map<ByteBuffer, SwitchEvent> removedSwitchEvents =
+	new HashMap<ByteBuffer, SwitchEvent>();
+    private Map<ByteBuffer, PortEvent> addedPortEvents =
+	new HashMap<ByteBuffer, PortEvent>();
+    private Map<ByteBuffer, PortEvent> removedPortEvents =
+	new HashMap<ByteBuffer, PortEvent>();
+    private Map<ByteBuffer, LinkEvent> addedLinkEvents =
+	new HashMap<ByteBuffer, LinkEvent>();
+    private Map<ByteBuffer, LinkEvent> removedLinkEvents =
+	new HashMap<ByteBuffer, LinkEvent>();
+    private Map<ByteBuffer, DeviceEvent> addedDeviceEvents =
+	new HashMap<ByteBuffer, DeviceEvent>();
+    private Map<ByteBuffer, DeviceEvent> removedDeviceEvents =
+	new HashMap<ByteBuffer, DeviceEvent>();
+
     /**
      * Constructor.
      *
@@ -89,7 +110,11 @@
 	 */
 	private void startup() {
 	    //
-	    // TODO: Read all state from the database
+	    // TODO: Read all state from the database:
+	    //
+	    // Collection<EventEntry<TopologyEvent>> collection =
+	    //    readWholeTopologyFromDB();
+	    //
 	    // For now, as a shortcut we read it from the datagrid
 	    //
 	    Collection<TopologyEvent> topologyEvents =
@@ -142,28 +167,60 @@
 	private void processEvents(Collection<EventEntry<TopologyEvent>> events) {
 	    for (EventEntry<TopologyEvent> event : events) {
 		TopologyEvent topologyEvent = event.eventData();
+		SwitchEvent switchEvent = topologyEvent.switchEvent;
+		PortEvent portEvent = topologyEvent.portEvent;
+		LinkEvent linkEvent = topologyEvent.linkEvent;
+		DeviceEvent deviceEvent = topologyEvent.deviceEvent;
+
+		//
+		// Extract the events by cancelling matching events
+		//
 		switch (event.eventType()) {
 		case ENTRY_ADD:
 		    log.debug("Topology event ENTRY_ADD: {}", topologyEvent);
-		    if (topologyEvent.switchEvent != null)
-			putSwitchReplicationEvent(topologyEvent.switchEvent);
-		    if (topologyEvent.portEvent != null)
-			putPortReplicationEvent(topologyEvent.portEvent);
-		    if (topologyEvent.linkEvent != null)
-			putLinkReplicationEvent(topologyEvent.linkEvent);
-		    if (topologyEvent.deviceEvent != null)
-			putDeviceReplicationEvent(topologyEvent.deviceEvent);
+		    if (switchEvent != null) {
+			ByteBuffer id = ByteBuffer.wrap(switchEvent.getID());
+			addedSwitchEvents.put(id, switchEvent);
+			removedSwitchEvents.remove(id);
+		    }
+		    if (portEvent != null) {
+			ByteBuffer id = ByteBuffer.wrap(portEvent.getID());
+			addedPortEvents.put(id, portEvent);
+			removedPortEvents.remove(id);
+		    }
+		    if (linkEvent != null) {
+			ByteBuffer id = ByteBuffer.wrap(linkEvent.getID());
+			addedLinkEvents.put(id, linkEvent);
+			removedLinkEvents.remove(id);
+		    }
+		    if (deviceEvent != null) {
+			ByteBuffer id = ByteBuffer.wrap(deviceEvent.getID());
+			addedDeviceEvents.put(id, deviceEvent);
+			removedDeviceEvents.remove(id);
+		    }
 		    break;
 		case ENTRY_REMOVE:
 		    log.debug("Topology event ENTRY_REMOVE: {}", topologyEvent);
-		    if (topologyEvent.switchEvent != null)
-			removeSwitchReplicationEvent(topologyEvent.switchEvent);
-		    if (topologyEvent.portEvent != null)
-			removePortReplicationEvent(topologyEvent.portEvent);
-		    if (topologyEvent.linkEvent != null)
-			removeLinkReplicationEvent(topologyEvent.linkEvent);
-		    if (topologyEvent.deviceEvent != null)
-			removeDeviceReplicationEvent(topologyEvent.deviceEvent);
+		    if (switchEvent != null) {
+			ByteBuffer id = ByteBuffer.wrap(switchEvent.getID());
+			addedSwitchEvents.remove(id);
+			removedSwitchEvents.put(id, switchEvent);
+		    }
+		    if (portEvent != null) {
+			ByteBuffer id = ByteBuffer.wrap(portEvent.getID());
+			addedPortEvents.remove(id);
+			removedPortEvents.put(id, portEvent);
+		    }
+		    if (linkEvent != null) {
+			ByteBuffer id = ByteBuffer.wrap(linkEvent.getID());
+			addedLinkEvents.remove(id);
+			removedLinkEvents.put(id, linkEvent);
+		    }
+		    if (deviceEvent != null) {
+			ByteBuffer id = ByteBuffer.wrap(deviceEvent.getID());
+			addedDeviceEvents.remove(id);
+			removedDeviceEvents.put(id, deviceEvent);
+		    }
 		    break;
 		}
 	    }
@@ -243,19 +300,32 @@
      * ******************************/
 
     @Override
-    public void putSwitchDiscoveryEvent(SwitchEvent switchEvent) {
-	if (datastore.addSwitch(switchEvent)) {
+    public void putSwitchDiscoveryEvent(SwitchEvent switchEvent,
+					Collection<PortEvent> portEvents) {
+	if (datastore.addSwitch(switchEvent, portEvents)) {
 	    // Send out notification
 	    TopologyEvent topologyEvent = new TopologyEvent(switchEvent);
 	    eventChannel.addEntry(topologyEvent.getID(), topologyEvent);
+
+	    for (PortEvent portEvent : portEvents) {
+		topologyEvent = new TopologyEvent(portEvent);
+		eventChannel.addEntry(topologyEvent.getID(), topologyEvent);
+	    }
 	}
     }
 
     @Override
     public void removeSwitchDiscoveryEvent(SwitchEvent switchEvent) {
-	if (datastore.deactivateSwitch(switchEvent)) {
+	// TODO: Use a copy of the port events previously added for that switch
+	Collection<PortEvent> portEvents = new LinkedList<PortEvent>();
+
+	if (datastore.deactivateSwitch(switchEvent, portEvents)) {
 	    // Send out notification
 	    eventChannel.removeEntry(switchEvent.getID());
+
+	    for (PortEvent portEvent : portEvents) {
+		eventChannel.removeEntry(portEvent.getID());
+	    }
 	}
     }
 
@@ -264,6 +334,7 @@
 	if (datastore.addPort(portEvent)) {
 	    // Send out notification
 	    TopologyEvent topologyEvent = new TopologyEvent(portEvent);
+	    eventChannel.addEntry(topologyEvent.getID(), topologyEvent);
 	}
     }
 
@@ -309,82 +380,6 @@
 	}
     }
 
-    /* ************************************************
-     * Internal methods for processing the replication events
-     * ************************************************/
-
-    private void putSwitchReplicationEvent(SwitchEvent switchEvent) {
-	if (prepareForAddSwitchEvent(switchEvent)) {
-	    putSwitch(switchEvent);
-	}
-	// TODO handle invariant violation
-	// trigger instance local topology event handler
-	dispatchPutSwitchEvent(switchEvent);
-    }
-
-    private void removeSwitchReplicationEvent(SwitchEvent switchEvent) {
-	if (prepareForRemoveSwitchEvent(switchEvent)) {
-	    removeSwitch(switchEvent);
-	}
-	// TODO handle invariant violation
-	// trigger instance local topology event handler
-	dispatchRemoveSwitchEvent(switchEvent);
-    }
-
-    private void putPortReplicationEvent(PortEvent portEvent) {
-	if (prepareForAddPortEvent(portEvent)) {
-	    putPort(portEvent);
-	}
-	// TODO handle invariant violation
-	// trigger instance local topology event handler
-	dispatchPutPortEvent(portEvent);
-    }
-
-    private void removePortReplicationEvent(PortEvent portEvent) {
-	if (prepareForRemovePortEvent(portEvent)) {
-	    removePort(portEvent);
-	}
-	// TODO handle invariant violation
-	// trigger instance local topology event handler
-	dispatchRemovePortEvent(portEvent);
-    }
-
-    private void putLinkReplicationEvent(LinkEvent linkEvent) {
-	if (prepareForAddLinkEvent(linkEvent)) {
-	    putLink(linkEvent);
-	}
-	// TODO handle invariant violation
-	// trigger instance local topology event handler
-	dispatchPutLinkEvent(linkEvent);
-    }
-
-    private void removeLinkReplicationEvent(LinkEvent linkEvent) {
-	if (prepareForRemoveLinkEvent(linkEvent)) {
-	    removeLink(linkEvent);
-	}
-	// TODO handle invariant violation
-	// trigger instance local topology event handler
-	dispatchRemoveLinkEvent(linkEvent);
-    }
-
-    private void putDeviceReplicationEvent(DeviceEvent deviceEvent) {
-	if (prepareForAddDeviceEvent(deviceEvent)) {
-	    putDevice(deviceEvent);
-	}
-	// TODO handle invariant violation
-	// trigger instance local topology event handler
-	dispatchPutDeviceEvent(deviceEvent);
-    }
-
-    private void removeDeviceReplicationEvent(DeviceEvent deviceEvent) {
-	if (prepareForRemoveDeviceEvent(deviceEvent)) {
-	    removeDevice(deviceEvent);
-	}
-	// TODO handle invariant violation
-	// trigger instance local topology event handler
-	dispatchRemoveDeviceEvent(deviceEvent);
-    }
-
     /* *****************
      * Internal methods to maintain invariants of the network graph
      * *****************/
@@ -396,50 +391,14 @@
      */
     private boolean prepareForAddSwitchEvent(SwitchEvent swEvent) {
 	// No show stopping precondition
-	// Prep: remove(deactivate) Ports on Switch, which is not on event
-	removePortsNotOnEvent(swEvent);
 	return true;
     }
 
     private boolean prepareForRemoveSwitchEvent(SwitchEvent swEvent) {
 	// No show stopping precondition
-	// Prep: remove(deactivate) Ports on Switch, which is not on event
-	// XXX may be remove switch should imply wipe all ports
-	removePortsNotOnEvent(swEvent);
 	return true;
     }
 
-    private void removePortsNotOnEvent(SwitchEvent swEvent) {
-	Switch sw = networkGraph.getSwitch(swEvent.getDpid());
-	if (sw != null) {
-	    Set<Long> port_noOnEvent = new HashSet<>();
-	    for (PortEvent portEvent : swEvent.getPorts()) {
-		port_noOnEvent.add(portEvent.getNumber());
-	    }
-	    // Existing ports not on event should be removed.
-	    // TODO Should batch eventually for performance?
-	    List<Port> portsToRemove = new ArrayList<Port>();
-	    for (Port p : sw.getPorts()) {
-		if (!port_noOnEvent.contains(p.getNumber())) {
-		    //PortEvent rmEvent = new PortEvent(p.getSwitch().getDpid(), p.getNumber());
-		    // calling Discovery removePort() API to wipe from DB, etc.
-		    //removePortDiscoveryEvent(rmEvent);
-
-		    // We can't remove ports here because this will trigger a remove
-		    // from the switch's port list, which we are currently iterating
-		    // over.
-		    portsToRemove.add(p);
-		}
-	    }
-	    for (Port p : portsToRemove) {
-		PortEvent rmEvent = new PortEvent(p.getSwitch().getDpid(),
-						  p.getNumber());
-		// calling Discovery removePort() API to wipe from DB, etc.
-		removePortDiscoveryEvent(rmEvent);
-	    }
-	}
-    }
-
     private boolean prepareForAddPortEvent(PortEvent portEvent) {
 	// Parent Switch must exist
 	if (networkGraph.getSwitch(portEvent.getDpid()) == null) {
@@ -627,11 +586,6 @@
 
 	// Update when more attributes are added to Event object
 	// no attribute to update for now
-
-	// TODO handle child Port event properly for performance
-	for (PortEvent portEvent : swEvent.getPorts() ) {
-	    putPort(portEvent);
-	}
     }
 
     void removeSwitch(SwitchEvent swEvent) {
@@ -639,11 +593,6 @@
 	    throw new IllegalArgumentException("Switch cannot be null");
 	}
 
-	// TODO handle child Port event properly for performance
-	for (PortEvent portEvent : swEvent.getPorts() ) {
-	    removePort(portEvent);
-	}
-
 	Switch sw = networkGraph.getSwitch(swEvent.getDpid());
 	if (sw == null) {
 	    log.warn("Switch {} already removed, ignoring", swEvent);
@@ -1027,22 +976,39 @@
     }
 
     @Deprecated
-    public void loadWholeTopologyFromDB() {
+    private Collection<EventEntry<TopologyEvent>> readWholeTopologyFromDB() {
+	Collection<EventEntry<TopologyEvent>> collection =
+	    new LinkedList<EventEntry<TopologyEvent>>();
+
 	// XXX May need to clear whole topology first, depending on
 	// how we initially subscribe to replication events
 
+	// Add all active switches
 	for (RCSwitch sw : RCSwitch.getAllSwitches()) {
 	    if (sw.getStatus() != RCSwitch.STATUS.ACTIVE) {
 		continue;
 	    }
-	    putSwitchReplicationEvent(new SwitchEvent(sw.getDpid()));
+
+	    SwitchEvent switchEvent = new SwitchEvent(sw.getDpid());
+	    TopologyEvent topologyEvent = new TopologyEvent(switchEvent);
+	    EventEntry<TopologyEvent> eventEntry =
+		new EventEntry<TopologyEvent>(EventEntry.Type.ENTRY_ADD,
+					      topologyEvent);
+	    collection.add(eventEntry);
 	}
 
+	// Add all active ports
 	for (RCPort p : RCPort.getAllPorts()) {
 	    if (p.getStatus() != RCPort.STATUS.ACTIVE) {
 		continue;
 	    }
-	    putPortReplicationEvent(new PortEvent(p.getDpid(), p.getNumber()));
+
+	    PortEvent portEvent = new PortEvent(p.getDpid(), p.getNumber());
+	    TopologyEvent topologyEvent = new TopologyEvent(portEvent);
+	    EventEntry<TopologyEvent> eventEntry =
+		new EventEntry<TopologyEvent>(EventEntry.Type.ENTRY_ADD,
+					      topologyEvent);
+	    collection.add(eventEntry);
 	}
 
 	// TODO Is Device going to be in DB? If so, read from DB.
@@ -1062,11 +1028,19 @@
 	    if (srcPort == null || dstPort == null) {
 		continue;
 	    }
-	    putLinkReplicationEvent(new LinkEvent(l.getSrc().dpid,
-						  l.getSrc().number,
-						  l.getDst().dpid,
-						  l.getDst().number));
+
+	    LinkEvent linkEvent = new LinkEvent(l.getSrc().dpid,
+						l.getSrc().number,
+						l.getDst().dpid,
+						l.getDst().number);
+	    TopologyEvent topologyEvent = new TopologyEvent(linkEvent);
+	    EventEntry<TopologyEvent> eventEntry =
+		new EventEntry<TopologyEvent>(EventEntry.Type.ENTRY_ADD,
+					      topologyEvent);
+	    collection.add(eventEntry);
 	}
+
+	return collection;
     }
 
     @Deprecated