diff --git a/src/main/java/net/onrc/onos/apps/forwarding/Forwarding.java b/src/main/java/net/onrc/onos/apps/forwarding/Forwarding.java
index d955828..03c9740 100644
--- a/src/main/java/net/onrc/onos/apps/forwarding/Forwarding.java
+++ b/src/main/java/net/onrc/onos/apps/forwarding/Forwarding.java
@@ -560,6 +560,8 @@
                     break;
                 case STATE_CHANGED:
                     IntentState state = pathIntent.getState();
+                    log.debug("This is STATE_CHANGED. intent id {} is now state {}",
+                            pathIntent.getId() , state);
                     switch (state) {
                         case INST_REQ:
                             break;
diff --git a/src/main/java/net/onrc/onos/core/devicemanager/OnosDevice.java b/src/main/java/net/onrc/onos/core/devicemanager/OnosDevice.java
index d0a5ee4..1a2bdeb 100644
--- a/src/main/java/net/onrc/onos/core/devicemanager/OnosDevice.java
+++ b/src/main/java/net/onrc/onos/core/devicemanager/OnosDevice.java
@@ -19,9 +19,12 @@
 
 import java.io.Serializable;
 import java.util.Date;
+import java.util.Objects;
 
 import net.floodlightcontroller.util.MACAddress;
 
+
+
 /**
  * An entity on the network is a visible trace of a device that corresponds
  * to a packet received from a particular interface on the edge of a network,
@@ -53,13 +56,13 @@
      * The DPID of the switch for the ingress point for this entity,
      * or null if not present.
      */
-    private long switchDPID;
+    private Long switchDPID;
 
     /**
      * The port number of the switch for the ingress point for this entity,
      * or null if not present.
      */
-    private short switchPort;
+    private Long switchPort;
 
     /**
      * The last time we observed this entity on the network.
@@ -75,16 +78,16 @@
     }
 
     /**
-     * Create a new entity.
+     * Create a new device and its information.
      *
-     * @param macAddress
-     * @param vlan
-     * @param switchDPID
-     * @param switchPort
-     * @param lastSeenTimestamp
+     * @param macAddress mac address of this device
+     * @param vlan vlan ID of this device
+     * @param switchDPID switch DPID where the device is attached
+     * @param switchPort port number where the device is attached
+     * @param lastSeenTimestamp last packet-in time of this device
      */
     public OnosDevice(MACAddress macAddress, Short vlan, Long switchDPID,
-            short switchPort, Date lastSeenTimestamp) {
+            Long switchPort, Date lastSeenTimestamp) {
         this.macAddress = macAddress;
         this.vlan = vlan;
         this.switchDPID = switchDPID;
@@ -112,18 +115,10 @@
         return switchDPID;
     }
 
-    public void setSwitchDPID(long dpid) {
-        this.switchDPID = dpid;
-    }
-
-    public short getSwitchPort() {
+    public Long getSwitchPort() {
         return switchPort;
     }
 
-    public void setSwitchPort(short port) {
-        this.switchPort = port;
-    }
-
     public Date getLastSeenTimestamp() {
         if (this.lastSeenTimestamp == null) {
             return null;
@@ -137,14 +132,11 @@
 
     @Override
     public int hashCode() {
-        if (hashCode != 0) {
-            return hashCode;
-        }
         final int prime = 31;
         hashCode = 1;
         hashCode = prime * hashCode + (int) (macAddress.toLong() ^ (macAddress.toLong() >>> 32));
-        hashCode = prime * hashCode + (int) switchDPID;
-        hashCode = prime * hashCode + (int) switchPort;
+        hashCode = prime * hashCode + ((switchDPID == null) ? 0 : switchDPID.hashCode());
+        hashCode = prime * hashCode + ((switchPort == null) ? 0 : switchPort.hashCode());
         hashCode = prime * hashCode + ((vlan == null) ? 0 : vlan.hashCode());
         return hashCode;
     }
@@ -164,24 +156,16 @@
         if (hashCode() != other.hashCode()) {
             return false;
         }
-        if (macAddress == null) {
-            if (other.macAddress != null) {
-                return false;
-            }
-        } else if (!macAddress.equals(other.macAddress)) {
+        if (!Objects.equals(macAddress, other.macAddress)) {
             return false;
         }
-        if (switchDPID != other.switchDPID) {
+        if (!Objects.equals(switchDPID, other.switchDPID)) {
             return false;
         }
-        if (switchPort != other.switchPort) {
+        if (!Objects.equals(switchPort, other.switchPort)) {
             return false;
         }
-        if (vlan == null) {
-            if (other.vlan != null) {
-                return false;
-            }
-        } else if (!vlan.equals(other.vlan)) {
+        if (!Objects.equals(vlan, other.vlan)) {
             return false;
         }
         return true;
diff --git a/src/main/java/net/onrc/onos/core/devicemanager/OnosDeviceManager.java b/src/main/java/net/onrc/onos/core/devicemanager/OnosDeviceManager.java
index 23944a0..0c7a75e 100644
--- a/src/main/java/net/onrc/onos/core/devicemanager/OnosDeviceManager.java
+++ b/src/main/java/net/onrc/onos/core/devicemanager/OnosDeviceManager.java
@@ -8,7 +8,6 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
-import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.concurrent.Executors;
 import java.util.concurrent.ScheduledExecutorService;
@@ -24,11 +23,10 @@
 import net.floodlightcontroller.core.module.IFloodlightModule;
 import net.floodlightcontroller.core.module.IFloodlightService;
 import net.floodlightcontroller.util.MACAddress;
-import net.onrc.onos.core.datagrid.IDatagridService;
-import net.onrc.onos.core.datagrid.IEventChannel;
-import net.onrc.onos.core.datagrid.IEventChannelListener;
 import net.onrc.onos.core.packet.Ethernet;
+import net.onrc.onos.core.topology.Device;
 import net.onrc.onos.core.topology.ITopologyService;
+import net.onrc.onos.core.topology.Port;
 import net.onrc.onos.core.topology.Topology;
 
 import org.openflow.protocol.OFMessage;
@@ -39,8 +37,7 @@
 
 public class OnosDeviceManager implements IFloodlightModule,
         IOFMessageListener,
-        IOnosDeviceService,
-        IEventChannelListener<Long, OnosDevice> {
+        IOnosDeviceService {
 
     private static final Logger log = LoggerFactory.getLogger(OnosDeviceManager.class);
     private static final long DEVICE_CLEANING_INITIAL_DELAY = 30;
@@ -52,16 +49,6 @@
     private static final ScheduledExecutorService EXECUTOR_SERVICE =
             Executors.newSingleThreadScheduledExecutor();
 
-    // TODO This infrastructure maintains a global device cache in the
-    // OnosDeviceManager module on each instance (in mapDevice). We want to
-    // remove this eventually - the global cache should be maintained by the
-    // topology layer (which it currently is as well).
-    private IDatagridService datagrid;
-    private IEventChannel<Long, OnosDevice> eventChannel;
-    private static final String DEVICE_CHANNEL_NAME = "onos.device";
-    private final Map<Long, OnosDevice> mapDevice =
-            new ConcurrentHashMap<Long, OnosDevice>();
-
     private ITopologyService topologyService;
     private Topology topology;
 
@@ -129,6 +116,10 @@
     // The above "receive" method couldn't be tested
     // because of IFloodlightProviderService static final field.
     protected Command processPacketIn(IOFSwitch sw, OFPacketIn pi, Ethernet eth) {
+        if (log.isTraceEnabled()) {
+            log.trace("Receive PACKET_IN swId {}, portId {}", sw.getId(), pi.getInPort());
+        }
+
         long dpid = sw.getId();
         short portId = pi.getInPort();
         Long mac = eth.getSourceMAC().toLong();
@@ -140,31 +131,21 @@
             return Command.STOP;
         }
 
-        // We check if it is the same device in datagrid to suppress the device update
-        OnosDevice exDev = mapDevice.get(mac);
-        if (exDev != null && exDev.equals(srcDevice)) {
-            // There is the same existing device. Update only ActiveSince time.
-            // TODO This doesn't update the timestamp in the Topology module,
-            // only in the local cache in this local driver module.
-            exDev.setLastSeenTimestamp(new Date());
-            if (log.isTraceEnabled()) {
-                log.trace("In the local cache, there is the same device."
-                        + " Only update last seen time: {}", exDev);
-            }
-            return Command.CONTINUE;
-        }
-
         // If the switch port we try to attach a new device already has a link,
         // then don't add the device
         // TODO We probably don't need to check this here, it should be done in
         // the Topology module.
-        if (topology.getOutgoingLink(dpid, (long) portId) != null) {
-            if (log.isTraceEnabled()) {
-                log.trace("Stop adding OnosDevice {} as " +
-                        "there is a link on the port: dpid {} port {}",
-                        srcDevice.getMacAddress(), dpid, portId);
+        topology.acquireReadLock();
+        try {
+            if (topology.getOutgoingLink(dpid, (long) portId) != null ||
+                    topology.getIncomingLink(dpid, (long) portId) != null) {
+                log.debug("Stop adding OnosDevice {} as " +
+                    "there is a link on the port: dpid {} port {}",
+                    srcDevice.getMacAddress(), dpid, portId);
+                return Command.CONTINUE;
             }
-            return Command.CONTINUE;
+        } finally {
+            topology.releaseReadLock();
         }
 
         addOnosDevice(mac, srcDevice);
@@ -187,28 +168,30 @@
         @Override
         public void run() {
             log.debug("called CleanDevice");
+            topology.acquireReadLock();
             try {
-                Set<OnosDevice> deleteSet = new HashSet<OnosDevice>();
-                for (OnosDevice dev : mapDevice.values()) {
-                    long now = new Date().getTime();
-                    if ((now - dev.getLastSeenTimestamp().getTime()
-                            > agingMillisecConfig)) {
+                Set<Device> deleteSet = new HashSet<Device>();
+                for (Device dev : topology.getDevices()) {
+                    long now = System.currentTimeMillis();
+                    if ((now - dev.getLastSeenTime() > agingMillisecConfig)) {
                         if (log.isTraceEnabled()) {
-                            log.debug("Removing device info from the datagrid: {}, diff {}",
-                                    dev, now - dev.getLastSeenTimestamp().getTime());
+                            log.trace("Removing device info: mac {}, now {}, lastSeenTime {}, diff {}",
+                                    dev.getMacAddress(), now, dev.getLastSeenTime(), now - dev.getLastSeenTime());
                         }
                         deleteSet.add(dev);
                     }
                 }
 
-                for (OnosDevice dev : deleteSet) {
-                    deleteOnosDevice(dev);
+                for (Device dev : deleteSet) {
+                    deleteOnosDeviceByMac(dev.getMacAddress());
                 }
             } catch (Exception e) {
                 // Any exception thrown by the task will prevent the Executor
                 // from running the next iteration, so we need to catch and log
                 // all exceptions here.
                 log.error("Exception in device cleanup thread:", e);
+            } finally {
+                topology.releaseReadLock();
             }
         }
     }
@@ -223,7 +206,7 @@
      */
     protected OnosDevice getSourceDeviceFromPacket(Ethernet eth,
             long swdpid,
-            short port) {
+            long port) {
         MACAddress sourceMac = eth.getSourceMAC();
 
         // Ignore broadcast/multicast source
@@ -261,7 +244,6 @@
                 new ArrayList<Class<? extends IFloodlightService>>();
         dependencies.add(IFloodlightProviderService.class);
         dependencies.add(ITopologyService.class);
-        dependencies.add(IDatagridService.class);
         return dependencies;
     }
 
@@ -270,7 +252,6 @@
             throws FloodlightModuleException {
         floodlightProvider = context.getServiceImpl(IFloodlightProviderService.class);
         deviceListeners = new CopyOnWriteArrayList<IOnosDeviceListener>();
-        datagrid = context.getServiceImpl(IDatagridService.class);
         topologyService = context.getServiceImpl(ITopologyService.class);
         topology = topologyService.getTopology();
 
@@ -280,56 +261,48 @@
     @Override
     public void startUp(FloodlightModuleContext context) {
         floodlightProvider.addOFMessageListener(OFType.PACKET_IN, this);
-        eventChannel = datagrid.addListener(DEVICE_CHANNEL_NAME, this,
-                Long.class,
-                OnosDevice.class);
         EXECUTOR_SERVICE.scheduleAtFixedRate(new CleanDevice(),
                 DEVICE_CLEANING_INITIAL_DELAY, cleanupSecondConfig, TimeUnit.SECONDS);
     }
 
     @Override
     public void deleteOnosDevice(OnosDevice dev) {
-        Long mac = dev.getMacAddress().toLong();
-        eventChannel.removeEntry(mac);
         floodlightProvider.publishUpdate(
                 new OnosDeviceUpdate(dev, OnosDeviceUpdateType.DELETE));
     }
 
     @Override
     public void deleteOnosDeviceByMac(MACAddress mac) {
-        OnosDevice deleteDevice = mapDevice.get(mac.toLong());
-        deleteOnosDevice(deleteDevice);
+        OnosDevice deleteDevice = null;
+        topology.acquireReadLock();
+        try {
+            Device dev = topology.getDeviceByMac(mac);
+
+            for (Port switchPort : dev.getAttachmentPoints()) {
+                // We don't handle vlan now and multiple attachment points.
+                deleteDevice = new OnosDevice(dev.getMacAddress(),
+                        null,
+                        switchPort.getDpid(),
+                        switchPort.getNumber(),
+                        new Date(dev.getLastSeenTime()));
+                break;
+            }
+        } finally {
+            topology.releaseReadLock();
+        }
+
+        if (deleteDevice != null) {
+            deleteOnosDevice(deleteDevice);
+        }
     }
 
     @Override
     public void addOnosDevice(Long mac, OnosDevice dev) {
-        eventChannel.addEntry(mac, dev);
         floodlightProvider.publishUpdate(
                 new OnosDeviceUpdate(dev, OnosDeviceUpdateType.ADD));
     }
 
     @Override
-    public void entryAdded(OnosDevice dev) {
-        Long mac = dev.getMacAddress().toLong();
-        mapDevice.put(mac, dev);
-        log.debug("Device added into local Cache: device mac {}", mac);
-    }
-
-    @Override
-    public void entryRemoved(OnosDevice dev) {
-        Long mac = dev.getMacAddress().toLong();
-        mapDevice.remove(mac);
-        log.debug("Device removed into local Cache: device mac {}", mac);
-    }
-
-    @Override
-    public void entryUpdated(OnosDevice dev) {
-        Long mac = dev.getMacAddress().toLong();
-        mapDevice.put(mac, dev);
-        log.debug("Device updated into local Cache: device mac {}", mac);
-    }
-
-    @Override
     public void addOnosDeviceListener(IOnosDeviceListener listener) {
         deviceListeners.add(listener);
     }
diff --git a/src/main/java/net/onrc/onos/core/intent/runtime/PlanInstallModule.java b/src/main/java/net/onrc/onos/core/intent/runtime/PlanInstallModule.java
index b74514c..025b6d7 100644
--- a/src/main/java/net/onrc/onos/core/intent/runtime/PlanInstallModule.java
+++ b/src/main/java/net/onrc/onos/core/intent/runtime/PlanInstallModule.java
@@ -340,7 +340,8 @@
                 states.domainSwitchDpids.addAll(domainSwitchDpids);
             }
             parentIntentMap.remove(intentParentId);
-            log.debug("addEntry to intentStateChannel intentId {}, states {}", flowRemovedMsg.getCookie(), states);
+            log.debug("addEntry to intentStateChannel intentId {}, states {}",
+                    pathIntentId, newState);
 
             intentStateChannel.addTransientEntry(flowRemovedMsg.getCookie(), states);
         }
diff --git a/src/main/java/net/onrc/onos/core/topology/DeviceImpl.java b/src/main/java/net/onrc/onos/core/topology/DeviceImpl.java
index fc1628e..0ba23dd 100644
--- a/src/main/java/net/onrc/onos/core/topology/DeviceImpl.java
+++ b/src/main/java/net/onrc/onos/core/topology/DeviceImpl.java
@@ -47,19 +47,19 @@
     /**
      * Only {@link TopologyManager} should use this method.
      *
-     * @param p
+     * @param port the port that the device is attached to
      */
-    void addAttachmentPoint(Port p) {
-        this.attachmentPoints.remove(p);
-        this.attachmentPoints.addFirst(p);
+    void addAttachmentPoint(Port port) {
+        this.attachmentPoints.remove(port);
+        this.attachmentPoints.addFirst(port);
     }
 
     /**
      * Only {@link TopologyManager} should use this method.
      *
-     * @param p
+     * @param port the port that the device is attached to
      */
-    boolean removeAttachmentPoint(Port p) {
-        return this.attachmentPoints.remove(p);
+    boolean removeAttachmentPoint(Port port) {
+        return this.attachmentPoints.remove(port);
     }
 }
diff --git a/src/main/java/net/onrc/onos/core/topology/TopologyManager.java b/src/main/java/net/onrc/onos/core/topology/TopologyManager.java
index 8e0a4e6..343102b 100644
--- a/src/main/java/net/onrc/onos/core/topology/TopologyManager.java
+++ b/src/main/java/net/onrc/onos/core/topology/TopologyManager.java
@@ -1085,6 +1085,8 @@
             attachmentFound = true;
         }
 
+        deviceImpl.setLastSeenTime(deviceEvent.getLastSeenTime());
+
         // Update the device in the topology
         if (attachmentFound) {
             log.debug("Storing the device info into the Topology: mac {}", deviceEvent.getMac());
diff --git a/src/main/java/net/onrc/onos/core/topology/TopologyPublisher.java b/src/main/java/net/onrc/onos/core/topology/TopologyPublisher.java
index 36399bc..eb76c1e 100644
--- a/src/main/java/net/onrc/onos/core/topology/TopologyPublisher.java
+++ b/src/main/java/net/onrc/onos/core/topology/TopologyPublisher.java
@@ -307,8 +307,7 @@
     public void onosDeviceAdded(OnosDevice device) {
         log.debug("Called onosDeviceAdded mac {}", device.getMacAddress());
 
-        SwitchPort sp = new SwitchPort(device.getSwitchDPID(),
-                (long) device.getSwitchPort());
+        SwitchPort sp = new SwitchPort(device.getSwitchDPID(), device.getSwitchPort());
         List<SwitchPort> spLists = new ArrayList<SwitchPort>();
         spLists.add(sp);
         DeviceEvent event = new DeviceEvent(device.getMacAddress());