diff --git a/core/net/src/main/java/org/onosproject/cluster/impl/ClusterManager.java b/core/net/src/main/java/org/onosproject/cluster/impl/ClusterManager.java
index 531a6fa..df7feff 100644
--- a/core/net/src/main/java/org/onosproject/cluster/impl/ClusterManager.java
+++ b/core/net/src/main/java/org/onosproject/cluster/impl/ClusterManager.java
@@ -15,7 +15,8 @@
  */
 package org.onosproject.cluster.impl;
 
-import com.google.common.collect.Sets;
+import java.util.Set;
+import java.util.stream.Collectors;
 
 import org.apache.felix.scr.annotations.Activate;
 import org.apache.felix.scr.annotations.Component;
@@ -23,41 +24,19 @@
 import org.apache.felix.scr.annotations.Reference;
 import org.apache.felix.scr.annotations.ReferenceCardinality;
 import org.apache.felix.scr.annotations.Service;
-import org.apache.karaf.system.SystemService;
 import org.joda.time.DateTime;
 import org.onlab.packet.IpAddress;
-import org.onlab.util.Tools;
 import org.onosproject.cluster.ClusterAdminService;
-import org.onosproject.cluster.ClusterEvent;
 import org.onosproject.cluster.ClusterEventListener;
-import org.onosproject.cluster.ClusterMetadata;
-import org.onosproject.cluster.ClusterMetadataAdminService;
-import org.onosproject.cluster.ClusterMetadataDiff;
-import org.onosproject.cluster.ClusterMetadataEvent;
-import org.onosproject.cluster.ClusterMetadataEventListener;
-import org.onosproject.cluster.ClusterMetadataService;
 import org.onosproject.cluster.ClusterService;
-import org.onosproject.cluster.ClusterStore;
-import org.onosproject.cluster.ClusterStoreDelegate;
 import org.onosproject.cluster.ControllerNode;
-import org.onosproject.cluster.DefaultPartition;
+import org.onosproject.cluster.UnifiedClusterAdminService;
+import org.onosproject.cluster.UnifiedClusterService;
 import org.onosproject.cluster.NodeId;
-import org.onosproject.cluster.Partition;
-import org.onosproject.cluster.PartitionId;
 import org.onosproject.core.Version;
-import org.onosproject.event.AbstractListenerManager;
+import org.onosproject.core.VersionService;
 import org.slf4j.Logger;
 
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.Collections;
-import java.util.HashSet;
-import java.util.List;
-import java.util.Set;
-import java.util.concurrent.atomic.AtomicReference;
-
-import static com.google.common.base.Preconditions.checkArgument;
-import static com.google.common.base.Preconditions.checkNotNull;
 import static org.onosproject.security.AppGuard.checkPermission;
 import static org.onosproject.security.AppPermission.Type.CLUSTER_READ;
 import static org.slf4j.LoggerFactory.getLogger;
@@ -67,172 +46,122 @@
  */
 @Component(immediate = true)
 @Service
-public class ClusterManager
-        extends AbstractListenerManager<ClusterEvent, ClusterEventListener>
-        implements ClusterService, ClusterAdminService {
+public class ClusterManager implements ClusterService, ClusterAdminService {
 
-    public static final String INSTANCE_ID_NULL = "Instance ID cannot be null";
-    private static final int DEFAULT_PARTITION_SIZE = 3;
     private final Logger log = getLogger(getClass());
 
-    private ClusterStoreDelegate delegate = new InternalStoreDelegate();
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    private UnifiedClusterService clusterService;
 
     @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
-    protected ClusterMetadataService clusterMetadataService;
+    private UnifiedClusterAdminService clusterAdminService;
 
     @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
-    protected ClusterMetadataAdminService clusterMetadataAdminService;
+    private VersionService versionService;
 
-    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
-    protected ClusterStore store;
-
-    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
-    protected SystemService systemService;
-
-    private final AtomicReference<ClusterMetadata> currentMetadata = new AtomicReference<>();
-    private final InternalClusterMetadataListener metadataListener = new InternalClusterMetadataListener();
+    private Version version;
 
     @Activate
     public void activate() {
-        store.setDelegate(delegate);
-        eventDispatcher.addSink(ClusterEvent.class, listenerRegistry);
-        clusterMetadataService.addListener(metadataListener);
-        processMetadata(clusterMetadataService.getClusterMetadata());
+        version = versionService.version();
         log.info("Started");
     }
 
     @Deactivate
     public void deactivate() {
-        clusterMetadataService.removeListener(metadataListener);
-        store.unsetDelegate(delegate);
-        eventDispatcher.removeSink(ClusterEvent.class);
         log.info("Stopped");
     }
 
     @Override
     public ControllerNode getLocalNode() {
         checkPermission(CLUSTER_READ);
-        return store.getLocalNode();
+        return clusterService.getLocalNode();
     }
 
     @Override
     public Set<ControllerNode> getNodes() {
         checkPermission(CLUSTER_READ);
-        return store.getNodes();
+        return clusterService.getNodes()
+                .stream()
+                .filter(node -> clusterService.getVersion(node.id()).equals(version))
+                .collect(Collectors.toSet());
     }
 
     @Override
     public ControllerNode getNode(NodeId nodeId) {
         checkPermission(CLUSTER_READ);
-        checkNotNull(nodeId, INSTANCE_ID_NULL);
-        return store.getNode(nodeId);
+        Version nodeVersion = clusterService.getVersion(nodeId);
+        if (nodeVersion != null && nodeVersion.equals(version)) {
+            return clusterService.getNode(nodeId);
+        }
+        return null;
     }
 
     @Override
     public ControllerNode.State getState(NodeId nodeId) {
         checkPermission(CLUSTER_READ);
-        checkNotNull(nodeId, INSTANCE_ID_NULL);
-        return store.getState(nodeId);
+        Version nodeVersion = clusterService.getVersion(nodeId);
+        if (nodeVersion != null && nodeVersion.equals(version)) {
+            return clusterService.getState(nodeId);
+        }
+        return null;
     }
 
     @Override
     public Version getVersion(NodeId nodeId) {
         checkPermission(CLUSTER_READ);
-        checkNotNull(nodeId, INSTANCE_ID_NULL);
-        return store.getVersion(nodeId);
+        Version nodeVersion = clusterService.getVersion(nodeId);
+        if (nodeVersion != null && nodeVersion.equals(version)) {
+            return nodeVersion;
+        }
+        return null;
     }
 
     @Override
     public void markFullyStarted(boolean started) {
-        store.markFullyStarted(started);
+        clusterAdminService.markFullyStarted(started);
     }
 
     @Override
     public DateTime getLastUpdated(NodeId nodeId) {
         checkPermission(CLUSTER_READ);
-        return store.getLastUpdated(nodeId);
+        Version nodeVersion = clusterService.getVersion(nodeId);
+        if (nodeVersion != null && nodeVersion.equals(version)) {
+            return clusterService.getLastUpdated(nodeId);
+        }
+        return null;
     }
 
     @Override
     public void formCluster(Set<ControllerNode> nodes) {
-        formCluster(nodes, DEFAULT_PARTITION_SIZE);
+        clusterAdminService.formCluster(nodes);
     }
 
     @Override
     public void formCluster(Set<ControllerNode> nodes, int partitionSize) {
-        checkNotNull(nodes, "Nodes cannot be null");
-        checkArgument(!nodes.isEmpty(), "Nodes cannot be empty");
-
-        ClusterMetadata metadata = new ClusterMetadata("default", nodes, buildDefaultPartitions(nodes, partitionSize));
-        clusterMetadataAdminService.setClusterMetadata(metadata);
-        try {
-            log.warn("Shutting down container for cluster reconfiguration!");
-            // Clean up persistent state associated with previous cluster configuration.
-            Tools.removeDirectory(System.getProperty("karaf.data") + "/partitions");
-            systemService.reboot("now", SystemService.Swipe.NONE);
-        } catch (Exception e) {
-            log.error("Unable to reboot container", e);
-        }
+        clusterAdminService.formCluster(nodes, partitionSize);
     }
 
     @Override
     public ControllerNode addNode(NodeId nodeId, IpAddress ip, int tcpPort) {
-        checkNotNull(nodeId, INSTANCE_ID_NULL);
-        checkNotNull(ip, "IP address cannot be null");
-        checkArgument(tcpPort > 5000, "TCP port must be > 5000");
-        return store.addNode(nodeId, ip, tcpPort);
+        return clusterAdminService.addNode(nodeId, ip, tcpPort);
     }
 
     @Override
     public void removeNode(NodeId nodeId) {
-        checkNotNull(nodeId, INSTANCE_ID_NULL);
-        store.removeNode(nodeId);
-    }
-
-    // Store delegate to re-post events emitted from the store.
-    private class InternalStoreDelegate implements ClusterStoreDelegate {
-        @Override
-        public void notify(ClusterEvent event) {
-            post(event);
+        Version nodeVersion = clusterService.getVersion(nodeId);
+        if (nodeVersion != null && nodeVersion.equals(version)) {
+            clusterAdminService.removeNode(nodeId);
         }
     }
 
-    private static Set<Partition> buildDefaultPartitions(Collection<ControllerNode> nodes, int partitionSize) {
-        List<ControllerNode> sorted = new ArrayList<>(nodes);
-        Collections.sort(sorted, (o1, o2) -> o1.id().toString().compareTo(o2.id().toString()));
-        Set<Partition> partitions = Sets.newHashSet();
-        // add partitions
-        int length = nodes.size();
-        int count = Math.min(partitionSize, length);
-        for (int i = 0; i < length; i++) {
-            int index = i;
-            Set<NodeId> set = new HashSet<>(count);
-            for (int j = 0; j < count; j++) {
-                set.add(sorted.get((i + j) % length).id());
-            }
-            partitions.add(new DefaultPartition(PartitionId.from((index + 1)), set));
-        }
-        return partitions;
+    @Override
+    public void addListener(ClusterEventListener listener) {
+        clusterService.addListener(listener);
     }
 
-    /**
-     * Processes metadata by adding and removing nodes from the cluster.
-     */
-    private synchronized void processMetadata(ClusterMetadata metadata) {
-        try {
-            ClusterMetadataDiff examiner =
-                    new ClusterMetadataDiff(currentMetadata.get(), metadata);
-            examiner.nodesAdded().forEach(node -> addNode(node.id(), node.ip(), node.tcpPort()));
-            examiner.nodesRemoved().forEach(this::removeNode);
-        } finally {
-            currentMetadata.set(metadata);
-        }
-    }
-
-    private class InternalClusterMetadataListener implements ClusterMetadataEventListener {
-        @Override
-        public void event(ClusterMetadataEvent event) {
-            processMetadata(event.subject());
-        }
+    @Override
+    public void removeListener(ClusterEventListener listener) {
+        clusterService.removeListener(listener);
     }
 }
diff --git a/core/net/src/main/java/org/onosproject/cluster/impl/UnifiedClusterManager.java b/core/net/src/main/java/org/onosproject/cluster/impl/UnifiedClusterManager.java
new file mode 100644
index 0000000..3617305
--- /dev/null
+++ b/core/net/src/main/java/org/onosproject/cluster/impl/UnifiedClusterManager.java
@@ -0,0 +1,237 @@
+/*
+ * Copyright 2014-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.cluster.impl;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import java.util.concurrent.atomic.AtomicReference;
+
+import com.google.common.collect.Sets;
+import org.apache.felix.scr.annotations.Activate;
+import org.apache.felix.scr.annotations.Component;
+import org.apache.felix.scr.annotations.Deactivate;
+import org.apache.felix.scr.annotations.Reference;
+import org.apache.felix.scr.annotations.ReferenceCardinality;
+import org.apache.felix.scr.annotations.Service;
+import org.apache.karaf.system.SystemService;
+import org.joda.time.DateTime;
+import org.onlab.packet.IpAddress;
+import org.onlab.util.Tools;
+import org.onosproject.cluster.ClusterEvent;
+import org.onosproject.cluster.ClusterEventListener;
+import org.onosproject.cluster.ClusterMetadata;
+import org.onosproject.cluster.ClusterMetadataAdminService;
+import org.onosproject.cluster.ClusterMetadataDiff;
+import org.onosproject.cluster.ClusterMetadataEvent;
+import org.onosproject.cluster.ClusterMetadataEventListener;
+import org.onosproject.cluster.ClusterMetadataService;
+import org.onosproject.cluster.ClusterStore;
+import org.onosproject.cluster.ClusterStoreDelegate;
+import org.onosproject.cluster.ControllerNode;
+import org.onosproject.cluster.DefaultPartition;
+import org.onosproject.cluster.UnifiedClusterAdminService;
+import org.onosproject.cluster.UnifiedClusterService;
+import org.onosproject.cluster.NodeId;
+import org.onosproject.cluster.Partition;
+import org.onosproject.cluster.PartitionId;
+import org.onosproject.core.Version;
+import org.onosproject.event.AbstractListenerManager;
+import org.slf4j.Logger;
+
+import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.base.Preconditions.checkNotNull;
+import static org.onosproject.security.AppGuard.checkPermission;
+import static org.onosproject.security.AppPermission.Type.CLUSTER_READ;
+import static org.slf4j.LoggerFactory.getLogger;
+
+/**
+ * Implementation of the cluster service.
+ */
+@Component(immediate = true)
+@Service
+public class UnifiedClusterManager
+        extends AbstractListenerManager<ClusterEvent, ClusterEventListener>
+        implements UnifiedClusterService, UnifiedClusterAdminService {
+
+    public static final String INSTANCE_ID_NULL = "Instance ID cannot be null";
+    private static final int DEFAULT_PARTITION_SIZE = 3;
+    private final Logger log = getLogger(getClass());
+
+    private ClusterStoreDelegate delegate = new InternalStoreDelegate();
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected ClusterMetadataService clusterMetadataService;
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected ClusterMetadataAdminService clusterMetadataAdminService;
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected ClusterStore store;
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected SystemService systemService;
+
+    private final AtomicReference<ClusterMetadata> currentMetadata = new AtomicReference<>();
+    private final InternalClusterMetadataListener metadataListener = new InternalClusterMetadataListener();
+
+    @Activate
+    public void activate() {
+        store.setDelegate(delegate);
+        eventDispatcher.addSink(ClusterEvent.class, listenerRegistry);
+        clusterMetadataService.addListener(metadataListener);
+        processMetadata(clusterMetadataService.getClusterMetadata());
+        log.info("Started");
+    }
+
+    @Deactivate
+    public void deactivate() {
+        clusterMetadataService.removeListener(metadataListener);
+        store.unsetDelegate(delegate);
+        eventDispatcher.removeSink(ClusterEvent.class);
+        log.info("Stopped");
+    }
+
+    @Override
+    public ControllerNode getLocalNode() {
+        checkPermission(CLUSTER_READ);
+        return store.getLocalNode();
+    }
+
+    @Override
+    public Set<ControllerNode> getNodes() {
+        checkPermission(CLUSTER_READ);
+        return store.getNodes();
+    }
+
+    @Override
+    public ControllerNode getNode(NodeId nodeId) {
+        checkPermission(CLUSTER_READ);
+        checkNotNull(nodeId, INSTANCE_ID_NULL);
+        return store.getNode(nodeId);
+    }
+
+    @Override
+    public ControllerNode.State getState(NodeId nodeId) {
+        checkPermission(CLUSTER_READ);
+        checkNotNull(nodeId, INSTANCE_ID_NULL);
+        return store.getState(nodeId);
+    }
+
+    @Override
+    public Version getVersion(NodeId nodeId) {
+        checkPermission(CLUSTER_READ);
+        checkNotNull(nodeId, INSTANCE_ID_NULL);
+        return store.getVersion(nodeId);
+    }
+
+    @Override
+    public void markFullyStarted(boolean started) {
+        store.markFullyStarted(started);
+    }
+
+    @Override
+    public DateTime getLastUpdated(NodeId nodeId) {
+        checkPermission(CLUSTER_READ);
+        return store.getLastUpdated(nodeId);
+    }
+
+    @Override
+    public void formCluster(Set<ControllerNode> nodes) {
+        formCluster(nodes, DEFAULT_PARTITION_SIZE);
+    }
+
+    @Override
+    public void formCluster(Set<ControllerNode> nodes, int partitionSize) {
+        checkNotNull(nodes, "Nodes cannot be null");
+        checkArgument(!nodes.isEmpty(), "Nodes cannot be empty");
+
+        ClusterMetadata metadata = new ClusterMetadata("default", nodes, buildDefaultPartitions(nodes, partitionSize));
+        clusterMetadataAdminService.setClusterMetadata(metadata);
+        try {
+            log.warn("Shutting down container for cluster reconfiguration!");
+            // Clean up persistent state associated with previous cluster configuration.
+            Tools.removeDirectory(System.getProperty("karaf.data") + "/partitions");
+            systemService.reboot("now", SystemService.Swipe.NONE);
+        } catch (Exception e) {
+            log.error("Unable to reboot container", e);
+        }
+    }
+
+    @Override
+    public ControllerNode addNode(NodeId nodeId, IpAddress ip, int tcpPort) {
+        checkNotNull(nodeId, INSTANCE_ID_NULL);
+        checkNotNull(ip, "IP address cannot be null");
+        checkArgument(tcpPort > 5000, "TCP port must be > 5000");
+        return store.addNode(nodeId, ip, tcpPort);
+    }
+
+    @Override
+    public void removeNode(NodeId nodeId) {
+        checkNotNull(nodeId, INSTANCE_ID_NULL);
+        store.removeNode(nodeId);
+    }
+
+    // Store delegate to re-post events emitted from the store.
+    private class InternalStoreDelegate implements ClusterStoreDelegate {
+        @Override
+        public void notify(ClusterEvent event) {
+            post(event);
+        }
+    }
+
+    private static Set<Partition> buildDefaultPartitions(Collection<ControllerNode> nodes, int partitionSize) {
+        List<ControllerNode> sorted = new ArrayList<>(nodes);
+        Collections.sort(sorted, (o1, o2) -> o1.id().toString().compareTo(o2.id().toString()));
+        Set<Partition> partitions = Sets.newHashSet();
+        // add partitions
+        int length = nodes.size();
+        int count = Math.min(partitionSize, length);
+        for (int i = 0; i < length; i++) {
+            int index = i;
+            Set<NodeId> set = new HashSet<>(count);
+            for (int j = 0; j < count; j++) {
+                set.add(sorted.get((i + j) % length).id());
+            }
+            partitions.add(new DefaultPartition(PartitionId.from((index + 1)), set));
+        }
+        return partitions;
+    }
+
+    /**
+     * Processes metadata by adding and removing nodes from the cluster.
+     */
+    private synchronized void processMetadata(ClusterMetadata metadata) {
+        try {
+            ClusterMetadataDiff examiner =
+                    new ClusterMetadataDiff(currentMetadata.get(), metadata);
+            examiner.nodesAdded().forEach(node -> addNode(node.id(), node.ip(), node.tcpPort()));
+            examiner.nodesRemoved().forEach(this::removeNode);
+        } finally {
+            currentMetadata.set(metadata);
+        }
+    }
+
+    private class InternalClusterMetadataListener implements ClusterMetadataEventListener {
+        @Override
+        public void event(ClusterMetadataEvent event) {
+            processMetadata(event.subject());
+        }
+    }
+}
diff --git a/core/net/src/main/java/org/onosproject/core/impl/VersionManager.java b/core/net/src/main/java/org/onosproject/core/impl/VersionManager.java
index e734f7d..12210a9 100644
--- a/core/net/src/main/java/org/onosproject/core/impl/VersionManager.java
+++ b/core/net/src/main/java/org/onosproject/core/impl/VersionManager.java
@@ -54,6 +54,7 @@
             // version file not found, using default
             log.trace("Version file not found", e);
         }
+        log.info("Started");
     }
 
     @Override
diff --git a/core/net/src/main/java/org/onosproject/net/device/impl/DeviceManager.java b/core/net/src/main/java/org/onosproject/net/device/impl/DeviceManager.java
index d2b2536..bbf6d39 100644
--- a/core/net/src/main/java/org/onosproject/net/device/impl/DeviceManager.java
+++ b/core/net/src/main/java/org/onosproject/net/device/impl/DeviceManager.java
@@ -463,7 +463,7 @@
 
             // isReachable but was not MASTER or STANDBY, get a role and apply
             // Note: NONE triggers request to MastershipService
-            reassertRole(deviceId, NONE);
+            reassertRole(deviceId, mastershipService.getLocalRole(deviceId));
         }
     }
 
@@ -819,49 +819,32 @@
     private void reassertRole(final DeviceId did,
                               final MastershipRole nextRole) {
 
-        MastershipRole myNextRole = nextRole;
-        if (myNextRole == NONE) {
-            try {
-                mastershipService.requestRoleFor(did).get();
-                MastershipTerm term = termService.getMastershipTerm(did);
-                if (term != null && localNodeId.equals(term.master())) {
-                    myNextRole = MASTER;
-                } else {
-                    myNextRole = STANDBY;
-                }
-            } catch (InterruptedException e) {
-                Thread.currentThread().interrupt();
-                log.error("Interrupted waiting for Mastership", e);
-            } catch (ExecutionException e) {
-                log.error("Encountered an error waiting for Mastership", e);
-            }
-        }
-
-        switch (myNextRole) {
+        switch (nextRole) {
             case MASTER:
                 final Device device = getDevice(did);
                 if ((device != null) && !isAvailable(did)) {
                     store.markOnline(did);
                 }
                 // TODO: should apply role only if there is mismatch
-                log.debug("Applying role {} to {}", myNextRole, did);
+                log.debug("Applying role {} to {}", nextRole, did);
                 if (!applyRoleAndProbe(did, MASTER)) {
-                    log.warn("Unsuccessful applying role {} to {}", myNextRole, did);
+                    log.warn("Unsuccessful applying role {} to {}", nextRole, did);
                     // immediately failed to apply role
                     mastershipService.relinquishMastership(did);
                     // FIXME disconnect?
                 }
                 break;
             case STANDBY:
-                log.debug("Applying role {} to {}", myNextRole, did);
+                log.debug("Applying role {} to {}", nextRole, did);
                 if (!applyRoleAndProbe(did, STANDBY)) {
-                    log.warn("Unsuccessful applying role {} to {}", myNextRole, did);
+                    log.warn("Unsuccessful applying role {} to {}", nextRole, did);
                     // immediately failed to apply role
                     mastershipService.relinquishMastership(did);
                     // FIXME disconnect?
                 }
                 break;
             case NONE:
+                break;
             default:
                 // should never reach here
                 log.error("You didn't see anything. I did not exist.");
diff --git a/core/net/src/main/java/org/onosproject/upgrade/impl/UpgradeManager.java b/core/net/src/main/java/org/onosproject/upgrade/impl/UpgradeManager.java
new file mode 100644
index 0000000..ce55eda
--- /dev/null
+++ b/core/net/src/main/java/org/onosproject/upgrade/impl/UpgradeManager.java
@@ -0,0 +1,397 @@
+/*
+ * Copyright 2017-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.upgrade.impl;
+
+import java.util.Objects;
+import java.util.concurrent.atomic.AtomicReference;
+
+import org.apache.felix.scr.annotations.Activate;
+import org.apache.felix.scr.annotations.Component;
+import org.apache.felix.scr.annotations.Deactivate;
+import org.apache.felix.scr.annotations.Reference;
+import org.apache.felix.scr.annotations.ReferenceCardinality;
+import org.apache.felix.scr.annotations.Service;
+import org.onosproject.cluster.ControllerNode;
+import org.onosproject.cluster.UnifiedClusterService;
+import org.onosproject.core.Version;
+import org.onosproject.core.VersionService;
+import org.onosproject.event.AbstractListenerManager;
+import org.onosproject.store.serializers.KryoNamespaces;
+import org.onosproject.store.service.AtomicValue;
+import org.onosproject.store.service.AtomicValueEvent;
+import org.onosproject.store.service.AtomicValueEventListener;
+import org.onosproject.store.service.CoordinationService;
+import org.onosproject.store.service.Serializer;
+import org.onosproject.upgrade.Upgrade;
+import org.onosproject.upgrade.UpgradeAdminService;
+import org.onosproject.upgrade.UpgradeEvent;
+import org.onosproject.upgrade.UpgradeEventListener;
+import org.onosproject.upgrade.UpgradeService;
+import org.slf4j.Logger;
+
+import static org.slf4j.LoggerFactory.getLogger;
+
+/**
+ * Upgrade service implementation.
+ * <p>
+ * This implementation uses the {@link CoordinationService} to store upgrade state in a version-agnostic primitive.
+ * Upgrade state can be seen by current and future version nodes.
+ */
+@Component(immediate = true)
+@Service
+public class UpgradeManager
+        extends AbstractListenerManager<UpgradeEvent, UpgradeEventListener>
+        implements UpgradeService, UpgradeAdminService {
+
+    private final Logger log = getLogger(getClass());
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected VersionService versionService;
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected CoordinationService coordinationService;
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected UnifiedClusterService clusterService;
+
+    private Version localVersion;
+    private AtomicValue<Upgrade> state;
+    private final AtomicReference<Upgrade> currentState = new AtomicReference<>();
+    private final AtomicValueEventListener<Upgrade> stateListener = event -> handleChange(event);
+
+    @Activate
+    public void activate() {
+        state = coordinationService.<Upgrade>atomicValueBuilder()
+                .withName("onos-upgrade-state")
+                .withSerializer(Serializer.using(KryoNamespaces.API))
+                .build()
+                .asAtomicValue();
+        localVersion = versionService.version();
+
+        currentState.set(state.get());
+        if (currentState.get() == null) {
+            currentState.set(new Upgrade(localVersion, localVersion, Upgrade.Status.INACTIVE));
+            state.set(currentState.get());
+        }
+
+        Upgrade upgrade = currentState.get();
+
+        // If the upgrade state is not initialized, ensure this node matches the version of the cluster.
+        if (!upgrade.status().active() && !Objects.equals(upgrade.source(), localVersion)) {
+            log.error("Node version {} inconsistent with cluster version {}", localVersion, upgrade.source());
+            throw new IllegalStateException("Node version " + localVersion +
+                    " inconsistent with cluster version " + upgrade.source());
+        }
+
+        // If the upgrade state is initialized then check the node version.
+        if (upgrade.status() == Upgrade.Status.INITIALIZED) {
+            // If the source version equals the target version, attempt to update the target version.
+            if (Objects.equals(upgrade.source(), upgrade.target()) && !Objects.equals(upgrade.target(), localVersion)) {
+                upgrade = new Upgrade(upgrade.source(), localVersion, upgrade.status());
+                currentState.set(upgrade);
+                state.set(upgrade);
+            }
+        }
+
+        // If the upgrade status is active, verify that the local version matches the upgrade version.
+        if (upgrade.status().active() && !Objects.equals(upgrade.source(), upgrade.target())) {
+            // If the upgrade source/target are not equal, validate that the node's version is consistent
+            // with versions in the upgrade. There are two possibilities: that a not-yet-upgraded node is being
+            // restarted, or that a node has been upgraded, so we need to check that this node is running either
+            // the source or target version.
+            if (!Objects.equals(localVersion, upgrade.source()) && !Objects.equals(localVersion, upgrade.target())) {
+                log.error("Cannot upgrade node to version {}; Upgrade to {} already in progress",
+                        localVersion, upgrade.target());
+                throw new IllegalStateException("Cannot upgrade node to version " + localVersion + "; Upgrade to " +
+                        upgrade.target() + " already in progress");
+            }
+        }
+
+        state.addListener(stateListener);
+        log.info("Started");
+    }
+
+    @Deactivate
+    public void deactivate() {
+        state.removeListener(stateListener);
+        log.info("Stopped");
+    }
+
+    @Override
+    public boolean isUpgrading() {
+        return getState().status().active();
+    }
+
+    @Override
+    public Upgrade getState() {
+        return currentState.get();
+    }
+
+    @Override
+    public Version getVersion() {
+        Upgrade upgrade = currentState.get();
+        return upgrade.status().upgraded()
+                ? upgrade.target()
+                : upgrade.source();
+    }
+
+    @Override
+    public boolean isLocalActive() {
+        return localVersion.equals(getVersion());
+    }
+
+    @Override
+    public boolean isLocalUpgraded() {
+        Upgrade upgrade = currentState.get();
+        return upgrade.status().active()
+                && !upgrade.source().equals(upgrade.target())
+                && localVersion.equals(upgrade.target());
+    }
+
+    @Override
+    public void initialize() {
+        Upgrade inactive = currentState.get();
+
+        // If the current upgrade status is active, fail initialization.
+        if (inactive.status().active()) {
+            throw new IllegalStateException("Upgrade already active");
+        }
+
+        // Set the upgrade status to INITIALIZING.
+        Upgrade initializing = new Upgrade(
+                localVersion,
+                localVersion,
+                Upgrade.Status.INITIALIZING);
+        if (!state.compareAndSet(inactive, initializing)) {
+            throw new IllegalStateException("Concurrent upgrade modification");
+        } else {
+            currentState.set(initializing);
+
+            // Set the upgrade status to INITIALIZED.
+            Upgrade initialized = new Upgrade(
+                    initializing.source(),
+                    initializing.target(),
+                    Upgrade.Status.INITIALIZED);
+            if (!state.compareAndSet(initializing, initialized)) {
+                throw new IllegalStateException("Concurrent upgrade modification");
+            } else {
+                currentState.set(initialized);
+            }
+        }
+    }
+
+    @Override
+    public void upgrade() {
+        Upgrade initialized = currentState.get();
+
+        // If the current upgrade status is not INITIALIZED, throw an exception.
+        if (initialized.status() != Upgrade.Status.INITIALIZED) {
+            throw new IllegalStateException("Upgrade not initialized");
+        }
+
+        // Set the upgrade status to UPGRADING.
+        Upgrade upgrading = new Upgrade(
+                initialized.source(),
+                initialized.target(),
+                Upgrade.Status.UPGRADING);
+        if (!state.compareAndSet(initialized, upgrading)) {
+            throw new IllegalStateException("Concurrent upgrade modification");
+        } else {
+            currentState.set(upgrading);
+
+            // Set the upgrade status to UPGRADED.
+            Upgrade upgraded = new Upgrade(
+                    upgrading.source(),
+                    upgrading.target(),
+                    Upgrade.Status.UPGRADED);
+            if (!state.compareAndSet(upgrading, upgraded)) {
+                throw new IllegalStateException("Concurrent upgrade modification");
+            } else {
+                currentState.set(upgraded);
+            }
+        }
+    }
+
+    @Override
+    public void commit() {
+        Upgrade upgraded = currentState.get();
+
+        // If the current upgrade status is not UPGRADED, throw an exception.
+        if (upgraded.status() != Upgrade.Status.UPGRADED) {
+            throw new IllegalStateException("Upgrade not performed");
+        }
+
+        // Determine whether any nodes have not been upgraded to the target version.
+        boolean upgradeComplete = clusterService.getNodes()
+                .stream()
+                .allMatch(node -> {
+                    ControllerNode.State state = clusterService.getState(node.id());
+                    Version version = clusterService.getVersion(node.id());
+                    return state.isActive() && version != null && version.equals(upgraded.target());
+                });
+
+        // If some nodes have not yet been upgraded, throw an exception.
+        if (!upgradeComplete) {
+            throw new IllegalStateException("Some nodes have not yet been upgraded to version " + upgraded.target());
+        }
+
+        // Set the upgrade status to COMMITTING.
+        Upgrade committing = new Upgrade(
+                upgraded.source(),
+                upgraded.target(),
+                Upgrade.Status.COMMITTING);
+        if (!state.compareAndSet(upgraded, committing)) {
+            throw new IllegalStateException("Concurrent upgrade modification");
+        } else {
+            currentState.set(committing);
+
+            // Set the upgrade status to COMMITTED.
+            Upgrade committed = new Upgrade(
+                    committing.source(),
+                    committing.target(),
+                    Upgrade.Status.COMMITTED);
+            if (!state.compareAndSet(committing, committed)) {
+                throw new IllegalStateException("Concurrent upgrade modification");
+            } else {
+                currentState.set(committed);
+
+                // Set the upgrade status to INACTIVE.
+                Upgrade inactive = new Upgrade(
+                        localVersion,
+                        localVersion,
+                        Upgrade.Status.INACTIVE);
+                if (!state.compareAndSet(committed, inactive)) {
+                    throw new IllegalStateException("Concurrent upgrade modification");
+                } else {
+                    currentState.set(inactive);
+                }
+            }
+        }
+    }
+
+    @Override
+    public void rollback() {
+        Upgrade upgraded = currentState.get();
+
+        // If the current upgrade status is not UPGRADED, throw an exception.
+        if (upgraded.status() != Upgrade.Status.UPGRADED) {
+            throw new IllegalStateException("Upgrade not performed");
+        }
+
+        // Set the upgrade status to ROLLING_BACK.
+        Upgrade rollingBack = new Upgrade(
+                upgraded.source(),
+                upgraded.target(),
+                Upgrade.Status.ROLLING_BACK);
+        if (!state.compareAndSet(upgraded, rollingBack)) {
+            throw new IllegalStateException("Concurrent upgrade modification");
+        } else {
+            currentState.set(rollingBack);
+
+            // Set the upgrade status to ROLLED_BACK.
+            Upgrade rolledBack = new Upgrade(
+                    rollingBack.source(),
+                    rollingBack.target(),
+                    Upgrade.Status.ROLLED_BACK);
+            if (!state.compareAndSet(rollingBack, rolledBack)) {
+                throw new IllegalStateException("Concurrent upgrade modification");
+            } else {
+                currentState.set(rolledBack);
+            }
+        }
+    }
+
+    @Override
+    public void reset() {
+        Upgrade upgraded = currentState.get();
+
+        // If the current upgrade status is not INITIALIZED or ROLLED_BACK, throw an exception.
+        if (upgraded.status() != Upgrade.Status.INITIALIZED
+                && upgraded.status() != Upgrade.Status.ROLLED_BACK) {
+            throw new IllegalStateException("Upgrade not rolled back");
+        }
+
+        // Determine whether any nodes are still running the target version.
+        boolean rollbackComplete = clusterService.getNodes()
+                .stream()
+                .allMatch(node -> {
+                    ControllerNode.State state = clusterService.getState(node.id());
+                    Version version = clusterService.getVersion(node.id());
+                    return state.isActive() && version != null && version.equals(upgraded.source());
+                });
+
+        // If some nodes have not yet been downgraded, throw an exception.
+        if (!rollbackComplete) {
+            throw new IllegalStateException("Some nodes have not yet been downgraded to version " + upgraded.source());
+        }
+
+        // Set the upgrade status to RESETTING.
+        Upgrade resetting = new Upgrade(
+                upgraded.source(),
+                upgraded.target(),
+                Upgrade.Status.RESETTING);
+        if (!state.compareAndSet(upgraded, resetting)) {
+            throw new IllegalStateException("Concurrent upgrade modification");
+        } else {
+            currentState.set(resetting);
+
+            // Set the upgrade status to RESET.
+            Upgrade reset = new Upgrade(
+                    resetting.source(),
+                    resetting.target(),
+                    Upgrade.Status.RESET);
+            if (!state.compareAndSet(resetting, reset)) {
+                throw new IllegalStateException("Concurrent upgrade modification");
+            } else {
+                currentState.set(reset);
+
+                // Set the upgrade status to INACTIVE.
+                Upgrade inactive = new Upgrade(
+                        localVersion,
+                        localVersion,
+                        Upgrade.Status.INACTIVE);
+                if (!state.compareAndSet(reset, inactive)) {
+                    throw new IllegalStateException("Concurrent upgrade modification");
+                } else {
+                    currentState.set(inactive);
+                }
+            }
+        }
+    }
+
+    private void handleChange(AtomicValueEvent<Upgrade> event) {
+        currentState.set(event.newValue());
+        switch (event.newValue().status()) {
+            case INITIALIZED:
+                post(new UpgradeEvent(UpgradeEvent.Type.INITIALIZED, event.newValue()));
+                break;
+            case UPGRADED:
+                post(new UpgradeEvent(UpgradeEvent.Type.UPGRADED, event.newValue()));
+                break;
+            case COMMITTED:
+                post(new UpgradeEvent(UpgradeEvent.Type.COMMITTED, event.newValue()));
+                break;
+            case ROLLED_BACK:
+                post(new UpgradeEvent(UpgradeEvent.Type.ROLLED_BACK, event.newValue()));
+                break;
+            case RESET:
+                post(new UpgradeEvent(UpgradeEvent.Type.RESET, event.newValue()));
+                break;
+            default:
+                break;
+        }
+    }
+}
diff --git a/core/net/src/main/java/org/onosproject/upgrade/impl/package-info.java b/core/net/src/main/java/org/onosproject/upgrade/impl/package-info.java
new file mode 100644
index 0000000..013c93a
--- /dev/null
+++ b/core/net/src/main/java/org/onosproject/upgrade/impl/package-info.java
@@ -0,0 +1,20 @@
+/*
+ * Copyright 2017-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * Software upgrade management.
+ */
+package org.onosproject.upgrade.impl;