diff --git a/core/api/src/main/java/org/onosproject/cluster/ClusterAdminService.java b/core/api/src/main/java/org/onosproject/cluster/ClusterAdminService.java
index 625183a..e680877 100644
--- a/core/api/src/main/java/org/onosproject/cluster/ClusterAdminService.java
+++ b/core/api/src/main/java/org/onosproject/cluster/ClusterAdminService.java
@@ -15,56 +15,14 @@
  */
 package org.onosproject.cluster;
 
-import org.onlab.packet.IpAddress;
-
-import java.util.Set;
-
 /**
  * Service for administering the cluster node membership.
+ * <p>
+ * This service has a view of the cluster membership that is isolated to the local node's version during upgrades.
+ * For an equivalent service that has control over all nodes during an upgrade use
+ * {@link UnifiedClusterAdminService}.
+ *
+ * @see UnifiedClusterAdminService
  */
-public interface ClusterAdminService extends ClusterService {
-
-    /**
-     * Forms cluster configuration based on the specified set of node
-     * information.&nbsp; This method resets and restarts the controller
-     * instance.
-     *
-     * @param nodes    set of nodes that form the cluster
-     */
-    void formCluster(Set<ControllerNode> nodes);
-
-    /**
-     * Forms cluster configuration based on the specified set of node
-     * information.&nbsp; This method resets and restarts the controller
-     * instance.
-     *
-     * @param nodes    set of nodes that form the cluster
-     * @param partitionSize number of nodes to compose a partition
-     */
-    void formCluster(Set<ControllerNode> nodes, int partitionSize);
-
-    /**
-     * Adds a new controller node to the cluster.
-     *
-     * @param nodeId  controller node identifier
-     * @param ip      node IP listen address
-     * @param tcpPort tcp listen port
-     * @return newly added node
-     */
-    ControllerNode addNode(NodeId nodeId, IpAddress ip, int tcpPort);
-
-    /**
-     * Removes the specified node from the cluster node list.
-     *
-     * @param nodeId controller node identifier
-     */
-    void removeNode(NodeId nodeId);
-
-    /**
-     * Marks the current node as fully started or not.
-     *
-     * @param started true indicates all components have been started
-     */
-    void markFullyStarted(boolean started);
-
+public interface ClusterAdminService extends MembershipAdminService {
 }
diff --git a/core/api/src/main/java/org/onosproject/cluster/ClusterService.java b/core/api/src/main/java/org/onosproject/cluster/ClusterService.java
index 964357f..f17e4d9 100644
--- a/core/api/src/main/java/org/onosproject/cluster/ClusterService.java
+++ b/core/api/src/main/java/org/onosproject/cluster/ClusterService.java
@@ -15,65 +15,13 @@
  */
 package org.onosproject.cluster;
 
-import java.util.Set;
-
-import org.joda.time.DateTime;
-import org.onosproject.core.Version;
-import org.onosproject.event.ListenerService;
-
 /**
- * Service for obtaining information about the individual nodes within
- * the controller cluster.
+ * Service for obtaining information about the individual nodes within the controller cluster.
+ * <p>
+ * This service's view of the nodes in the cluster is isolated to a single version of the software. During upgrades,
+ * when multiple versions of the software are running in the same cluster, users of this service will only be able
+ * to see nodes running the same version as the local node. This is useful for limiting communication to nodes running
+ * the same version of the software.
  */
-public interface ClusterService
-    extends ListenerService<ClusterEvent, ClusterEventListener> {
-
-    /**
-     * Returns the local controller node.
-     *
-     * @return local controller node
-     */
-    ControllerNode getLocalNode();
-
-    /**
-     * Returns the set of current cluster members.
-     *
-     * @return set of cluster members
-     */
-    Set<ControllerNode> getNodes();
-
-    /**
-     * Returns the specified controller node.
-     *
-     * @param nodeId controller node identifier
-     * @return controller node
-     */
-    ControllerNode getNode(NodeId nodeId);
-
-    /**
-     * Returns the availability state of the specified controller node. Note
-     * that this does not imply that all the core and application components
-     * have been fully activated; only that the node has joined the cluster.
-     *
-     * @param nodeId controller node identifier
-     * @return availability state
-     */
-    ControllerNode.State getState(NodeId nodeId);
-
-    /**
-     * Returns the version of the given controller node.
-     *
-     * @param nodeId controller node identifier
-     * @return controller version
-     */
-    Version getVersion(NodeId nodeId);
-
-    /**
-     * Returns the system time when the availability state was last updated.
-     *
-     * @param nodeId controller node identifier
-     * @return system time when the availability state was last updated.
-     */
-    DateTime getLastUpdated(NodeId nodeId);
-
+public interface ClusterService extends MembershipService {
 }
diff --git a/core/api/src/main/java/org/onosproject/cluster/MembershipAdminService.java b/core/api/src/main/java/org/onosproject/cluster/MembershipAdminService.java
new file mode 100644
index 0000000..908a963
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/cluster/MembershipAdminService.java
@@ -0,0 +1,70 @@
+/*
+ * 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.cluster;
+
+import java.util.Set;
+
+import org.onlab.packet.IpAddress;
+
+/**
+ * Service for administering the cluster node membership.
+ */
+public interface MembershipAdminService extends MembershipService {
+
+    /**
+     * Forms cluster configuration based on the specified set of node
+     * information.&nbsp; This method resets and restarts the controller
+     * instance.
+     *
+     * @param nodes    set of nodes that form the cluster
+     */
+    void formCluster(Set<ControllerNode> nodes);
+
+    /**
+     * Forms cluster configuration based on the specified set of node
+     * information.&nbsp; This method resets and restarts the controller
+     * instance.
+     *
+     * @param nodes    set of nodes that form the cluster
+     * @param partitionSize number of nodes to compose a partition
+     */
+    void formCluster(Set<ControllerNode> nodes, int partitionSize);
+
+    /**
+     * Adds a new controller node to the cluster.
+     *
+     * @param nodeId  controller node identifier
+     * @param ip      node IP listen address
+     * @param tcpPort tcp listen port
+     * @return newly added node
+     */
+    ControllerNode addNode(NodeId nodeId, IpAddress ip, int tcpPort);
+
+    /**
+     * Removes the specified node from the cluster node list.
+     *
+     * @param nodeId controller node identifier
+     */
+    void removeNode(NodeId nodeId);
+
+    /**
+     * Marks the current node as fully started or not.
+     *
+     * @param started true indicates all components have been started
+     */
+    void markFullyStarted(boolean started);
+
+}
diff --git a/core/api/src/main/java/org/onosproject/cluster/MembershipService.java b/core/api/src/main/java/org/onosproject/cluster/MembershipService.java
new file mode 100644
index 0000000..7b366f6
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/cluster/MembershipService.java
@@ -0,0 +1,79 @@
+/*
+ * 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.cluster;
+
+import java.util.Set;
+
+import org.joda.time.DateTime;
+import org.onosproject.core.Version;
+import org.onosproject.event.ListenerService;
+
+/**
+ * Service for obtaining information about the individual nodes within
+ * the controller cluster.
+ */
+public interface MembershipService
+    extends ListenerService<ClusterEvent, ClusterEventListener> {
+
+    /**
+     * Returns the local controller node.
+     *
+     * @return local controller node
+     */
+    ControllerNode getLocalNode();
+
+    /**
+     * Returns the set of current cluster members.
+     *
+     * @return set of cluster members
+     */
+    Set<ControllerNode> getNodes();
+
+    /**
+     * Returns the specified controller node.
+     *
+     * @param nodeId controller node identifier
+     * @return controller node
+     */
+    ControllerNode getNode(NodeId nodeId);
+
+    /**
+     * Returns the availability state of the specified controller node. Note
+     * that this does not imply that all the core and application components
+     * have been fully activated; only that the node has joined the cluster.
+     *
+     * @param nodeId controller node identifier
+     * @return availability state
+     */
+    ControllerNode.State getState(NodeId nodeId);
+
+    /**
+     * Returns the version of the given controller node.
+     *
+     * @param nodeId controller node identifier
+     * @return controller version
+     */
+    Version getVersion(NodeId nodeId);
+
+    /**
+     * Returns the system time when the availability state was last updated.
+     *
+     * @param nodeId controller node identifier
+     * @return system time when the availability state was last updated.
+     */
+    DateTime getLastUpdated(NodeId nodeId);
+
+}
diff --git a/core/api/src/main/java/org/onosproject/cluster/PartitionId.java b/core/api/src/main/java/org/onosproject/cluster/PartitionId.java
index f8b65e7..39852de 100644
--- a/core/api/src/main/java/org/onosproject/cluster/PartitionId.java
+++ b/core/api/src/main/java/org/onosproject/cluster/PartitionId.java
@@ -25,6 +25,11 @@
 public class PartitionId extends Identifier<Integer> implements Comparable<PartitionId> {
 
     /**
+     * The {@code PartitionId} for the shared coordination partition.
+     */
+    public static final PartitionId SHARED = PartitionId.from(0);
+
+    /**
      * Creates a partition identifier from an integer.
      *
      * @param id input integer
diff --git a/core/api/src/main/java/org/onosproject/cluster/UnifiedClusterAdminService.java b/core/api/src/main/java/org/onosproject/cluster/UnifiedClusterAdminService.java
new file mode 100644
index 0000000..9fb7407
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/cluster/UnifiedClusterAdminService.java
@@ -0,0 +1,25 @@
+/*
+ * 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.cluster;
+
+import com.google.common.annotations.Beta;
+
+/**
+ * Cluster membership administration service that supports modification of all nodes during an upgrade.
+ */
+@Beta
+public interface UnifiedClusterAdminService extends MembershipAdminService {
+}
diff --git a/core/api/src/main/java/org/onosproject/cluster/UnifiedClusterService.java b/core/api/src/main/java/org/onosproject/cluster/UnifiedClusterService.java
new file mode 100644
index 0000000..f690f3e
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/cluster/UnifiedClusterService.java
@@ -0,0 +1,32 @@
+/*
+ * 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.cluster;
+
+import com.google.common.annotations.Beta;
+
+/**
+ * Unified multi-version cluster membership service.
+ * <p>
+ * During upgrades, the nodes within a cluster may be running multiple versions of the software.
+ * This service has a view of the entire cluster running any version. Users of this service must be careful when
+ * communicating with nodes described by this service as compatibility issues can result from communicating across
+ * versions. For an equivalent service that has an isolated view of the cluster, see {@link ClusterService}.
+ *
+ * @see ClusterService
+ */
+@Beta
+public interface UnifiedClusterService extends MembershipService {
+}
diff --git a/core/api/src/main/java/org/onosproject/store/cluster/messaging/ClusterCommunicationService.java b/core/api/src/main/java/org/onosproject/store/cluster/messaging/ClusterCommunicationService.java
index 4a46885..dfc558d 100644
--- a/core/api/src/main/java/org/onosproject/store/cluster/messaging/ClusterCommunicationService.java
+++ b/core/api/src/main/java/org/onosproject/store/cluster/messaging/ClusterCommunicationService.java
@@ -15,152 +15,15 @@
  */
 package org.onosproject.store.cluster.messaging;
 
-import java.util.Set;
-import java.util.concurrent.CompletableFuture;
-import java.util.concurrent.Executor;
-import java.util.concurrent.ExecutorService;
-import java.util.function.Consumer;
-import java.util.function.Function;
-
-import org.onosproject.cluster.NodeId;
-
 /**
  * Service for assisting communications between controller cluster nodes.
+ * <p>
+ * Communication via this service is isolated to nodes running a single version of the software. During upgrades, when
+ * nodes may be running multiple versions simultaneously, this service prevents nodes running different versions of
+ * the software from communicating with each other, thus avoiding compatibility issues. For an equivalent cross-version
+ * compatible service, see {@link UnifiedClusterCommunicationService}.
+ *
+ * @see UnifiedClusterCommunicationService
  */
-public interface ClusterCommunicationService {
-
-    /**
-     * Adds a new subscriber for the specified message subject.
-     *
-     * @param subject    message subject
-     * @param subscriber message subscriber
-     * @param executor executor to use for running handler.
-     * @deprecated in Cardinal Release
-     */
-    @Deprecated
-    void addSubscriber(MessageSubject subject, ClusterMessageHandler subscriber, ExecutorService executor);
-
-    /**
-     * Broadcasts a message to all controller nodes.
-     *
-     * @param message message to send
-     * @param subject message subject
-     * @param encoder function for encoding message to byte[]
-     * @param <M> message type
-     */
-    <M> void broadcast(M message,
-                       MessageSubject subject,
-                       Function<M, byte[]> encoder);
-
-    /**
-     * Broadcasts a message to all controller nodes including self.
-     *
-     * @param message message to send
-     * @param subject message subject
-     * @param encoder function for encoding message to byte[]
-     * @param <M> message type
-     */
-    <M> void broadcastIncludeSelf(M message,
-                                  MessageSubject subject,
-                                  Function<M, byte[]> encoder);
-
-    /**
-     * Sends a message to the specified controller node.
-     *
-     * @param message message to send
-     * @param subject message subject
-     * @param encoder function for encoding message to byte[]
-     * @param toNodeId destination node identifier
-     * @param <M> message type
-     * @return future that is completed when the message is sent
-     */
-    <M> CompletableFuture<Void> unicast(M message,
-                        MessageSubject subject,
-                        Function<M, byte[]> encoder,
-                        NodeId toNodeId);
-
-    /**
-     * Multicasts a message to a set of controller nodes.
-     *
-     * @param message message to send
-     * @param subject message subject
-     * @param encoder function for encoding message to byte[]
-     * @param nodeIds  recipient node identifiers
-     * @param <M> message type
-     */
-    <M> void multicast(M message,
-                       MessageSubject subject,
-                       Function<M, byte[]> encoder,
-                       Set<NodeId> nodeIds);
-
-    /**
-     * Sends a message and expects a reply.
-     *
-     * @param message message to send
-     * @param subject message subject
-     * @param encoder function for encoding request to byte[]
-     * @param decoder function for decoding response from byte[]
-     * @param toNodeId recipient node identifier
-     * @param <M> request type
-     * @param <R> reply type
-     * @return reply future
-     */
-    <M, R> CompletableFuture<R> sendAndReceive(M message,
-                                               MessageSubject subject,
-                                               Function<M, byte[]> encoder,
-                                               Function<byte[], R> decoder,
-                                               NodeId toNodeId);
-
-    /**
-     * Adds a new subscriber for the specified message subject.
-     *
-     * @param subject message subject
-     * @param decoder decoder for resurrecting incoming message
-     * @param handler handler function that processes the incoming message and produces a reply
-     * @param encoder encoder for serializing reply
-     * @param executor executor to run this handler on
-     * @param <M> incoming message type
-     * @param <R> reply message type
-     */
-    <M, R> void addSubscriber(MessageSubject subject,
-                              Function<byte[], M> decoder,
-                              Function<M, R> handler,
-                              Function<R, byte[]> encoder,
-                              Executor executor);
-
-    /**
-     * Adds a new subscriber for the specified message subject.
-     *
-     * @param subject message subject
-     * @param decoder decoder for resurrecting incoming message
-     * @param handler handler function that processes the incoming message and produces a reply
-     * @param encoder encoder for serializing reply
-     * @param <M> incoming message type
-     * @param <R> reply message type
-     */
-    <M, R> void addSubscriber(MessageSubject subject,
-                              Function<byte[], M> decoder,
-                              Function<M, CompletableFuture<R>> handler,
-                              Function<R, byte[]> encoder);
-
-    /**
-     * Adds a new subscriber for the specified message subject.
-     *
-     * @param subject message subject
-     * @param decoder decoder to resurrecting incoming message
-     * @param handler handler for handling message
-     * @param executor executor to run this handler on
-     * @param <M> incoming message type
-     */
-    <M> void addSubscriber(MessageSubject subject,
-                           Function<byte[], M> decoder,
-                           Consumer<M> handler,
-                           Executor executor);
-
-    /**
-     * Removes a subscriber for the specified message subject.
-     *
-     * @param subject message subject
-     */
-    void removeSubscriber(MessageSubject subject);
+public interface ClusterCommunicationService extends ClusterCommunicator {
 }
diff --git a/core/api/src/main/java/org/onosproject/store/cluster/messaging/ClusterCommunicator.java b/core/api/src/main/java/org/onosproject/store/cluster/messaging/ClusterCommunicator.java
new file mode 100644
index 0000000..7d2480e
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/store/cluster/messaging/ClusterCommunicator.java
@@ -0,0 +1,166 @@
+/*
+ * 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.store.cluster.messaging;
+
+import java.util.Set;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.Executor;
+import java.util.concurrent.ExecutorService;
+import java.util.function.Consumer;
+import java.util.function.Function;
+
+import org.onosproject.cluster.NodeId;
+
+/**
+ * Service for assisting communications between controller cluster nodes.
+ */
+public interface ClusterCommunicator {
+
+    /**
+     * Adds a new subscriber for the specified message subject.
+     *
+     * @param subject    message subject
+     * @param subscriber message subscriber
+     * @param executor executor to use for running handler.
+     * @deprecated in Cardinal Release
+     */
+    @Deprecated
+    void addSubscriber(MessageSubject subject, ClusterMessageHandler subscriber, ExecutorService executor);
+
+    /**
+     * Broadcasts a message to all controller nodes.
+     *
+     * @param message message to send
+     * @param subject message subject
+     * @param encoder function for encoding message to byte[]
+     * @param <M> message type
+     */
+    <M> void broadcast(M message,
+            MessageSubject subject,
+            Function<M, byte[]> encoder);
+
+    /**
+     * Broadcasts a message to all controller nodes including self.
+     *
+     * @param message message to send
+     * @param subject message subject
+     * @param encoder function for encoding message to byte[]
+     * @param <M> message type
+     */
+    <M> void broadcastIncludeSelf(M message,
+            MessageSubject subject,
+            Function<M, byte[]> encoder);
+
+    /**
+     * Sends a message to the specified controller node.
+     *
+     * @param message message to send
+     * @param subject message subject
+     * @param encoder function for encoding message to byte[]
+     * @param toNodeId destination node identifier
+     * @param <M> message type
+     * @return future that is completed when the message is sent
+     */
+    <M> CompletableFuture<Void> unicast(M message,
+            MessageSubject subject,
+            Function<M, byte[]> encoder,
+            NodeId toNodeId);
+
+    /**
+     * Multicasts a message to a set of controller nodes.
+     *
+     * @param message message to send
+     * @param subject message subject
+     * @param encoder function for encoding message to byte[]
+     * @param nodeIds  recipient node identifiers
+     * @param <M> message type
+     */
+    <M> void multicast(M message,
+            MessageSubject subject,
+            Function<M, byte[]> encoder,
+            Set<NodeId> nodeIds);
+
+    /**
+     * Sends a message and expects a reply.
+     *
+     * @param message message to send
+     * @param subject message subject
+     * @param encoder function for encoding request to byte[]
+     * @param decoder function for decoding response from byte[]
+     * @param toNodeId recipient node identifier
+     * @param <M> request type
+     * @param <R> reply type
+     * @return reply future
+     */
+    <M, R> CompletableFuture<R> sendAndReceive(M message,
+            MessageSubject subject,
+            Function<M, byte[]> encoder,
+            Function<byte[], R> decoder,
+            NodeId toNodeId);
+
+    /**
+     * Adds a new subscriber for the specified message subject.
+     *
+     * @param subject message subject
+     * @param decoder decoder for resurrecting incoming message
+     * @param handler handler function that processes the incoming message and produces a reply
+     * @param encoder encoder for serializing reply
+     * @param executor executor to run this handler on
+     * @param <M> incoming message type
+     * @param <R> reply message type
+     */
+    <M, R> void addSubscriber(MessageSubject subject,
+            Function<byte[], M> decoder,
+            Function<M, R> handler,
+            Function<R, byte[]> encoder,
+            Executor executor);
+
+    /**
+     * Adds a new subscriber for the specified message subject.
+     *
+     * @param subject message subject
+     * @param decoder decoder for resurrecting incoming message
+     * @param handler handler function that processes the incoming message and produces a reply
+     * @param encoder encoder for serializing reply
+     * @param <M> incoming message type
+     * @param <R> reply message type
+     */
+    <M, R> void addSubscriber(MessageSubject subject,
+            Function<byte[], M> decoder,
+            Function<M, CompletableFuture<R>> handler,
+            Function<R, byte[]> encoder);
+
+    /**
+     * Adds a new subscriber for the specified message subject.
+     *
+     * @param subject message subject
+     * @param decoder decoder to resurrecting incoming message
+     * @param handler handler for handling message
+     * @param executor executor to run this handler on
+     * @param <M> incoming message type
+     */
+    <M> void addSubscriber(MessageSubject subject,
+            Function<byte[], M> decoder,
+            Consumer<M> handler,
+            Executor executor);
+
+    /**
+     * Removes a subscriber for the specified message subject.
+     *
+     * @param subject message subject
+     */
+    void removeSubscriber(MessageSubject subject);
+}
diff --git a/core/api/src/main/java/org/onosproject/store/cluster/messaging/UnifiedClusterCommunicationService.java b/core/api/src/main/java/org/onosproject/store/cluster/messaging/UnifiedClusterCommunicationService.java
new file mode 100644
index 0000000..042c803
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/store/cluster/messaging/UnifiedClusterCommunicationService.java
@@ -0,0 +1,31 @@
+/*
+ * 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.store.cluster.messaging;
+
+import com.google.common.annotations.Beta;
+
+/**
+ * Service for unified communication across controller nodes running multiple software versions.
+ * <p>
+ * This service supports communicating across nodes running different versions of the software simultaneously. During
+ * upgrades, when nodes may be running a mixture of versions, this service can be used to coordinate across those
+ * versions. But users of this service must be extremely careful to preserve backward/forward compatibility for
+ * messages sent across versions. Encoders and decoders used for messages sent/received on this service should
+ * support evolving schemas.
+ */
+@Beta
+public interface UnifiedClusterCommunicationService extends ClusterCommunicator {
+}
diff --git a/core/api/src/main/java/org/onosproject/store/service/AtomicValue.java b/core/api/src/main/java/org/onosproject/store/service/AtomicValue.java
index a9547c9..adca843 100644
--- a/core/api/src/main/java/org/onosproject/store/service/AtomicValue.java
+++ b/core/api/src/main/java/org/onosproject/store/service/AtomicValue.java
@@ -22,6 +22,11 @@
  */
 public interface AtomicValue<V> extends DistributedPrimitive  {
 
+    @Override
+    default Type primitiveType() {
+        return Type.VALUE;
+    }
+
     /**
      * Atomically sets the value to the given updated value if the current value is equal to the expected value.
      * <p>
diff --git a/core/api/src/main/java/org/onosproject/store/service/CoordinationService.java b/core/api/src/main/java/org/onosproject/store/service/CoordinationService.java
new file mode 100644
index 0000000..8725a06
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/store/service/CoordinationService.java
@@ -0,0 +1,35 @@
+/*
+ * 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.store.service;
+
+import com.google.common.annotations.Beta;
+
+/**
+ * Cross-version storage/coordination service.
+ * <p>
+ * This is a special type of {@link PrimitiveService} that differs semantically from {@link StorageService} in that
+ * it supports cross-version backward/forward compatible storage. During upgrades, when nodes are running different
+ * versions of the software, this service guarantees that cross-version compatibility will be maintained and provides
+ * shared compatible primitives for coordinating across versions. Users must ensure that all objects stored in
+ * primitives created via this service are stored using a serialization format that is backward/forward compatible,
+ * e.g. using {@link org.onlab.util.KryoNamespace.Builder#setCompatible(boolean)}.
+ *
+ * @see org.onlab.util.KryoNamespace.Builder#setCompatible(boolean)
+ * @see StorageService
+ */
+@Beta
+public interface CoordinationService extends PrimitiveService {
+}
diff --git a/core/api/src/main/java/org/onosproject/store/service/PartitionInfo.java b/core/api/src/main/java/org/onosproject/store/service/PartitionInfo.java
index fb903b8..c3c3835 100644
--- a/core/api/src/main/java/org/onosproject/store/service/PartitionInfo.java
+++ b/core/api/src/main/java/org/onosproject/store/service/PartitionInfo.java
@@ -15,15 +15,16 @@
  */
 package org.onosproject.store.service;
 
-import com.google.common.collect.ImmutableList;
-
 import java.util.List;
 
+import com.google.common.collect.ImmutableList;
+import org.onosproject.cluster.PartitionId;
+
 /**
  * Contains information about a database partition.
  */
 public class PartitionInfo {
-    private final String name;
+    private final PartitionId partitionId;
     private final long term;
     private final List<String> members;
     private final String leader;
@@ -31,25 +32,25 @@
     /**
      * Class constructor.
      *
-     * @param name partition name
+     * @param partitionId partition identifier
      * @param term term number
      * @param members partition members
      * @param leader leader name
      */
-    public PartitionInfo(String name, long term, List<String> members, String leader) {
-        this.name = name;
+    public PartitionInfo(PartitionId partitionId, long term, List<String> members, String leader) {
+        this.partitionId = partitionId;
         this.term = term;
         this.members = ImmutableList.copyOf(members);
         this.leader = leader;
     }
 
     /**
-     * Returns the name of the partition.
+     * Returns the partition ID.
      *
-     * @return partition name
+     * @return partition ID
      */
-    public String name() {
-        return name;
+    public PartitionId id() {
+        return partitionId;
     }
 
     /**
diff --git a/core/api/src/main/java/org/onosproject/store/service/PrimitiveService.java b/core/api/src/main/java/org/onosproject/store/service/PrimitiveService.java
new file mode 100644
index 0000000..7be0480
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/store/service/PrimitiveService.java
@@ -0,0 +1,217 @@
+/*
+ * 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.store.service;
+
+/**
+ * Primitive service.
+ * <p>
+ * This service provides builders for various distributed primitives.
+ * <p>
+ * It is expected that services and applications will leverage the primitives indirectly provided by
+ * this service for their distributed state management and coordination.
+ */
+public interface PrimitiveService {
+
+    /**
+     * Creates a new EventuallyConsistentMapBuilder.
+     *
+     * @param <K> key type
+     * @param <V> value type
+     * @return builder for an eventually consistent map
+     */
+    <K, V> EventuallyConsistentMapBuilder<K, V> eventuallyConsistentMapBuilder();
+
+    /**
+     * Creates a new ConsistentMapBuilder.
+     *
+     * @param <K> key type
+     * @param <V> value type
+     * @return builder for a consistent map
+     */
+    <K, V> ConsistentMapBuilder<K, V> consistentMapBuilder();
+
+    /**
+     * Creates a new ConsistentMapBuilder.
+     *
+     * @param <V> value type
+     * @return builder for a document tree
+     */
+    <V> DocumentTreeBuilder<V> documentTreeBuilder();
+
+    /**
+     * Creates a new {@code AsyncConsistentTreeMapBuilder}.
+     *
+     * @param <V> value type
+     * @return builder for a consistent tree map
+     */
+    <V> ConsistentTreeMapBuilder<V> consistentTreeMapBuilder();
+
+    /**
+     * Creates a new {@code AsyncConsistentSetMultimapBuilder}.
+     *
+     * @param <K> key type
+     * @param <V> value type
+     * @return builder for a set based consistent multimap
+     */
+    <K, V> ConsistentMultimapBuilder<K, V> consistentMultimapBuilder();
+
+    /**
+     * Creates a new {@code AtomicCounterMapBuilder}.
+     *
+     * @param <K> key type
+     * @return builder for an atomic counter map
+     */
+    <K> AtomicCounterMapBuilder<K> atomicCounterMapBuilder();
+
+    /**
+     * Creates a new DistributedSetBuilder.
+     *
+     * @param <E> set element type
+     * @return builder for a distributed set
+     */
+    <E> DistributedSetBuilder<E> setBuilder();
+
+    /**
+     * Creates a new AtomicCounterBuilder.
+     *
+     * @return atomic counter builder
+     */
+    AtomicCounterBuilder atomicCounterBuilder();
+
+    /**
+     * Creates a new AtomicIdGeneratorBuilder.
+     *
+     * @return atomic ID generator builder
+     */
+    AtomicIdGeneratorBuilder atomicIdGeneratorBuilder();
+
+    /**
+     * Creates a new AtomicValueBuilder.
+     *
+     * @param <V> atomic value type
+     * @return atomic value builder
+     */
+    <V> AtomicValueBuilder<V> atomicValueBuilder();
+
+    /**
+     * Creates a new LeaderElectorBuilder.
+     *
+     * @return leader elector builder
+     */
+    LeaderElectorBuilder leaderElectorBuilder();
+
+    /**
+     * Creates a new transaction context builder.
+     *
+     * @return a builder for a transaction context.
+     */
+    TransactionContextBuilder transactionContextBuilder();
+
+    /**
+     * Returns an instance of {@code AsyncAtomicCounter} with specified name.
+     * @param name counter name
+     *
+     * @return AsyncAtomicCounter instance
+     */
+    default AsyncAtomicCounter getAsyncAtomicCounter(String name) {
+        return atomicCounterBuilder().withName(name).build();
+    }
+
+    /**
+     * Returns an instance of {@code AsyncAtomicIdGenerator} with specified name.
+     *
+     * @param name ID generator name
+     * @return AsyncAtomicIdGenerator instance
+     */
+    default AsyncAtomicIdGenerator getAsyncAtomicIdGenerator(String name) {
+        return atomicIdGeneratorBuilder().withName(name).build();
+    }
+
+    /**
+     * Returns an instance of {@code AtomicCounter} with specified name.
+     * @param name counter name
+     *
+     * @return AtomicCounter instance
+     */
+    default AtomicCounter getAtomicCounter(String name) {
+        return getAsyncAtomicCounter(name).asAtomicCounter();
+    }
+
+    /**
+     * Returns an instance of {@code AtomicIdGenerator} with specified name.
+     *
+     * @param name ID generator name
+     * @return AtomicIdGenerator instance
+     */
+    default AtomicIdGenerator getAtomicIdGenerator(String name) {
+        return getAsyncAtomicIdGenerator(name).asAtomicIdGenerator();
+    }
+
+    /**
+     * Returns an instance of {@code WorkQueue} with specified name.
+     *
+     * @param <E> work element type
+     * @param name work queue name
+     * @param serializer serializer
+     * @return WorkQueue instance
+     */
+    <E> WorkQueue<E> getWorkQueue(String name, Serializer serializer);
+
+    /**
+     * Returns an instance of {@code AsyncDocumentTree} with specified name.
+     *
+     * @param <V> tree node value type
+     * @param name document tree name
+     * @param serializer serializer
+     * @return AsyncDocumentTree instance
+     */
+    <V> AsyncDocumentTree<V> getDocumentTree(String name, Serializer serializer);
+
+     /** Returns a set backed instance of {@code AsyncConsistentMultimap} with
+     * the specified name.
+     *
+     * @param name the multimap name
+     * @param serializer serializer
+     * @param <K> key type
+     * @param <V> value type
+     * @return set backed {@code AsyncConsistentMultimap} instance
+     */
+    <K, V> AsyncConsistentMultimap<K, V> getAsyncSetMultimap(String name,
+            Serializer serializer);
+
+    /**
+     * Returns an instance of {@code AsyncConsistentTreeMap} with the specified
+     * name.
+     *
+     * @param name the treemap name
+     * @param serializer serializer
+     * @param <V> value type
+     * @return set backed {@code AsyncConsistentTreeMap} instance
+     */
+    <V> AsyncConsistentTreeMap<V> getAsyncTreeMap(String name,
+            Serializer serializer);
+
+    /**
+     * Returns an instance of {@code Topic} with specified name.
+     *
+     * @param <T> topic message type
+     * @param name topic name
+     * @param serializer serializer
+     *
+     * @return Topic instance
+     */
+    <T> Topic<T> getTopic(String name, Serializer serializer);
+}
diff --git a/core/api/src/main/java/org/onosproject/store/service/StorageService.java b/core/api/src/main/java/org/onosproject/store/service/StorageService.java
index d863983..94843fc 100644
--- a/core/api/src/main/java/org/onosproject/store/service/StorageService.java
+++ b/core/api/src/main/java/org/onosproject/store/service/StorageService.java
@@ -23,195 +23,5 @@
  * It is expected that services and applications will leverage the primitives indirectly provided by
  * this service for their distributed state management and coordination.
  */
-public interface StorageService {
-
-    /**
-     * Creates a new EventuallyConsistentMapBuilder.
-     *
-     * @param <K> key type
-     * @param <V> value type
-     * @return builder for an eventually consistent map
-     */
-    <K, V> EventuallyConsistentMapBuilder<K, V> eventuallyConsistentMapBuilder();
-
-    /**
-     * Creates a new ConsistentMapBuilder.
-     *
-     * @param <K> key type
-     * @param <V> value type
-     * @return builder for a consistent map
-     */
-    <K, V> ConsistentMapBuilder<K, V> consistentMapBuilder();
-
-    /**
-     * Creates a new ConsistentMapBuilder.
-     *
-     * @param <V> value type
-     * @return builder for a consistent map
-     */
-    <V> DocumentTreeBuilder<V> documentTreeBuilder();
-
-    /**
-     * Creates a new {@code AsyncConsistentTreeMapBuilder}.
-     *
-     * @param <V> value type
-     * @return builder for a async consistent tree map
-     */
-    <V> ConsistentTreeMapBuilder<V> consistentTreeMapBuilder();
-
-    /**
-     * Creates a new {@code AsyncConsistentSetMultimapBuilder}.
-     *
-     * @param <K> key type
-     * @param <V> value type
-     * @return builder for a set based async consistent multimap
-     */
-    <K, V> ConsistentMultimapBuilder<K, V> consistentMultimapBuilder();
-
-    /**
-     * Creates a new {@code AtomicCounterMapBuilder}.
-     *
-     * @param <K> key type
-     * @return builder for an atomic counter map
-     */
-    <K> AtomicCounterMapBuilder<K> atomicCounterMapBuilder();
-
-    /**
-     * Creates a new DistributedSetBuilder.
-     *
-     * @param <E> set element type
-     * @return builder for an distributed set
-     */
-    <E> DistributedSetBuilder<E> setBuilder();
-
-    /**
-     * Creates a new AtomicCounterBuilder.
-     *
-     * @return atomic counter builder
-     */
-    AtomicCounterBuilder atomicCounterBuilder();
-
-    /**
-     * Creates a new AtomicIdGeneratorBuilder.
-     *
-     * @return atomic ID generator builder
-     */
-    AtomicIdGeneratorBuilder atomicIdGeneratorBuilder();
-
-    /**
-     * Creates a new AtomicValueBuilder.
-     *
-     * @param <V> atomic value type
-     * @return atomic value builder
-     */
-    <V> AtomicValueBuilder<V> atomicValueBuilder();
-
-    /**
-     * Creates a new LeaderElectorBuilder.
-     *
-     * @return leader elector builder
-     */
-    LeaderElectorBuilder leaderElectorBuilder();
-
-    /**
-     * Creates a new transaction context builder.
-     *
-     * @return a builder for a transaction context.
-     */
-    TransactionContextBuilder transactionContextBuilder();
-
-    /**
-     * Returns an instance of {@code AsyncAtomicCounter} with specified name.
-     * @param name counter name
-     *
-     * @return AsyncAtomicCounter instance
-     */
-    default AsyncAtomicCounter getAsyncAtomicCounter(String name) {
-        return atomicCounterBuilder().withName(name).build();
-    }
-
-    /**
-     * Returns an instance of {@code AsyncAtomicIdGenerator} with specified name.
-     *
-     * @param name ID generator name
-     * @return AsyncAtomicIdGenerator instance
-     */
-    default AsyncAtomicIdGenerator getAsyncAtomicIdGenerator(String name) {
-        return atomicIdGeneratorBuilder().withName(name).build();
-    }
-
-    /**
-     * Returns an instance of {@code AtomicCounter} with specified name.
-     * @param name counter name
-     *
-     * @return AtomicCounter instance
-     */
-    default AtomicCounter getAtomicCounter(String name) {
-        return getAsyncAtomicCounter(name).asAtomicCounter();
-    }
-
-    /**
-     * Returns an instance of {@code AtomicIdGenerator} with specified name.
-     *
-     * @param name ID generator name
-     * @return AtomicIdGenerator instance
-     */
-    default AtomicIdGenerator getAtomicIdGenerator(String name) {
-        return getAsyncAtomicIdGenerator(name).asAtomicIdGenerator();
-    }
-
-    /**
-     * Returns an instance of {@code WorkQueue} with specified name.
-     *
-     * @param <E> work element type
-     * @param name work queue name
-     * @param serializer serializer
-     * @return WorkQueue instance
-     */
-    <E> WorkQueue<E> getWorkQueue(String name, Serializer serializer);
-
-    /**
-     * Returns an instance of {@code AsyncDocumentTree} with specified name.
-     *
-     * @param <V> tree node value type
-     * @param name document tree name
-     * @param serializer serializer
-     * @return AsyncDocumentTree instance
-     */
-    <V> AsyncDocumentTree<V> getDocumentTree(String name, Serializer serializer);
-
-     /** Returns a set backed instance of {@code AsyncConsistentMultimap} with
-     * the specified name.
-     *
-     * @param name the multimap name
-     * @param serializer serializer
-     * @param <K> key type
-     * @param <V> value type
-     * @return set backed {@code AsyncConsistentMultimap} instance
-     */
-    <K, V> AsyncConsistentMultimap<K, V> getAsyncSetMultimap(String name,
-                                                             Serializer serializer);
-
-    /**
-     * Returns an instance of {@code AsyncConsistentTreeMap} with the specified
-     * name.
-     *
-     * @param name the treemap name
-     * @param serializer serializer
-     * @param <V> value type
-     * @return set backed {@code AsyncConsistentTreeMap} instance
-     */
-    <V> AsyncConsistentTreeMap<V> getAsyncTreeMap(String name,
-                                                  Serializer serializer);
-
-    /**
-     * Returns an instance of {@code Topic} with specified name.
-     *
-     * @param <T> topic message type
-     * @param name topic name
-     * @param serializer serializer
-     *
-     * @return Topic instance
-     */
-    <T> Topic<T> getTopic(String name, Serializer serializer);
+public interface StorageService extends PrimitiveService {
 }
diff --git a/core/api/src/main/java/org/onosproject/upgrade/Upgrade.java b/core/api/src/main/java/org/onosproject/upgrade/Upgrade.java
new file mode 100644
index 0000000..79fa7ba
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/upgrade/Upgrade.java
@@ -0,0 +1,165 @@
+/*
+ * 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;
+
+import com.google.common.annotations.Beta;
+import org.onosproject.core.Version;
+
+import static com.google.common.base.MoreObjects.toStringHelper;
+
+/**
+ * Represents the state of an upgrade.
+ * <p>
+ * An upgrade consists of a {@link #source() source} and {@link #target() target} version and an upgrade
+ * {@link #status()}.
+ */
+@Beta
+public class Upgrade {
+
+    /**
+     * Represents the phase of the upgrade protocol.
+     */
+    @Beta
+    public enum Status {
+
+        /**
+         * Represents state in which no upgrade has been initialized.
+         */
+        INACTIVE(false, false),
+
+        /**
+         * Indicates that an upgrade is being initialized.
+         */
+        INITIALIZING(true, false),
+
+        /**
+         * Indicates that an upgrade has been initialized.
+         */
+        INITIALIZED(true, false),
+
+        /**
+         * Indicates that an upgrade is in progress.
+         */
+        UPGRADING(true, true),
+
+        /**
+         * Indicates that an upgrade is complete.
+         */
+        UPGRADED(true, true),
+
+        /**d
+         * Indicates that an upgrade is being committed.
+         */
+        COMMITTING(true, true),
+
+        /**
+         * Indicates that an upgrade has been committed.
+         */
+        COMMITTED(false, true),
+
+        /**
+         * Indicates that an upgrade is being rolled back.
+         */
+        ROLLING_BACK(true, false),
+
+        /**
+         * Indicates that an upgrade has been rolled back.
+         */
+        ROLLED_BACK(true, false),
+
+        /**
+         * Indicates that an upgrade is being reset.
+         */
+        RESETTING(true, false),
+
+        /**
+         * Indicates that an upgrade has been reset.
+         */
+        RESET(false, false);
+
+        private final boolean active;
+        private final boolean upgraded;
+
+        Status(boolean active, boolean upgraded) {
+            this.active = active;
+            this.upgraded = upgraded;
+        }
+
+        /**
+         * Returns whether the upgrade status is active.
+         *
+         * @return whether the upgrade status is active
+         */
+        public boolean active() {
+            return active;
+        }
+
+        /**
+         * Returns whether the upgraded version is active.
+         *
+         * @return whether the upgraded version is active
+         */
+        public boolean upgraded() {
+            return upgraded;
+        }
+    }
+
+    private final Version source;
+    private final Version target;
+    private final Status status;
+
+    public Upgrade(Version source, Version target, Status status) {
+        this.source = source;
+        this.target = target;
+        this.status = status;
+    }
+
+    /**
+     * Returns the source version.
+     *
+     * @return the source version
+     */
+    public Version source() {
+        return source;
+    }
+
+    /**
+     * Returns the target version.
+     *
+     * @return the target version
+     */
+    public Version target() {
+        return target;
+    }
+
+    /**
+     * Returns the upgrade status.
+     *
+     * @return the upgrade status
+     */
+    public Status status() {
+        return status;
+    }
+
+    @Override
+    public String toString() {
+        return toStringHelper(this)
+                .add("source", source)
+                .add("target", target)
+                .add("status", status)
+                .toString();
+    }
+}
diff --git a/core/api/src/main/java/org/onosproject/upgrade/UpgradeAdminService.java b/core/api/src/main/java/org/onosproject/upgrade/UpgradeAdminService.java
new file mode 100644
index 0000000..38c1bb1
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/upgrade/UpgradeAdminService.java
@@ -0,0 +1,84 @@
+/*
+ * 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;
+
+import com.google.common.annotations.Beta;
+
+/**
+ * Abstraction for executing the stages of the upgrade process.
+ * <p>
+ * Upgrades are performed in three phases:
+ * <ul>
+ *     <li>{@code initialize} - Initializes an upgrade</li>
+ *     <li>{@code upgrade} - Performs an upgrade, transferring device mastership from the current version to the
+ *     upgraded version</li>
+ *     <li>{@code commit} or {@code rollback} - Completes or rolls back an upgrade, transferring mastership back
+ *     to nodes running the previous version</li>
+ * </ul>
+ */
+@Beta
+public interface UpgradeAdminService {
+
+    /**
+     * Initializes an upgrade.
+     * <p>
+     * This method must be called to initialize an upgrade and prior to physically upgrading any nodes.
+     *
+     * @throws IllegalStateException if an upgrade is already in progress
+     */
+    void initialize();
+
+    /**
+     * Performs an upgrade, transferring device mastership to upgraded nodes.
+     * <p>
+     * This method transfers mastership from the current version of the software to the upgraded version. Thus,
+     * a subset of the nodes in the cluster must have been physically upgraded and restarted prior to executing this
+     * phase of the upgrade protocol.
+     *
+     * @throws IllegalStateException if no upgrade has been initialized
+     */
+    void upgrade();
+
+    /**
+     * Commits an upgrade.
+     * <p>
+     * Completes the upgrade process, committing the new cluster version.
+     *
+     * @throws IllegalStateException if no upgrade is in progress or not all nodes have been upgraded
+     */
+    void commit();
+
+    /**
+     * Rolls back an upgrade.
+     * <p>
+     * When an upgrade is rolled back, mastership is transferred from upgraded nodes back to nodes running the
+     * version of the software prior to the upgrade.
+     *
+     * @throws IllegalStateException if no upgrade is in progress
+     */
+    void rollback();
+
+    /**
+     * Resets an upgrade.
+     * <p>
+     * When an upgrade is rolled back, once nodes have been restored to the previos version the upgrade must be reset
+     * to restore the upgrade state to {@link Upgrade.Status#INACTIVE}.
+     *
+     * @throws IllegalStateException if nodes have not been restored to the previous state
+     */
+    void reset();
+
+}
diff --git a/core/api/src/main/java/org/onosproject/upgrade/UpgradeEvent.java b/core/api/src/main/java/org/onosproject/upgrade/UpgradeEvent.java
new file mode 100644
index 0000000..43cf523
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/upgrade/UpgradeEvent.java
@@ -0,0 +1,112 @@
+/*
+ * 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;
+
+import java.util.Objects;
+
+import com.google.common.annotations.Beta;
+import com.google.common.base.MoreObjects;
+import org.onosproject.event.AbstractEvent;
+
+/**
+ * Upgrade event.
+ */
+@Beta
+public class UpgradeEvent extends AbstractEvent<UpgradeEvent.Type, Upgrade> {
+
+    /**
+     * Type of upgrade-related events.
+     */
+    @Beta
+    public enum Type {
+
+        /**
+         * Indicates that a new upgrade was initialized.
+         */
+        INITIALIZED,
+
+        /**
+         * Indicates that mastership was reassigned to the upgraded cluster.
+         */
+        UPGRADED,
+
+        /**
+         * Indicates that an upgrade was committed.
+         */
+        COMMITTED,
+
+        /**
+         * Indicates that an upgrade was rolled back.
+         */
+        ROLLED_BACK,
+
+        /**
+         * Indicates that an upgrade was reset.
+         */
+        RESET,
+    }
+
+    /**
+     * Creates an event of a given type and for the specified state and the
+     * current time.
+     *
+     * @param type  upgrade event type
+     * @param state upgrade state
+     */
+    public UpgradeEvent(UpgradeEvent.Type type, Upgrade state) {
+        super(type, state);
+    }
+
+    /**
+     * Creates an event of a given type and for the specified state and time.
+     *
+     * @param type  upgrade event type
+     * @param state upgrade state
+     * @param time  occurrence time
+     */
+    public UpgradeEvent(UpgradeEvent.Type type, Upgrade state, long time) {
+        super(type, state, time);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(type(), subject(), time());
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+        if (obj instanceof UpgradeEvent) {
+            final UpgradeEvent other = (UpgradeEvent) obj;
+            return Objects.equals(this.type(), other.type()) &&
+                    Objects.equals(this.subject(), other.subject()) &&
+                    Objects.equals(this.time(), other.time());
+        }
+        return false;
+    }
+
+    @Override
+    public String toString() {
+        return MoreObjects.toStringHelper(this.getClass())
+                .add("type", type())
+                .add("subject", subject())
+                .add("time", time())
+                .toString();
+    }
+
+}
diff --git a/core/api/src/main/java/org/onosproject/upgrade/UpgradeEventListener.java b/core/api/src/main/java/org/onosproject/upgrade/UpgradeEventListener.java
new file mode 100644
index 0000000..876d35a
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/upgrade/UpgradeEventListener.java
@@ -0,0 +1,26 @@
+/*
+ * 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;
+
+import com.google.common.annotations.Beta;
+import org.onosproject.event.EventListener;
+
+/**
+ * Upgrade event listener.
+ */
+@Beta
+public interface UpgradeEventListener extends EventListener<UpgradeEvent> {
+}
diff --git a/core/api/src/main/java/org/onosproject/upgrade/UpgradeService.java b/core/api/src/main/java/org/onosproject/upgrade/UpgradeService.java
new file mode 100644
index 0000000..ba5889c
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/upgrade/UpgradeService.java
@@ -0,0 +1,74 @@
+/*
+ * 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;
+
+import com.google.common.annotations.Beta;
+import org.onosproject.core.Version;
+import org.onosproject.event.ListenerService;
+
+/**
+ * Upgrade service.
+ */
+@Beta
+public interface UpgradeService
+        extends ListenerService<UpgradeEvent, UpgradeEventListener> {
+
+    /**
+     * Returns whether an upgrade is in progress.
+     * <p>
+     * An upgrade is in progress if the upgrade {@link Upgrade.Status} is active, e.g.
+     * {@link Upgrade.Status#INITIALIZED}, {@link Upgrade.Status#UPGRADED}, etc.
+     *
+     * @return indicates whether an upgrade is in progress
+     */
+    boolean isUpgrading();
+
+    /**
+     * Returns the current upgrade state.
+     *
+     * @return the current upgrade state
+     */
+    Upgrade getState();
+
+    /**
+     * Returns the currently active software version.
+     * <p>
+     * The returned version is representative of the version currently in control of the network. When the upgrade
+     * transitions to the {@link Upgrade.Status#UPGRADING} state, control over the network is transferred from
+     * {@link Upgrade#source()} nodes to {@link Upgrade#target()} nodes, and the version returned by this method
+     * represents that change.
+     *
+     * @return the software version
+     */
+    Version getVersion();
+
+    /**
+     * Returns whether the local node is active.
+     * <p>
+     * The local node will be active if its {@link Version} matches the version returned by {@link #getVersion()}.
+     *
+     * @return indicates whether the local node is active according to its version
+     */
+    boolean isLocalActive();
+
+    /**
+     * Returns whether the local node is an upgraded node.
+     *
+     * @return {@code true} if the local node's version matches {@link Upgrade#target()}
+     */
+    boolean isLocalUpgraded();
+
+}
diff --git a/core/api/src/main/java/org/onosproject/upgrade/package-info.java b/core/api/src/main/java/org/onosproject/upgrade/package-info.java
new file mode 100644
index 0000000..5f19a54
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/upgrade/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.
+ */
+
+/**
+ * Abstractions for managing software upgrades.
+ */
+package org.onosproject.upgrade;