diff --git a/core/net/src/main/java/org/onosproject/net/group/impl/GroupManager.java b/core/net/src/main/java/org/onosproject/net/group/impl/GroupManager.java
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+++ b/core/net/src/main/java/org/onosproject/net/group/impl/GroupManager.java
@@ -0,0 +1,366 @@
+/*
+ * Copyright 2015 Open Networking Laboratory
+ *
+ * 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.net.group.impl;
+
+import static org.slf4j.LoggerFactory.getLogger;
+
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.Set;
+
+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.core.ApplicationId;
+import org.onosproject.event.AbstractListenerRegistry;
+import org.onosproject.event.EventDeliveryService;
+import org.onosproject.net.DeviceId;
+import org.onosproject.net.group.Group;
+import org.onosproject.net.group.GroupBuckets;
+import org.onosproject.net.group.GroupDescription;
+import org.onosproject.net.group.GroupEvent;
+import org.onosproject.net.group.GroupKey;
+import org.onosproject.net.group.GroupListener;
+import org.onosproject.net.group.GroupOperation;
+import org.onosproject.net.group.GroupOperations;
+import org.onosproject.net.group.GroupProvider;
+import org.onosproject.net.group.GroupProviderRegistry;
+import org.onosproject.net.group.GroupProviderService;
+import org.onosproject.net.group.GroupService;
+import org.onosproject.net.group.GroupStore;
+import org.onosproject.net.group.GroupStore.UpdateType;
+import org.onosproject.net.group.GroupStoreDelegate;
+import org.onosproject.net.provider.AbstractProviderRegistry;
+import org.onosproject.net.provider.AbstractProviderService;
+import org.slf4j.Logger;
+
+import com.google.common.collect.Sets;
+
+/**
+ * Provides implementation of the group service APIs.
+ */
+@Component(immediate = true)
+@Service
+public class GroupManager
+        extends AbstractProviderRegistry<GroupProvider, GroupProviderService>
+        implements GroupService, GroupProviderRegistry {
+
+    private final Logger log = getLogger(getClass());
+
+    private final AbstractListenerRegistry<GroupEvent, GroupListener>
+                listenerRegistry = new AbstractListenerRegistry<>();
+    private final GroupStoreDelegate delegate = new InternalGroupStoreDelegate();
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected GroupStore store;
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected EventDeliveryService eventDispatcher;
+
+    @Activate
+    public void activate() {
+        store.setDelegate(delegate);
+        eventDispatcher.addSink(GroupEvent.class, listenerRegistry);
+        log.info("Started");
+    }
+
+    @Deactivate
+    public void deactivate() {
+        store.unsetDelegate(delegate);
+        eventDispatcher.removeSink(GroupEvent.class);
+        log.info("Stopped");
+    }
+
+    /**
+     * Create a group in the specified device with the provided parameters.
+     *
+     * @param groupDesc group creation parameters
+     *
+     */
+    @Override
+    public void addGroup(GroupDescription groupDesc) {
+        store.storeGroupDescription(groupDesc);
+    }
+
+    /**
+     * Return a group object associated to an application cookie.
+     *
+     * NOTE1: The presence of group object in the system does not
+     * guarantee that the "group" is actually created in device.
+     * GROUP_ADDED notification would confirm the creation of
+     * this group in data plane.
+     *
+     * @param deviceId device identifier
+     * @param appCookie application cookie to be used for lookup
+     * @return group associated with the application cookie or
+     *               NULL if Group is not found for the provided cookie
+     */
+    @Override
+    public Group getGroup(DeviceId deviceId, GroupKey appCookie) {
+        return store.getGroup(deviceId, appCookie);
+    }
+
+    /**
+     * Append buckets to existing group. The caller can optionally
+     * associate a new cookie during this updation. GROUP_UPDATED or
+     * GROUP_UPDATE_FAILED notifications would be provided along with
+     * cookie depending on the result of the operation on the device.
+     *
+     * @param deviceId device identifier
+     * @param oldCookie cookie to be used to retrieve the existing group
+     * @param buckets immutable list of group bucket to be added
+     * @param newCookie immutable cookie to be used post update operation
+     * @param appId Application Id
+     */
+    @Override
+    public void addBucketsToGroup(DeviceId deviceId,
+                           GroupKey oldCookie,
+                           GroupBuckets buckets,
+                           GroupKey newCookie,
+                           ApplicationId appId) {
+        store.updateGroupDescription(deviceId,
+                                     oldCookie,
+                                     UpdateType.ADD,
+                                     buckets,
+                                     newCookie);
+    }
+
+    /**
+     * Remove buckets from existing group. The caller can optionally
+     * associate a new cookie during this updation. GROUP_UPDATED or
+     * GROUP_UPDATE_FAILED notifications would be provided along with
+     * cookie depending on the result of the operation on the device.
+     *
+     * @param deviceId device identifier
+     * @param oldCookie cookie to be used to retrieve the existing group
+     * @param buckets immutable list of group bucket to be removed
+     * @param newCookie immutable cookie to be used post update operation
+     * @param appId Application Id
+     */
+    @Override
+    public void removeBucketsFromGroup(DeviceId deviceId,
+                                GroupKey oldCookie,
+                                GroupBuckets buckets,
+                                GroupKey newCookie,
+                                ApplicationId appId) {
+        store.updateGroupDescription(deviceId,
+                                     oldCookie,
+                                     UpdateType.REMOVE,
+                                     buckets,
+                                     newCookie);
+    }
+
+    /**
+     * Delete a group associated to an application cookie.
+     * GROUP_DELETED or GROUP_DELETE_FAILED notifications would be
+     * provided along with cookie depending on the result of the
+     * operation on the device.
+     *
+     * @param deviceId device identifier
+     * @param appCookie application cookie to be used for lookup
+     * @param appId Application Id
+     */
+    @Override
+    public void removeGroup(DeviceId deviceId,
+                            GroupKey appCookie,
+                            ApplicationId appId) {
+        store.deleteGroupDescription(deviceId, appCookie);
+    }
+
+    /**
+     * Retrieve all groups created by an application in the specified device
+     * as seen by current controller instance.
+     *
+     * @param deviceId device identifier
+     * @param appId application id
+     * @return collection of immutable group objects created by the application
+     */
+    @Override
+    public Iterable<Group> getGroups(DeviceId deviceId,
+                                     ApplicationId appId) {
+        return store.getGroups(deviceId);
+    }
+
+    /**
+     * Adds the specified group listener.
+     *
+     * @param listener group listener
+     */
+    @Override
+    public void addListener(GroupListener listener) {
+        listenerRegistry.addListener(listener);
+    }
+
+    /**
+     * Removes the specified group listener.
+     *
+     * @param listener group listener
+     */
+    @Override
+    public void removeListener(GroupListener listener) {
+        listenerRegistry.removeListener(listener);
+    }
+
+    @Override
+    protected GroupProviderService createProviderService(GroupProvider provider) {
+        return new InternalGroupProviderService(provider);
+    }
+
+    private class InternalGroupStoreDelegate implements GroupStoreDelegate {
+        @Override
+        public void notify(GroupEvent event) {
+            final Group group = event.subject();
+            GroupProvider groupProvider =
+                    getProvider(group.deviceId());
+            GroupOperations groupOps = null;
+            switch (event.type()) {
+            case GROUP_ADD_REQUESTED:
+                GroupOperation groupAddOp = GroupOperation.
+                        createAddGroupOperation(group.id(),
+                                                group.type(),
+                                                group.buckets());
+                groupOps = new GroupOperations(
+                                          Arrays.asList(groupAddOp));
+                groupProvider.performGroupOperation(group.deviceId(), groupOps);
+                break;
+
+            case GROUP_UPDATE_REQUESTED:
+                GroupOperation groupModifyOp = GroupOperation.
+                        createModifyGroupOperation(group.id(),
+                                                group.type(),
+                                                group.buckets());
+                groupOps = new GroupOperations(
+                                   Arrays.asList(groupModifyOp));
+                groupProvider.performGroupOperation(group.deviceId(), groupOps);
+                break;
+
+            case GROUP_REMOVE_REQUESTED:
+                GroupOperation groupDeleteOp = GroupOperation.
+                        createDeleteGroupOperation(group.id(),
+                                                group.type());
+                groupOps = new GroupOperations(
+                                   Arrays.asList(groupDeleteOp));
+                groupProvider.performGroupOperation(group.deviceId(), groupOps);
+                break;
+
+            case GROUP_ADDED:
+            case GROUP_UPDATED:
+            case GROUP_REMOVED:
+                eventDispatcher.post(event);
+                break;
+
+            default:
+                break;
+            }
+        }
+    }
+
+    private class InternalGroupProviderService
+            extends AbstractProviderService<GroupProvider>
+            implements GroupProviderService {
+
+        protected InternalGroupProviderService(GroupProvider provider) {
+            super(provider);
+        }
+
+        @Override
+        public void groupOperationFailed(GroupOperation operation) {
+            // TODO Auto-generated method stub
+
+        }
+
+        private void groupMissing(Group group) {
+            checkValidity();
+            GroupProvider gp = getProvider(group.deviceId());
+            switch (group.state()) {
+                case PENDING_DELETE:
+                    store.removeGroupEntry(group);
+                    break;
+                case ADDED:
+                case PENDING_ADD:
+                    GroupOperation groupAddOp = GroupOperation.
+                                    createAddGroupOperation(group.id(),
+                                                            group.type(),
+                                                            group.buckets());
+                    GroupOperations groupOps = new GroupOperations(
+                                              Arrays.asList(groupAddOp));
+                    gp.performGroupOperation(group.deviceId(), groupOps);
+                    break;
+                default:
+                    log.debug("Group {} has not been installed.", group);
+                    break;
+            }
+        }
+
+
+        private void extraneousGroup(Group group) {
+            log.debug("Group {} is on switch but not in store.", group);
+            checkValidity();
+            store.addOrUpdateExtraneousGroupEntry(group);
+        }
+
+        private void groupAdded(Group group) {
+            checkValidity();
+
+            log.trace("Group {}", group);
+            store.addOrUpdateGroupEntry(group);
+        }
+
+        @Override
+        public void pushGroupMetrics(DeviceId deviceId,
+                                     Collection<Group> groupEntries) {
+            boolean deviceInitialAuditStatus =
+                    store.deviceInitialAuditStatus(deviceId);
+            Set<Group> southboundGroupEntries =
+                    Sets.newHashSet(groupEntries);
+            Set<Group> storedGroupEntries =
+                    Sets.newHashSet(store.getGroups(deviceId));
+            Set<Group> extraneousStoredEntries =
+                    Sets.newHashSet(store.getExtraneousGroups(deviceId));
+
+            for (Iterator<Group> it = southboundGroupEntries.iterator(); it.hasNext();) {
+                Group group = it.next();
+                if (storedGroupEntries.remove(group)) {
+                    // we both have the group, let's update some info then.
+                    groupAdded(group);
+                    it.remove();
+                }
+            }
+            for (Group group : southboundGroupEntries) {
+                // there are groups in the switch that aren't in the store
+                extraneousStoredEntries.remove(group);
+                extraneousGroup(group);
+            }
+            for (Group group : storedGroupEntries) {
+                // there are groups in the store that aren't in the switch
+                groupMissing(group);
+            }
+            for (Group group : extraneousStoredEntries) {
+                // there are groups in the extraneous store that
+                // aren't in the switch
+                store.removeExtraneousGroupEntry(group);
+            }
+
+            if (!deviceInitialAuditStatus) {
+                store.deviceInitialAuditCompleted(deviceId);
+            }
+        }
+    }
+}