diff --git a/core/api/src/main/java/org/onosproject/core/DefaultGroupId.java b/core/api/src/main/java/org/onosproject/core/DefaultGroupId.java
index 11ca73c..58ae9a9 100644
--- a/core/api/src/main/java/org/onosproject/core/DefaultGroupId.java
+++ b/core/api/src/main/java/org/onosproject/core/DefaultGroupId.java
@@ -37,7 +37,7 @@
 
     @Override
     public int id() {
-        return 0;
+        return this.id;
     }
 
     @Override
diff --git a/core/api/src/main/java/org/onosproject/net/group/DefaultGroup.java b/core/api/src/main/java/org/onosproject/net/group/DefaultGroup.java
index 0e4cac1..eba2c6c 100644
--- a/core/api/src/main/java/org/onosproject/net/group/DefaultGroup.java
+++ b/core/api/src/main/java/org/onosproject/net/group/DefaultGroup.java
@@ -17,7 +17,10 @@
 
 import static org.slf4j.LoggerFactory.getLogger;
 
+import java.util.Objects;
+
 import org.onosproject.core.GroupId;
+import org.onosproject.net.DeviceId;
 import org.slf4j.Logger;
 
 /**
@@ -32,6 +35,7 @@
     private long life;
     private long packets;
     private long bytes;
+    private long referenceCount;
     private GroupId id;
 
     /**
@@ -47,6 +51,29 @@
         this.life = 0;
         this.packets = 0;
         this.bytes = 0;
+        this.referenceCount = 0;
+    }
+
+    /**
+     * Default group object constructor with the available information
+     * from data plane.
+     *
+     * @param id group identifier
+     * @param deviceId device identifier
+     * @param type type of the group
+     * @param buckets immutable list of group bucket
+     */
+    public DefaultGroup(GroupId id,
+                        DeviceId deviceId,
+                        GroupDescription.Type type,
+                        GroupBuckets buckets) {
+        super(deviceId, type, buckets);
+        this.id = id;
+        this.state = GroupState.PENDING_ADD;
+        this.life = 0;
+        this.packets = 0;
+        this.bytes = 0;
+        this.referenceCount = 0;
     }
 
     /**
@@ -139,4 +166,43 @@
         this.bytes = bytes;
     }
 
+    @Override
+    public void setReferenceCount(long referenceCount) {
+        this.referenceCount = referenceCount;
+    }
+
+    @Override
+    public long referenceCount() {
+        return referenceCount;
+    }
+
+    /*
+     * The deviceId, type and buckets are used for hash.
+     *
+     * (non-Javadoc)
+     * @see java.lang.Object#equals(java.lang.Object)
+     */
+    @Override
+    public int hashCode() {
+        return super.hashCode() + Objects.hash(id);
+    }
+
+    /*
+     * The deviceId, groupId, type and buckets should be same.
+     *
+     * (non-Javadoc)
+     * @see java.lang.Object#equals(java.lang.Object)
+     */
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+       if (obj instanceof DefaultGroup) {
+            DefaultGroup that = (DefaultGroup) obj;
+            return super.equals(obj) &&
+                    Objects.equals(id, that.id);
+        }
+        return false;
+    }
 }
diff --git a/core/api/src/main/java/org/onosproject/net/group/DefaultGroupBucket.java b/core/api/src/main/java/org/onosproject/net/group/DefaultGroupBucket.java
index 3fab387..931cc71 100644
--- a/core/api/src/main/java/org/onosproject/net/group/DefaultGroupBucket.java
+++ b/core/api/src/main/java/org/onosproject/net/group/DefaultGroupBucket.java
@@ -18,6 +18,8 @@
 import static com.google.common.base.Preconditions.checkArgument;
 import static com.google.common.base.Preconditions.checkNotNull;
 
+import java.util.Objects;
+
 import org.onosproject.core.GroupId;
 import org.onosproject.net.PortNumber;
 import org.onosproject.net.flow.TrafficTreatment;
@@ -178,4 +180,36 @@
     public GroupId watchGroup() {
         return watchGroup;
     }
+
+    /*
+     * The type and treatment can change on a given bucket
+     *
+     * (non-Javadoc)
+     * @see java.lang.Object#equals(java.lang.Object)
+     */
+    @Override
+    public int hashCode() {
+        return Objects.hash(type, treatment);
+    }
+
+    /*
+     * The priority and statistics can change on a given treatment and selector
+     *
+     * (non-Javadoc)
+     * @see java.lang.Object#equals(java.lang.Object)
+     */
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+        if (obj instanceof DefaultGroupBucket) {
+            DefaultGroupBucket that = (DefaultGroupBucket) obj;
+            return Objects.equals(type, that.type) &&
+                   this.treatment.instructions().containsAll(that.treatment.instructions()) &&
+                   that.treatment.instructions().containsAll(this.treatment.instructions());
+        }
+        return false;
+    }
+
 }
diff --git a/core/api/src/main/java/org/onosproject/net/group/DefaultGroupDescription.java b/core/api/src/main/java/org/onosproject/net/group/DefaultGroupDescription.java
index 25af506..8d374c1 100644
--- a/core/api/src/main/java/org/onosproject/net/group/DefaultGroupDescription.java
+++ b/core/api/src/main/java/org/onosproject/net/group/DefaultGroupDescription.java
@@ -17,6 +17,8 @@
 
 import static com.google.common.base.Preconditions.checkNotNull;
 
+import java.util.Objects;
+
 import org.onosproject.core.ApplicationId;
 import org.onosproject.net.DeviceId;
 
@@ -49,8 +51,8 @@
         this.type = checkNotNull(type);
         this.deviceId = checkNotNull(deviceId);
         this.buckets = checkNotNull(buckets);
-        this.appCookie = checkNotNull(appCookie);
-        this.appId = checkNotNull(appId);
+        this.appCookie = appCookie;
+        this.appId = appId;
     }
 
     /**
@@ -61,11 +63,27 @@
      *
      */
     public DefaultGroupDescription(GroupDescription groupDesc) {
-        this.type = checkNotNull(groupDesc.type());
-        this.deviceId = checkNotNull(groupDesc.deviceId());
-        this.buckets = checkNotNull(groupDesc.buckets());
-        this.appCookie = checkNotNull(groupDesc.appCookie());
-        this.appId = checkNotNull(groupDesc.appId());
+        this.type = groupDesc.type();
+        this.deviceId = groupDesc.deviceId();
+        this.buckets = groupDesc.buckets();
+        this.appCookie = groupDesc.appCookie();
+        this.appId = groupDesc.appId();
+    }
+
+    /**
+     * Constructor to be used by group subsystem internal components.
+     * Creates group description object from the information retrieved
+     * from data plane.
+     *
+     * @param deviceId device identifier
+     * @param type type of the group
+     * @param buckets immutable list of group bucket
+     *
+     */
+    public DefaultGroupDescription(DeviceId deviceId,
+                                   GroupDescription.Type type,
+                                   GroupBuckets buckets) {
+        this(deviceId, type, buckets, null, null);
     }
 
     /**
@@ -118,4 +136,36 @@
         return this.buckets;
     }
 
+    @Override
+    /*
+     * The deviceId, type and buckets are used for hash.
+     *
+     * (non-Javadoc)
+     * @see java.lang.Object#equals(java.lang.Object)
+     */
+    public int hashCode() {
+        return Objects.hash(deviceId, type, buckets);
+    }
+
+    @Override
+    /*
+     * The deviceId, type and buckets should be same.
+     *
+     * (non-Javadoc)
+     * @see java.lang.Object#equals(java.lang.Object)
+     */
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+       if (obj instanceof DefaultGroupDescription) {
+            DefaultGroupDescription that = (DefaultGroupDescription) obj;
+            return Objects.equals(deviceId, that.deviceId) &&
+                    Objects.equals(type, that.type) &&
+                    Objects.equals(buckets, that.buckets);
+
+        }
+        return false;
+    }
+
 }
\ No newline at end of file
diff --git a/core/api/src/main/java/org/onosproject/net/group/Group.java b/core/api/src/main/java/org/onosproject/net/group/Group.java
index f7fa507..b7872de 100644
--- a/core/api/src/main/java/org/onosproject/net/group/Group.java
+++ b/core/api/src/main/java/org/onosproject/net/group/Group.java
@@ -26,6 +26,10 @@
      */
     public enum GroupState {
         /**
+         * Group create request is queued as group AUDIT is in progress.
+         */
+        WAITING_AUDIT_COMPLETE,
+        /**
          * Group create request is processed by ONOS and not yet
          * received the confirmation from data plane.
          */
@@ -81,4 +85,11 @@
      * @return number of bytes
      */
     long bytes();
+
+    /**
+     * Returns the number of flow rules or other groups reference this group.
+     *
+     * @return number of flow rules or other groups pointing to this group
+     */
+    long referenceCount();
 }
diff --git a/core/api/src/main/java/org/onosproject/net/group/GroupBuckets.java b/core/api/src/main/java/org/onosproject/net/group/GroupBuckets.java
index 10f4eca..5ca8f30 100644
--- a/core/api/src/main/java/org/onosproject/net/group/GroupBuckets.java
+++ b/core/api/src/main/java/org/onosproject/net/group/GroupBuckets.java
@@ -45,4 +45,25 @@
         return buckets;
     }
 
+    @Override
+    public int hashCode() {
+        int result = 17;
+        int combinedHash = 0;
+        for (GroupBucket bucket:buckets) {
+            combinedHash = combinedHash + bucket.hashCode();
+        }
+        result = 31 * result + combinedHash;
+
+        return result;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (obj instanceof GroupBuckets) {
+            return (this.buckets.containsAll(((GroupBuckets) obj).buckets) &&
+                    ((GroupBuckets) obj).buckets.containsAll(this.buckets));
+        }
+        return false;
+    }
+
 }
\ No newline at end of file
diff --git a/core/api/src/main/java/org/onosproject/net/group/GroupOperation.java b/core/api/src/main/java/org/onosproject/net/group/GroupOperation.java
index 44d7e88..5a66aca 100644
--- a/core/api/src/main/java/org/onosproject/net/group/GroupOperation.java
+++ b/core/api/src/main/java/org/onosproject/net/group/GroupOperation.java
@@ -17,6 +17,8 @@
 
 import static com.google.common.base.Preconditions.checkNotNull;
 
+import java.util.Objects;
+
 import org.onosproject.core.GroupId;
 
 /**
@@ -142,4 +144,37 @@
     public GroupBuckets buckets() {
         return this.buckets;
     }
+
+    @Override
+    /*
+     * The deviceId, type and buckets are used for hash.
+     *
+     * (non-Javadoc)
+     * @see java.lang.Object#equals(java.lang.Object)
+     */
+    public int hashCode() {
+        return (buckets != null) ? Objects.hash(groupId, opType, buckets) :
+            Objects.hash(groupId, opType);
+    }
+
+    @Override
+    /*
+     * The deviceId, type and buckets should be same.
+     *
+     * (non-Javadoc)
+     * @see java.lang.Object#equals(java.lang.Object)
+     */
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+       if (obj instanceof GroupOperation) {
+           GroupOperation that = (GroupOperation) obj;
+           return Objects.equals(groupId, that.groupId) &&
+                   Objects.equals(opType, that.opType) &&
+                   Objects.equals(buckets, that.buckets);
+
+        }
+        return false;
+    }
 }
\ No newline at end of file
diff --git a/core/api/src/main/java/org/onosproject/net/group/GroupProviderRegistry.java b/core/api/src/main/java/org/onosproject/net/group/GroupProviderRegistry.java
new file mode 100644
index 0000000..d45789d
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/net/group/GroupProviderRegistry.java
@@ -0,0 +1,25 @@
+/*
+ * 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;
+
+import org.onosproject.net.provider.ProviderRegistry;
+
+/**
+ * Abstraction for a group provider registry.
+ */
+public interface GroupProviderRegistry
+        extends ProviderRegistry<GroupProvider, GroupProviderService> {
+}
diff --git a/core/api/src/main/java/org/onosproject/net/group/GroupService.java b/core/api/src/main/java/org/onosproject/net/group/GroupService.java
index 1fd9984..8502aea 100644
--- a/core/api/src/main/java/org/onosproject/net/group/GroupService.java
+++ b/core/api/src/main/java/org/onosproject/net/group/GroupService.java
@@ -16,7 +16,6 @@
 package org.onosproject.net.group;
 
 import org.onosproject.core.ApplicationId;
-import org.onosproject.net.Device;
 import org.onosproject.net.DeviceId;
 
 /**
@@ -27,7 +26,7 @@
  * specified in a group.
  * "group" can also be used for grouping common actions of different flows,
  * so that in some scenarios only one group entry required to be modified
- * for all the referencing flow entries instead of modifying all of them
+ * for all the referencing flow entries instead of modifying all of them.
  *
  * This implements semantics of a distributed authoritative group store
  * where the master copy of the groups lies with the controller and
@@ -60,7 +59,7 @@
      * 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
+     * this group in data plane.
      *
      * @param deviceId device identifier
      * @param appCookie application cookie to be used for lookup
@@ -73,7 +72,7 @@
      * Appends 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
+     * 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
@@ -91,7 +90,7 @@
      * Removes 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
+     * 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
@@ -99,7 +98,7 @@
      * @param newCookie immutable cookie to be used post update operation
      * @param appId Application Id
      */
-    void removeBucketsFromGroup(Device deviceId,
+    void removeBucketsFromGroup(DeviceId deviceId,
                                 GroupKey oldCookie,
                                 GroupBuckets buckets,
                                 GroupKey newCookie,
@@ -109,13 +108,13 @@
      * Deletes 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
+     * operation on the device.
      *
      * @param deviceId device identifier
      * @param appCookie application cookie to be used for lookup
      * @param appId Application Id
      */
-    void removeGroup(Device deviceId, GroupKey appCookie, ApplicationId appId);
+    void removeGroup(DeviceId deviceId, GroupKey appCookie, ApplicationId appId);
 
     /**
      * Retrieves all groups created by an application in the specified device
@@ -125,7 +124,7 @@
      * @param appId application id
      * @return collection of immutable group objects created by the application
      */
-    Iterable<Group> getGroups(Device deviceId, ApplicationId appId);
+    Iterable<Group> getGroups(DeviceId deviceId, ApplicationId appId);
 
     /**
      * Adds the specified group listener.
diff --git a/core/api/src/main/java/org/onosproject/net/group/GroupStore.java b/core/api/src/main/java/org/onosproject/net/group/GroupStore.java
index 22914f9..2fc7030 100644
--- a/core/api/src/main/java/org/onosproject/net/group/GroupStore.java
+++ b/core/api/src/main/java/org/onosproject/net/group/GroupStore.java
@@ -73,12 +73,14 @@
      * @param deviceId the device ID
      * @param oldAppCookie the current group key
      * @param type update type
-     * @param newGroupDesc group description with updates
+     * @param newBuckets group buckets for updates
+     * @param newAppCookie optional new group key
      */
     void updateGroupDescription(DeviceId deviceId,
                                 GroupKey oldAppCookie,
                                 UpdateType type,
-                                GroupDescription newGroupDesc);
+                                GroupBuckets newBuckets,
+                                GroupKey newAppCookie);
 
     /**
      * Triggers deleting the existing group entry.
@@ -102,4 +104,43 @@
      * @param group group entry
      */
     void removeGroupEntry(Group group);
+
+    /**
+     * A group entry that is present in switch but not in the store.
+     *
+     * @param group group entry
+     */
+    void addOrUpdateExtraneousGroupEntry(Group group);
+
+    /**
+     * Remove the group entry from extraneous database.
+     *
+     * @param group group entry
+     */
+    void removeExtraneousGroupEntry(Group group);
+
+    /**
+     * Returns the extraneous groups associated with a device.
+     *
+     * @param deviceId the device ID
+     *
+     * @return the extraneous group entries
+     */
+    Iterable<Group> getExtraneousGroups(DeviceId deviceId);
+
+    /**
+     * Indicates the first group audit is completed.
+     *
+     * @param deviceId the device ID
+     */
+    void deviceInitialAuditCompleted(DeviceId deviceId);
+
+    /**
+     * Retrieves the initial group audit status for a device.
+     *
+     * @param deviceId the device ID
+     *
+     * @return initial group audit status
+     */
+    boolean deviceInitialAuditStatus(DeviceId deviceId);
 }
diff --git a/core/api/src/main/java/org/onosproject/net/group/StoredGroupEntry.java b/core/api/src/main/java/org/onosproject/net/group/StoredGroupEntry.java
index b3557b4..297663f 100644
--- a/core/api/src/main/java/org/onosproject/net/group/StoredGroupEntry.java
+++ b/core/api/src/main/java/org/onosproject/net/group/StoredGroupEntry.java
@@ -49,4 +49,10 @@
      */
     void setBytes(long bytes);
 
+    /**
+     * Sets number of flow rules or groups referencing this group entry.
+     *
+     * @param referenceCount reference count
+     */
+    void setReferenceCount(long referenceCount);
 }
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
new file mode 100644
index 0000000..f54f85e
--- /dev/null
+++ 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);
+            }
+        }
+    }
+}
diff --git a/core/net/src/main/java/org/onosproject/net/group/impl/package-info.java b/core/net/src/main/java/org/onosproject/net/group/impl/package-info.java
new file mode 100644
index 0000000..641ab44
--- /dev/null
+++ b/core/net/src/main/java/org/onosproject/net/group/impl/package-info.java
@@ -0,0 +1,20 @@
+/*
+ * 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.
+ */
+
+/**
+ * Core subsystem for group state.
+ */
+package org.onosproject.net.group.impl;
\ No newline at end of file
diff --git a/core/net/src/test/java/org/onosproject/net/group/impl/GroupManagerTest.java b/core/net/src/test/java/org/onosproject/net/group/impl/GroupManagerTest.java
new file mode 100644
index 0000000..2e1bd21
--- /dev/null
+++ b/core/net/src/test/java/org/onosproject/net/group/impl/GroupManagerTest.java
@@ -0,0 +1,400 @@
+/*
+ * 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.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotEquals;
+import static org.junit.Assert.assertTrue;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.onlab.packet.MacAddress;
+import org.onosproject.core.ApplicationId;
+import org.onosproject.core.DefaultApplicationId;
+import org.onosproject.core.DefaultGroupId;
+import org.onosproject.core.GroupId;
+import org.onosproject.event.impl.TestEventDispatcher;
+import org.onosproject.net.DeviceId;
+import org.onosproject.net.PortNumber;
+import org.onosproject.net.flow.DefaultTrafficTreatment;
+import org.onosproject.net.flow.TrafficTreatment;
+import org.onosproject.net.group.DefaultGroup;
+import org.onosproject.net.group.DefaultGroupBucket;
+import org.onosproject.net.group.DefaultGroupDescription;
+import org.onosproject.net.group.Group;
+import org.onosproject.net.group.GroupBucket;
+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.StoredGroupEntry;
+import org.onosproject.net.provider.AbstractProvider;
+import org.onosproject.net.provider.ProviderId;
+import org.onosproject.store.trivial.impl.SimpleGroupStore;
+
+import com.google.common.collect.Iterables;
+
+/**
+ * Test codifying the group service & group provider service contracts.
+ */
+public class GroupManagerTest {
+
+    private static final ProviderId PID = new ProviderId("of", "groupfoo");
+    private static final DeviceId DID = DeviceId.deviceId("of:001");
+
+    private GroupManager mgr;
+    private GroupService groupService;
+    private GroupProviderRegistry providerRegistry;
+    private TestGroupListener internalListener = new TestGroupListener();
+    private GroupListener listener = internalListener;
+    private TestGroupProvider internalProvider;
+    private GroupProvider provider;
+    private GroupProviderService providerService;
+    private ApplicationId appId;
+
+    @Before
+    public void setUp() {
+        mgr = new GroupManager();
+        groupService = mgr;
+        mgr.store = new SimpleGroupStore();
+        mgr.eventDispatcher = new TestEventDispatcher();
+        providerRegistry = mgr;
+
+        mgr.activate();
+        mgr.addListener(listener);
+
+        internalProvider = new TestGroupProvider(PID);
+        provider = internalProvider;
+        providerService = providerRegistry.register(provider);
+        appId = new DefaultApplicationId(2, "org.groupmanager.test");
+        assertTrue("provider should be registered",
+                   providerRegistry.getProviders().contains(provider.id()));
+    }
+
+    @After
+    public void tearDown() {
+        providerRegistry.unregister(provider);
+        assertFalse("provider should not be registered",
+                    providerRegistry.getProviders().contains(provider.id()));
+        mgr.removeListener(listener);
+        mgr.deactivate();
+        mgr.eventDispatcher = null;
+    }
+
+    private class TestGroupKey implements GroupKey {
+        private String groupId;
+
+        public TestGroupKey(String id) {
+            this.groupId = id;
+        }
+
+        public String id() {
+            return this.groupId;
+        }
+
+        @Override
+        public int hashCode() {
+            return groupId.hashCode();
+        }
+
+        @Override
+        public boolean equals(Object obj) {
+            if (obj instanceof TestGroupKey) {
+                return this.groupId.equals(((TestGroupKey) obj).id());
+            }
+            return false;
+        }
+    }
+
+    /**
+     * Tests group service north bound and south bound interfaces.
+     * The following operations are tested:
+     * a)Tests group creation before the device group AUDIT completes
+     * b)Tests initial device group AUDIT process
+     * c)Tests deletion process of any extraneous groups
+     * d)Tests execution of any pending group creation requests
+     * after the device group AUDIT completes
+     * e)Tests re-apply process of any missing groups
+     * f)Tests event notifications after receiving confirmation for
+     * any operations from data plane
+     * g)Tests group bucket modifications (additions and deletions)
+     * h)Tests group deletion
+     */
+    @Test
+    public void testGroupService() {
+        PortNumber[] ports1 = {PortNumber.portNumber(31),
+                               PortNumber.portNumber(32)};
+        PortNumber[] ports2 = {PortNumber.portNumber(41),
+                               PortNumber.portNumber(42)};
+        // Test Group creation before AUDIT process
+        TestGroupKey key = new TestGroupKey("group1BeforeAudit");
+        List<GroupBucket> buckets = new ArrayList<GroupBucket>();
+        List<PortNumber> outPorts = new ArrayList<PortNumber>();
+        outPorts.addAll(Arrays.asList(ports1));
+        outPorts.addAll(Arrays.asList(ports2));
+        for (PortNumber portNumber: outPorts) {
+            TrafficTreatment.Builder tBuilder = DefaultTrafficTreatment.builder();
+            tBuilder.setOutput(portNumber)
+                    .setEthDst(MacAddress.valueOf("00:00:00:00:00:02"))
+                    .setEthSrc(MacAddress.valueOf("00:00:00:00:00:01"))
+                    .pushMpls()
+                    .setMpls(106);
+            buckets.add(DefaultGroupBucket.createSelectGroupBucket(
+                                                        tBuilder.build()));
+        }
+        GroupBuckets groupBuckets = new GroupBuckets(buckets);
+        GroupDescription newGroupDesc = new DefaultGroupDescription(DID,
+                                                                    Group.Type.SELECT,
+                                                                    groupBuckets,
+                                                                    key,
+                                                                    appId);
+        groupService.addGroup(newGroupDesc);
+        internalProvider.validate(DID, null);
+        assertEquals(null, groupService.getGroup(DID, key));
+        assertEquals(0, Iterables.size(groupService.getGroups(DID, appId)));
+
+        // Test initial group audit process
+        GroupId gId1 = new DefaultGroupId(1);
+        Group group1 = createSouthboundGroupEntry(gId1,
+                                                  Arrays.asList(ports1),
+                                                  0);
+        GroupId gId2 = new DefaultGroupId(2);
+        // Non zero reference count will make the group manager to queue
+        // the extraneous groups until reference count is zero.
+        Group group2 = createSouthboundGroupEntry(gId2,
+                                                  Arrays.asList(ports2),
+                                                  2);
+        List<Group> groupEntries = Arrays.asList(group1, group2);
+        providerService.pushGroupMetrics(DID, groupEntries);
+        // First group metrics would trigger the device audit completion
+        // post which all pending group requests are also executed.
+        Group createdGroup = groupService.getGroup(DID, key);
+        int createdGroupId = createdGroup.id().id();
+        assertNotEquals(gId1.id(), createdGroupId);
+        assertNotEquals(gId2.id(), createdGroupId);
+        List<GroupOperation> expectedGroupOps = Arrays.asList(
+                            GroupOperation.createDeleteGroupOperation(gId1,
+                                                          Group.Type.SELECT),
+                            GroupOperation.createAddGroupOperation(
+                                           createdGroup.id(),
+                                           Group.Type.SELECT,
+                                           groupBuckets));
+        internalProvider.validate(DID, expectedGroupOps);
+
+        group1 = createSouthboundGroupEntry(gId1,
+                                            Arrays.asList(ports1),
+                                            0);
+        group2 = createSouthboundGroupEntry(gId2,
+                                            Arrays.asList(ports2),
+                                            0);
+        groupEntries = Arrays.asList(group1, group2);
+        providerService.pushGroupMetrics(DID, groupEntries);
+        expectedGroupOps = Arrays.asList(
+                GroupOperation.createDeleteGroupOperation(gId1,
+                                                          Group.Type.SELECT),
+                GroupOperation.createDeleteGroupOperation(gId2,
+                                                          Group.Type.SELECT),
+                GroupOperation.createAddGroupOperation(createdGroup.id(),
+                                                       Group.Type.SELECT,
+                                                       groupBuckets));
+        internalProvider.validate(DID, expectedGroupOps);
+
+        createdGroup = new DefaultGroup(createdGroup.id(),
+                                        DID,
+                                        Group.Type.SELECT,
+                                        groupBuckets);
+        groupEntries = Arrays.asList(createdGroup);
+        providerService.pushGroupMetrics(DID, groupEntries);
+        internalListener.validateEvent(Arrays.asList(GroupEvent.Type.GROUP_ADDED));
+
+        // Test group add bucket operations
+        TestGroupKey addKey = new TestGroupKey("group1AddBuckets");
+        PortNumber[] addPorts = {PortNumber.portNumber(51),
+                                 PortNumber.portNumber(52)};
+        outPorts.clear();
+        outPorts.addAll(Arrays.asList(addPorts));
+        List<GroupBucket> addBuckets = new ArrayList<GroupBucket>();
+        for (PortNumber portNumber: outPorts) {
+            TrafficTreatment.Builder tBuilder = DefaultTrafficTreatment.builder();
+            tBuilder.setOutput(portNumber)
+                    .setEthDst(MacAddress.valueOf("00:00:00:00:00:02"))
+                    .setEthSrc(MacAddress.valueOf("00:00:00:00:00:01"))
+                    .pushMpls()
+                    .setMpls(106);
+            addBuckets.add(DefaultGroupBucket.createSelectGroupBucket(
+                                                        tBuilder.build()));
+            buckets.add(DefaultGroupBucket.createSelectGroupBucket(
+                                                        tBuilder.build()));
+        }
+        GroupBuckets groupAddBuckets = new GroupBuckets(addBuckets);
+        groupService.addBucketsToGroup(DID,
+                                       key,
+                                       groupAddBuckets,
+                                       addKey,
+                                       appId);
+        GroupBuckets updatedBuckets = new GroupBuckets(buckets);
+        expectedGroupOps = Arrays.asList(
+               GroupOperation.createModifyGroupOperation(createdGroup.id(),
+                                                         Group.Type.SELECT,
+                                                         updatedBuckets));
+        internalProvider.validate(DID, expectedGroupOps);
+        Group existingGroup = groupService.getGroup(DID, addKey);
+        groupEntries = Arrays.asList(existingGroup);
+        providerService.pushGroupMetrics(DID, groupEntries);
+        internalListener.validateEvent(Arrays.asList(GroupEvent.Type.GROUP_UPDATED));
+
+        // Test group remove bucket operations
+        TestGroupKey removeKey = new TestGroupKey("group1RemoveBuckets");
+        PortNumber[] removePorts = {PortNumber.portNumber(31),
+                                 PortNumber.portNumber(32)};
+        outPorts.clear();
+        outPorts.addAll(Arrays.asList(removePorts));
+        List<GroupBucket> removeBuckets = new ArrayList<GroupBucket>();
+        for (PortNumber portNumber: outPorts) {
+            TrafficTreatment.Builder tBuilder = DefaultTrafficTreatment.builder();
+            tBuilder.setOutput(portNumber)
+                    .setEthDst(MacAddress.valueOf("00:00:00:00:00:02"))
+                    .setEthSrc(MacAddress.valueOf("00:00:00:00:00:01"))
+                    .pushMpls()
+                    .setMpls(106);
+            removeBuckets.add(DefaultGroupBucket.createSelectGroupBucket(
+                                                        tBuilder.build()));
+            buckets.remove(DefaultGroupBucket.createSelectGroupBucket(
+                                                        tBuilder.build()));
+        }
+        GroupBuckets groupRemoveBuckets = new GroupBuckets(removeBuckets);
+        groupService.removeBucketsFromGroup(DID,
+                                            addKey,
+                                            groupRemoveBuckets,
+                                            removeKey,
+                                            appId);
+        updatedBuckets = new GroupBuckets(buckets);
+        expectedGroupOps = Arrays.asList(
+               GroupOperation.createModifyGroupOperation(createdGroup.id(),
+                                                         Group.Type.SELECT,
+                                                         updatedBuckets));
+        internalProvider.validate(DID, expectedGroupOps);
+        existingGroup = groupService.getGroup(DID, removeKey);
+        groupEntries = Arrays.asList(existingGroup);
+        providerService.pushGroupMetrics(DID, groupEntries);
+        internalListener.validateEvent(Arrays.asList(GroupEvent.Type.GROUP_UPDATED));
+
+        // Test group remove operations
+        groupService.removeGroup(DID, removeKey, appId);
+        expectedGroupOps = Arrays.asList(
+             GroupOperation.createDeleteGroupOperation(createdGroup.id(),
+                                                       Group.Type.SELECT));
+        internalProvider.validate(DID, expectedGroupOps);
+        groupEntries = Collections.emptyList();
+        providerService.pushGroupMetrics(DID, groupEntries);
+        internalListener.validateEvent(Arrays.asList(GroupEvent.Type.GROUP_REMOVED));
+    }
+
+    private Group createSouthboundGroupEntry(GroupId gId,
+                                             List<PortNumber> ports,
+                                             long referenceCount) {
+        List<PortNumber> outPorts = new ArrayList<PortNumber>();
+        outPorts.addAll(ports);
+
+        List<GroupBucket> buckets = new ArrayList<GroupBucket>();
+        for (PortNumber portNumber: outPorts) {
+            TrafficTreatment.Builder tBuilder = DefaultTrafficTreatment.builder();
+            tBuilder.setOutput(portNumber)
+                    .setEthDst(MacAddress.valueOf("00:00:00:00:00:02"))
+                    .setEthSrc(MacAddress.valueOf("00:00:00:00:00:01"))
+                    .pushMpls()
+                    .setMpls(106);
+            buckets.add(DefaultGroupBucket.createSelectGroupBucket(
+                                                        tBuilder.build()));
+        }
+        GroupBuckets groupBuckets = new GroupBuckets(buckets);
+        StoredGroupEntry group = new DefaultGroup(
+                            gId, DID, Group.Type.SELECT, groupBuckets);
+        group.setReferenceCount(referenceCount);
+        return group;
+    }
+
+    private static class TestGroupListener implements GroupListener {
+        final List<GroupEvent> events = new ArrayList<>();
+
+        @Override
+        public void event(GroupEvent event) {
+            events.add(event);
+        }
+
+        public void validateEvent(List<GroupEvent.Type> expectedEvents) {
+            int i = 0;
+            System.err.println("events :" + events);
+            for (GroupEvent e : events) {
+                assertEquals("unexpected event", expectedEvents.get(i), e.type());
+                i++;
+            }
+            assertEquals("mispredicted number of events",
+                         expectedEvents.size(), events.size());
+            events.clear();
+        }
+    }
+
+    private class TestGroupProvider
+                extends AbstractProvider implements GroupProvider {
+        DeviceId lastDeviceId;
+        List<GroupOperation> groupOperations = new ArrayList<GroupOperation>();
+
+        protected TestGroupProvider(ProviderId id) {
+            super(id);
+        }
+
+        @Override
+        public void performGroupOperation(DeviceId deviceId,
+                                          GroupOperations groupOps) {
+            lastDeviceId = deviceId;
+            groupOperations.addAll(groupOps.operations());
+        }
+
+        public void validate(DeviceId expectedDeviceId,
+                             List<GroupOperation> expectedGroupOps) {
+            if (expectedGroupOps == null) {
+                assertTrue("events generated", groupOperations.isEmpty());
+                return;
+            }
+
+            assertEquals(lastDeviceId, expectedDeviceId);
+            assertTrue((this.groupOperations.containsAll(expectedGroupOps) &&
+                    expectedGroupOps.containsAll(groupOperations)));
+
+            groupOperations.clear();
+            lastDeviceId = null;
+        }
+
+    }
+
+}
+
+
diff --git a/core/store/trivial/src/main/java/org/onosproject/store/trivial/impl/SimpleGroupStore.java b/core/store/trivial/src/main/java/org/onosproject/store/trivial/impl/SimpleGroupStore.java
index c82ebc2..8c7de08 100644
--- a/core/store/trivial/src/main/java/org/onosproject/store/trivial/impl/SimpleGroupStore.java
+++ b/core/store/trivial/src/main/java/org/onosproject/store/trivial/impl/SimpleGroupStore.java
@@ -19,6 +19,7 @@
 import static org.slf4j.LoggerFactory.getLogger;
 
 import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.List;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
@@ -62,11 +63,21 @@
 
     private final Logger log = getLogger(getClass());
 
+    private final int dummyId = 0xffffffff;
+    private final GroupId dummyGroupId = new DefaultGroupId(dummyId);
+
     // inner Map is per device group table
     private final ConcurrentMap<DeviceId, ConcurrentMap<GroupKey, StoredGroupEntry>>
             groupEntriesByKey = new ConcurrentHashMap<>();
     private final ConcurrentMap<DeviceId, ConcurrentMap<GroupId, StoredGroupEntry>>
             groupEntriesById = new ConcurrentHashMap<>();
+    private final ConcurrentMap<DeviceId, ConcurrentMap<GroupKey, StoredGroupEntry>>
+            pendingGroupEntriesByKey = new ConcurrentHashMap<>();
+    private final ConcurrentMap<DeviceId, ConcurrentMap<GroupId, Group>>
+        extraneousGroupEntriesById = new ConcurrentHashMap<>();
+
+    private final HashMap<DeviceId, Boolean> deviceAuditStatus =
+            new HashMap<DeviceId, Boolean>();
 
     private final AtomicInteger groupIdGen = new AtomicInteger();
 
@@ -82,14 +93,26 @@
         log.info("Stopped");
     }
 
-    private static NewConcurrentHashMap<GroupKey, StoredGroupEntry> lazyEmptyGroupKeyTable() {
+    private static NewConcurrentHashMap<GroupKey, StoredGroupEntry>
+                        lazyEmptyGroupKeyTable() {
         return NewConcurrentHashMap.<GroupKey, StoredGroupEntry>ifNeeded();
     }
 
-    private static NewConcurrentHashMap<GroupId, StoredGroupEntry> lazyEmptyGroupIdTable() {
+    private static NewConcurrentHashMap<GroupId, StoredGroupEntry>
+                        lazyEmptyGroupIdTable() {
         return NewConcurrentHashMap.<GroupId, StoredGroupEntry>ifNeeded();
     }
 
+    private static NewConcurrentHashMap<GroupKey, StoredGroupEntry>
+                        lazyEmptyPendingGroupKeyTable() {
+        return NewConcurrentHashMap.<GroupKey, StoredGroupEntry>ifNeeded();
+    }
+
+    private static NewConcurrentHashMap<GroupId, Group>
+                        lazyEmptyExtraneousGroupIdTable() {
+        return NewConcurrentHashMap.<GroupId, Group>ifNeeded();
+    }
+
     /**
      * Returns the group key table for specified device.
      *
@@ -113,6 +136,31 @@
     }
 
     /**
+     * Returns the pending group key table for specified device.
+     *
+     * @param deviceId identifier of the device
+     * @return Map representing group key table of given device.
+     */
+    private ConcurrentMap<GroupKey, StoredGroupEntry>
+                    getPendingGroupKeyTable(DeviceId deviceId) {
+        return createIfAbsentUnchecked(pendingGroupEntriesByKey,
+                                       deviceId, lazyEmptyPendingGroupKeyTable());
+    }
+
+    /**
+     * Returns the extraneous group id table for specified device.
+     *
+     * @param deviceId identifier of the device
+     * @return Map representing group key table of given device.
+     */
+    private ConcurrentMap<GroupId, Group>
+                getExtraneousGroupIdTable(DeviceId deviceId) {
+        return createIfAbsentUnchecked(extraneousGroupEntriesById,
+                                       deviceId,
+                                       lazyEmptyExtraneousGroupIdTable());
+    }
+
+    /**
      * Returns the number of groups for the specified device in the store.
      *
      * @return number of groups for the specified device
@@ -133,20 +181,16 @@
     @Override
     public Iterable<Group> getGroups(DeviceId deviceId) {
         // flatten and make iterator unmodifiable
-        if (groupEntriesByKey.get(deviceId) != null) {
-            return FluentIterable.from(groupEntriesByKey.get(deviceId).values())
-                .transform(
-                        new Function<StoredGroupEntry, Group>() {
+        return FluentIterable.from(getGroupKeyTable(deviceId).values())
+            .transform(
+                    new Function<StoredGroupEntry, Group>() {
 
-                            @Override
-                            public Group apply(
-                                    StoredGroupEntry input) {
-                                return input;
-                            }
-                        });
-        } else {
-            return null;
-        }
+                        @Override
+                        public Group apply(
+                                StoredGroupEntry input) {
+                            return input;
+                        }
+                    });
     }
 
     /**
@@ -164,6 +208,30 @@
                       null;
     }
 
+    private int getFreeGroupIdValue(DeviceId deviceId) {
+        int freeId = groupIdGen.incrementAndGet();
+
+        while (true) {
+            Group existing = (
+                    groupEntriesById.get(deviceId) != null) ?
+                    groupEntriesById.get(deviceId).get(new DefaultGroupId(freeId)) :
+                    null;
+            if (existing == null) {
+                existing = (
+                        extraneousGroupEntriesById.get(deviceId) != null) ?
+                        extraneousGroupEntriesById.get(deviceId).
+                        get(new DefaultGroupId(freeId)) :
+                        null;
+            }
+            if (existing != null) {
+                freeId = groupIdGen.incrementAndGet();
+            } else {
+                break;
+            }
+        }
+        return freeId;
+    }
+
     /**
      * Stores a new group entry using the information from group description.
      *
@@ -171,16 +239,32 @@
      */
     @Override
     public void storeGroupDescription(GroupDescription groupDesc) {
-        /* Check if a group is existing with the same key */
+        // Check if a group is existing with the same key
         if (getGroup(groupDesc.deviceId(), groupDesc.appCookie()) != null) {
             return;
         }
 
-        /* Get a new group identifier */
-        GroupId id = new DefaultGroupId(groupIdGen.incrementAndGet());
-        /* Create a group entry object */
+        if (deviceAuditStatus.get(groupDesc.deviceId()) == null) {
+            // Device group audit has not completed yet
+            // Add this group description to pending group key table
+            // Create a group entry object with Dummy Group ID
+            StoredGroupEntry group = new DefaultGroup(dummyGroupId, groupDesc);
+            group.setState(GroupState.WAITING_AUDIT_COMPLETE);
+            ConcurrentMap<GroupKey, StoredGroupEntry> pendingKeyTable =
+                    getPendingGroupKeyTable(groupDesc.deviceId());
+            pendingKeyTable.put(groupDesc.appCookie(), group);
+            return;
+        }
+
+        storeGroupDescriptionInternal(groupDesc);
+    }
+
+    private void storeGroupDescriptionInternal(GroupDescription groupDesc) {
+        // Get a new group identifier
+        GroupId id = new DefaultGroupId(getFreeGroupIdValue(groupDesc.deviceId()));
+        // Create a group entry object
         StoredGroupEntry group = new DefaultGroup(id, groupDesc);
-        /* Insert the newly created group entry into concurrent key and id maps */
+        // Insert the newly created group entry into concurrent key and id maps
         ConcurrentMap<GroupKey, StoredGroupEntry> keyTable =
                 getGroupKeyTable(groupDesc.deviceId());
         keyTable.put(groupDesc.appCookie(), group);
@@ -198,14 +282,16 @@
      * @param deviceId the device ID
      * @param oldAppCookie the current group key
      * @param type update type
-     * @param newGroupDesc group description with updates
+     * @param newBuckets group buckets for updates
+     * @param newAppCookie optional new group key
      */
     @Override
     public void updateGroupDescription(DeviceId deviceId,
                                 GroupKey oldAppCookie,
                                 UpdateType type,
-                                GroupDescription newGroupDesc) {
-        /* Check if a group is existing with the provided key */
+                                GroupBuckets newBuckets,
+                                GroupKey newAppCookie) {
+        // Check if a group is existing with the provided key
         Group oldGroup = getGroup(deviceId, oldAppCookie);
         if (oldGroup == null) {
             return;
@@ -213,15 +299,16 @@
 
         List<GroupBucket> newBucketList = getUpdatedBucketList(oldGroup,
                                                                type,
-                                               newGroupDesc.buckets());
+                                                               newBuckets);
         if (newBucketList != null) {
-            /* Create a new group object from the old group */
+            // Create a new group object from the old group
             GroupBuckets updatedBuckets = new GroupBuckets(newBucketList);
+            GroupKey newCookie = (newAppCookie != null) ? newAppCookie : oldAppCookie;
             GroupDescription updatedGroupDesc = new DefaultGroupDescription(
                                                         oldGroup.deviceId(),
                                                         oldGroup.type(),
                                                         updatedBuckets,
-                                                        newGroupDesc.appCookie(),
+                                                        newCookie,
                                                         oldGroup.appId());
             StoredGroupEntry newGroup = new DefaultGroup(oldGroup.id(),
                                                      updatedGroupDesc);
@@ -229,9 +316,7 @@
             newGroup.setLife(oldGroup.life());
             newGroup.setPackets(oldGroup.packets());
             newGroup.setBytes(oldGroup.bytes());
-            /* Remove the old entry from maps and add new entry
-             * using new key
-             */
+            // Remove the old entry from maps and add new entry using new key
             ConcurrentMap<GroupKey, StoredGroupEntry> keyTable =
                     getGroupKeyTable(oldGroup.deviceId());
             ConcurrentMap<GroupId, StoredGroupEntry> idTable =
@@ -253,9 +338,8 @@
         boolean groupDescUpdated = false;
 
         if (type == UpdateType.ADD) {
-            /* Check if the any of the new buckets are part of the
-             * old bucket list
-             */
+            // Check if the any of the new buckets are part of
+            // the old bucket list
             for (GroupBucket addBucket:buckets.buckets()) {
                 if (!newBucketList.contains(addBucket)) {
                     newBucketList.add(addBucket);
@@ -263,9 +347,8 @@
                 }
             }
         } else if (type == UpdateType.REMOVE) {
-            /* Check if the to be removed buckets are part of the
-             * old bucket list
-             */
+            // Check if the to be removed buckets are part of the
+            // old bucket list
             for (GroupBucket removeBucket:buckets.buckets()) {
                 if (newBucketList.contains(removeBucket)) {
                     newBucketList.remove(removeBucket);
@@ -290,7 +373,7 @@
     @Override
     public void deleteGroupDescription(DeviceId deviceId,
                                 GroupKey appCookie) {
-        /* Check if a group is existing with the provided key */
+        // Check if a group is existing with the provided key
         StoredGroupEntry existing = (groupEntriesByKey.get(deviceId) != null) ?
                            groupEntriesByKey.get(deviceId).get(appCookie) :
                            null;
@@ -362,4 +445,56 @@
             notifyDelegate(new GroupEvent(Type.GROUP_REMOVED, existing));
         }
     }
+
+    @Override
+    public void deviceInitialAuditCompleted(DeviceId deviceId) {
+        synchronized (deviceAuditStatus) {
+            deviceAuditStatus.putIfAbsent(deviceId, true);
+            // Execute all pending group requests
+            ConcurrentMap<GroupKey, StoredGroupEntry> pendingGroupRequests =
+                    getPendingGroupKeyTable(deviceId);
+            for (Group group:pendingGroupRequests.values()) {
+                GroupDescription tmp = new DefaultGroupDescription(
+                             group.deviceId(),
+                             group.type(),
+                             group.buckets(),
+                             group.appCookie(),
+                             group.appId());
+                storeGroupDescriptionInternal(tmp);
+            }
+            getPendingGroupKeyTable(deviceId).clear();
+        }
+    }
+
+    @Override
+    public boolean deviceInitialAuditStatus(DeviceId deviceId) {
+        synchronized (deviceAuditStatus) {
+            return (deviceAuditStatus.get(deviceId) != null) ? true : false;
+        }
+    }
+
+    @Override
+    public void addOrUpdateExtraneousGroupEntry(Group group) {
+        ConcurrentMap<GroupId, Group> extraneousIdTable =
+                getExtraneousGroupIdTable(group.deviceId());
+        extraneousIdTable.put(group.id(), group);
+        // Check the reference counter
+        if (group.referenceCount() == 0) {
+            notifyDelegate(new GroupEvent(Type.GROUP_REMOVE_REQUESTED, group));
+        }
+    }
+
+    @Override
+    public void removeExtraneousGroupEntry(Group group) {
+        ConcurrentMap<GroupId, Group> extraneousIdTable =
+                getExtraneousGroupIdTable(group.deviceId());
+        extraneousIdTable.remove(group.id());
+    }
+
+    @Override
+    public Iterable<Group> getExtraneousGroups(DeviceId deviceId) {
+        // flatten and make iterator unmodifiable
+        return FluentIterable.from(
+                  getExtraneousGroupIdTable(deviceId).values());
+    }
 }
diff --git a/core/store/trivial/src/test/java/org/onosproject/store/trivial/impl/SimpleGroupStoreTest.java b/core/store/trivial/src/test/java/org/onosproject/store/trivial/impl/SimpleGroupStoreTest.java
index b1f03f4..277e1ca 100644
--- a/core/store/trivial/src/test/java/org/onosproject/store/trivial/impl/SimpleGroupStoreTest.java
+++ b/core/store/trivial/src/test/java/org/onosproject/store/trivial/impl/SimpleGroupStoreTest.java
@@ -40,8 +40,10 @@
 import org.onosproject.net.group.GroupDescription;
 import org.onosproject.net.group.GroupEvent;
 import org.onosproject.net.group.GroupKey;
-import org.onosproject.net.group.GroupStoreDelegate;
 import org.onosproject.net.group.GroupStore.UpdateType;
+import org.onosproject.net.group.GroupStoreDelegate;
+
+import com.google.common.collect.Iterables;
 
 /**
  * Test of the simple DeviceStore implementation.
@@ -135,8 +137,24 @@
         }
     }
 
+    /**
+     * Tests group store operations. The following operations are tested:
+     * a)Tests device group audit completion status change
+     * b)Tests storeGroup operation
+     * c)Tests getGroupCount operation
+     * d)Tests getGroup operation
+     * e)Tests getGroups operation
+     * f)Tests addOrUpdateGroupEntry operation from southbound
+     * g)Tests updateGroupDescription for ADD operation from northbound
+     * h)Tests updateGroupDescription for REMOVE operation from northbound
+     * i)Tests deleteGroupDescription operation from northbound
+     * j)Tests removeGroupEntry operation from southbound
+     */
     @Test
     public void testGroupStoreOperations() {
+        // Set the Device AUDIT completed in the store
+        simpleGroupStore.deviceInitialAuditCompleted(D1);
+
         ApplicationId appId =
                 new DefaultApplicationId(2, "org.groupstore.test");
         TestGroupKey key = new TestGroupKey("group1");
@@ -169,17 +187,17 @@
                                                groupBuckets,
                                                GroupEvent.Type.GROUP_ADD_REQUESTED);
         simpleGroupStore.setDelegate(checkStoreGroupDelegate);
-        /* Testing storeGroup operation */
+        // Testing storeGroup operation
         simpleGroupStore.storeGroupDescription(groupDesc);
 
-        /* Testing getGroupCount operation */
+        // Testing getGroupCount operation
         assertEquals(1, simpleGroupStore.getGroupCount(D1));
 
-        /* Testing getGroup operation */
+        // Testing getGroup operation
         Group createdGroup = simpleGroupStore.getGroup(D1, key);
         checkStoreGroupDelegate.verifyGroupId(createdGroup.id());
 
-        /* Testing getGroups operation */
+        // Testing getGroups operation
         Iterable<Group> createdGroups = simpleGroupStore.getGroups(D1);
         int groupCount = 0;
         for (Group group:createdGroups) {
@@ -189,7 +207,7 @@
         assertEquals(1, groupCount);
         simpleGroupStore.unsetDelegate(checkStoreGroupDelegate);
 
-        /* Testing addOrUpdateGroupEntry operation from southbound */
+        // Testing addOrUpdateGroupEntry operation from southbound
         InternalGroupStoreDelegate addGroupEntryDelegate =
                 new InternalGroupStoreDelegate(key,
                                                groupBuckets,
@@ -198,7 +216,7 @@
         simpleGroupStore.addOrUpdateGroupEntry(createdGroup);
         simpleGroupStore.unsetDelegate(addGroupEntryDelegate);
 
-        /* Testing updateGroupDescription for ADD operation from northbound */
+        // Testing updateGroupDescription for ADD operation from northbound
         TestGroupKey addKey = new TestGroupKey("group1AddBuckets");
         PortNumber[] newNeighborPorts = {PortNumber.portNumber(41),
                                          PortNumber.portNumber(42)};
@@ -225,19 +243,14 @@
                                                updatedGroupBuckets,
                                                GroupEvent.Type.GROUP_UPDATE_REQUESTED);
         simpleGroupStore.setDelegate(updateGroupDescDelegate);
-        GroupDescription newGroupDesc = new DefaultGroupDescription(
-                                                 D1,
-                                                 Group.Type.SELECT,
-                                                 toAddGroupBuckets,
-                                                 addKey,
-                                                 appId);
         simpleGroupStore.updateGroupDescription(D1,
                                                 key,
                                                 UpdateType.ADD,
-                                                newGroupDesc);
+                                                toAddGroupBuckets,
+                                                addKey);
         simpleGroupStore.unsetDelegate(updateGroupDescDelegate);
 
-        /* Testing updateGroupDescription for REMOVE operation from northbound */
+        // Testing updateGroupDescription for REMOVE operation from northbound
         TestGroupKey removeKey = new TestGroupKey("group1RemoveBuckets");
         List<GroupBucket> toRemoveBuckets = new ArrayList<GroupBucket>();
         toRemoveBuckets.add(updatedGroupBuckets.buckets().get(0));
@@ -252,23 +265,18 @@
                                                remainingGroupBuckets,
                                                GroupEvent.Type.GROUP_UPDATE_REQUESTED);
         simpleGroupStore.setDelegate(removeGroupDescDelegate);
-        GroupDescription removeGroupDesc = new DefaultGroupDescription(
-                                                        D1,
-                                                        Group.Type.SELECT,
-                                                        toRemoveGroupBuckets,
-                                                        removeKey,
-                                                        appId);
         simpleGroupStore.updateGroupDescription(D1,
                                                 addKey,
                                                 UpdateType.REMOVE,
-                                                removeGroupDesc);
+                                                toRemoveGroupBuckets,
+                                                removeKey);
         simpleGroupStore.unsetDelegate(removeGroupDescDelegate);
 
-        /* Testing getGroup operation */
+        // Testing getGroup operation
         Group existingGroup = simpleGroupStore.getGroup(D1, removeKey);
         checkStoreGroupDelegate.verifyGroupId(existingGroup.id());
 
-        /* Testing addOrUpdateGroupEntry operation from southbound */
+        // Testing addOrUpdateGroupEntry operation from southbound
         InternalGroupStoreDelegate updateGroupEntryDelegate =
                 new InternalGroupStoreDelegate(removeKey,
                                                remainingGroupBuckets,
@@ -277,7 +285,7 @@
         simpleGroupStore.addOrUpdateGroupEntry(existingGroup);
         simpleGroupStore.unsetDelegate(updateGroupEntryDelegate);
 
-        /* Testing deleteGroupDescription operation from northbound */
+        // Testing deleteGroupDescription operation from northbound
         InternalGroupStoreDelegate deleteGroupDescDelegate =
                 new InternalGroupStoreDelegate(removeKey,
                                                remainingGroupBuckets,
@@ -286,7 +294,7 @@
         simpleGroupStore.deleteGroupDescription(D1, removeKey);
         simpleGroupStore.unsetDelegate(deleteGroupDescDelegate);
 
-        /* Testing removeGroupEntry operation from southbound */
+        // Testing removeGroupEntry operation from southbound
         InternalGroupStoreDelegate removeGroupEntryDelegate =
                 new InternalGroupStoreDelegate(removeKey,
                                                remainingGroupBuckets,
@@ -294,17 +302,10 @@
         simpleGroupStore.setDelegate(removeGroupEntryDelegate);
         simpleGroupStore.removeGroupEntry(existingGroup);
 
-        /* Testing getGroup operation */
+        // Testing getGroup operation
         existingGroup = simpleGroupStore.getGroup(D1, removeKey);
         assertEquals(null, existingGroup);
-        Iterable<Group> existingGroups  = simpleGroupStore.getGroups(D1);
-        groupCount = 0;
-        for (Group tmp:existingGroups) {
-            /* To avoid warning */
-            assertEquals(null, tmp);
-            groupCount++;
-        }
-        assertEquals(0, groupCount);
+        assertEquals(0, Iterables.size(simpleGroupStore.getGroups(D1)));
         assertEquals(0, simpleGroupStore.getGroupCount(D1));
 
         simpleGroupStore.unsetDelegate(removeGroupEntryDelegate);