diff --git a/core/api/src/main/java/org/onosproject/net/statistic/FlowStatisticService.java b/core/api/src/main/java/org/onosproject/net/statistic/FlowStatisticService.java
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+++ b/core/api/src/main/java/org/onosproject/net/statistic/FlowStatisticService.java
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+/*
+ * 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.statistic;
+
+import org.onosproject.net.ConnectPoint;
+import org.onosproject.net.Device;
+import org.onosproject.net.PortNumber;
+import org.onosproject.net.flow.TypedStoredFlowEntry;
+import org.onosproject.net.flow.instructions.Instruction;
+
+import java.util.List;
+import java.util.Map;
+
+/**
+ * Service for obtaining individual flow statistic information about device and link in the system.
+ * Basic statistics are obtained from the StatisticService
+ */
+public interface FlowStatisticService {
+
+    /**
+     * Obtain the summary load list for the device with the given link.
+     *
+     * @param device the Device  to query.
+     * @return map of summary flow entry load
+     */
+    Map<ConnectPoint, SummaryFlowEntryWithLoad> loadSummary(Device device);
+
+    /**
+     * Obtain the summary load for the device with the given link or port.
+     *
+     * @param device the Device to query.
+     * @param pNumber the port number to query.
+     * @return summary flow entry load
+     */
+    SummaryFlowEntryWithLoad loadSummary(Device device, PortNumber pNumber);
+
+    /**
+     * Obtain the set of the flow type and load list for the device with the given link.
+     *
+     * @param device the Device  to query.
+     * @param liveType the FlowLiveType  to filter, null means no filtering .
+     * @param instType the InstructionType to filter, null means no filtering.
+     * @return map of flow entry load
+     */
+    Map<ConnectPoint, List<TypedFlowEntryWithLoad>> loadAllByType(Device device,
+                                                                  TypedStoredFlowEntry.FlowLiveType liveType,
+                                                                  Instruction.Type instType);
+
+    /**
+     * Obtain the flow type and load list for the device with the given link or port.
+     *
+     * @param device the Device to query.
+     * @param pNumber the port number of the Device to query
+     * @param liveType the FlowLiveType  to filter, null means no filtering .
+     * @param instType the InstructionType to filter, null means no filtering.
+     * @return list of flow entry load
+     */
+    List<TypedFlowEntryWithLoad> loadAllByType(Device device, PortNumber pNumber,
+                                               TypedStoredFlowEntry.FlowLiveType liveType,
+                                               Instruction.Type instType);
+
+    /**
+     * Obtain the set of the flow type and load topn list for the device with the given link.
+     *
+     * @param device the Device  to query.
+     * @param liveType the FlowLiveType  to filter, null means no filtering .
+     * @param instType the InstructionType to filter, null means no filtering.
+     * @param topn the top number to filter, null means no filtering.
+     * @return map of flow entry load
+     */
+    Map<ConnectPoint, List<TypedFlowEntryWithLoad>> loadTopnByType(Device device,
+                                                                   TypedStoredFlowEntry.FlowLiveType liveType,
+                                                                   Instruction.Type instType,
+                                                                   int topn);
+
+    /**
+     * Obtain the flow type and load topn list for the device with the given link or port.
+     *
+     * @param device the Device  to query.
+     * @param pNumber the port number of the Device to query
+     * @param liveType the FlowLiveType  to filter, null means no filtering .
+     * @param instType the InstructionType to filter, null means no filtering.
+     * @return list of flow entry load
+     */
+    List<TypedFlowEntryWithLoad> loadTopnByType(Device device, PortNumber pNumber,
+                                                TypedStoredFlowEntry.FlowLiveType liveType,
+                                                Instruction.Type instType,
+                                                int topn);
+}
+
+