[ONOS-2233] Tunnel monitoring, measurement and observation

1. tunnel statistics interface

Change-Id: Iffac60ead5273b6a309552be7be10d1cc89bd1d6

+/*
+ *
+ *  * 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.incubator.net.tunnel;
+
+import java.time.Duration;
+import java.util.List;
+
+/**
+ * Statistics of a tunnel.
+ */
+public interface TunnelStatistics {
+
+    /**
+     * Returns the tunnel id.
+     *
+     * @return tunnelId id of tunnel
+     */
+    TunnelId id();
+
+    /**
+     * Returns the bandwidth utilization of a tunnel.
+     *
+     * @return bandwidth utilization
+     */
+    double bandwidthUtilization();
+
+    /**
+     * Returns the packet loss rate of a tunnel.
+     *
+     * @return tunnel packet loss ratio
+     */
+    double packetLossRate();
+
+    /**
+     * Returns the end-to-end traffic flow delay of a tunnel.
+     *
+     * @return tunnel flow delay
+     */
+    Duration flowDelay();
+
+    /**
+     * Returns the alarms on a tunnel.
+     *
+     * @return tunnel alarms
+     */
+    List<String> alarms();
+}