[ONOS-2233] Implement of Tunnel monitoring, measurement and observation
1. add a tunnel statistics interface.
2. add a pcep tunnel statistics interface.
3. add a tunnelStatsCollector to poll statistic request ,The polling interval can be configurable.
4. extend the pcepTunnelProvider to handle tunnel statistic message

Change-Id: I1187d586a1833ca4bee55529a65cd61eff0e612d
diff --git a/incubator/api/src/main/java/org/onosproject/incubator/net/tunnel/DefaultTunnelStatistics.java b/incubator/api/src/main/java/org/onosproject/incubator/net/tunnel/DefaultTunnelStatistics.java
new file mode 100644
index 0000000..6358ca9
--- /dev/null
+++ b/incubator/api/src/main/java/org/onosproject/incubator/net/tunnel/DefaultTunnelStatistics.java
@@ -0,0 +1,168 @@
+/*
+ *
+ *  * 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;
+
+/**
+ * Default implementation of immutable tunnel statistics.
+ */
+public final class DefaultTunnelStatistics implements TunnelStatistics {
+    private final TunnelId tunnelId;
+    private final double bwUtilization;
+    private final double packetLossRatio;
+    private final Duration flowDelay;
+    private final List<String> alarms;
+
+    private DefaultTunnelStatistics(TunnelId tunnelId,
+                                    double bwUtilization,
+                                    double packetLossRatio,
+                                    Duration flowDelay,
+                                    List<String> alarms) {
+        this.tunnelId = tunnelId;
+        this.bwUtilization = bwUtilization;
+        this.packetLossRatio = packetLossRatio;
+        this.flowDelay = flowDelay;
+        this.alarms = alarms;
+    }
+
+    private DefaultTunnelStatistics() {
+        this.tunnelId = null;
+        this.bwUtilization = 0;
+        this.packetLossRatio = 0;
+        this.flowDelay = null;
+        this.alarms = null;
+    }
+
+
+    @Override
+    public TunnelId id() {
+        return this.tunnelId;
+    }
+
+    @Override
+    public double bandwidthUtilization() {
+        return this.bwUtilization;
+    }
+
+    @Override
+    public double packetLossRate() {
+        return this.packetLossRatio;
+    }
+
+    @Override
+    public Duration flowDelay() {
+        return this.flowDelay;
+    }
+
+
+    @Override
+    public List<String> alarms() {
+        return this.alarms;
+    }
+
+    /**
+     * Builder for tunnelStatistics.
+     */
+    public static final class Builder {
+        TunnelId tunnelId;
+        double bwUtilization;
+        double packetLossRatio;
+        Duration flowDelay;
+        List<String> alarms;
+
+        public Builder() {
+
+        }
+
+        /**
+         * Set tunnel id.
+         *
+         * @param tunnelId tunnel id
+         * @return builder object
+         */
+        public Builder setTunnelId(TunnelId tunnelId) {
+            this.tunnelId = tunnelId;
+
+            return this;
+        }
+
+        /**
+         * set bandwidth utilization.
+         *
+         * @param bwUtilization bandwidth utilization
+         * @return builder object
+         */
+        public Builder setBwUtilization(double bwUtilization) {
+            this.bwUtilization = bwUtilization;
+
+            return this;
+        }
+
+        /**
+         * Set packet loss ratio.
+         *
+         * @param packetLossRatio packet loss ratio
+         * @return builder object
+         */
+        public Builder setPacketLossRatio(double packetLossRatio) {
+            this.packetLossRatio = packetLossRatio;
+
+            return this;
+        }
+
+        /**
+         * Set flow delay.
+         *
+         * @param flowDelay flow delay
+         * @return builder object
+         */
+        public Builder setFlowDelay(Duration flowDelay) {
+            this.flowDelay = flowDelay;
+
+            return this;
+        }
+
+        /**
+         * Set alarms.
+         *
+         * @param alarms alarms of a tunnel
+         * @return builder object
+         */
+        public Builder setAlarms(List<String> alarms) {
+            this.alarms = alarms;
+
+            return this;
+        }
+
+        /**
+         * Creates a TunnelStatistics object.
+         *
+         * @return DefaultTunnelStatistics
+         */
+        public DefaultTunnelStatistics build() {
+            return new DefaultTunnelStatistics(tunnelId,
+                                               bwUtilization,
+                                               packetLossRatio,
+                                               flowDelay,
+                                               alarms);
+        }
+    }
+}