diff --git a/alto-bwmonitor/impl/src/main/java/org/opendaylight/alto/ext/impl/BwFetchingService.java b/alto-bwmonitor/impl/src/main/java/org/opendaylight/alto/ext/impl/BwFetchingService.java
index 46e96ca..ba494e6 100644
--- a/alto-bwmonitor/impl/src/main/java/org/opendaylight/alto/ext/impl/BwFetchingService.java
+++ b/alto-bwmonitor/impl/src/main/java/org/opendaylight/alto/ext/impl/BwFetchingService.java
@@ -44,7 +44,8 @@ public class BwFetchingService implements DataTreeChangeListener<NodeConnector>
     /**
      * Parameter to calculate the speed (magic number?)
      */
-    private final Integer timeSpan = 3;
+    private final static Integer TIME_SPAN = 3;
+    private final static Long NANOSECOND_PER_SECOND = 1000000000L;
 
     /**
      * Contructor to get essential variables
@@ -56,7 +57,7 @@ public BwFetchingService(DataBroker dataBroker){
         LOG.info("BwFetchingService initialized");
     }
 
-    class Statistic{
+    class Statistic {
         /**
          * Timestamp -> Bytes
          */
@@ -68,7 +69,7 @@ class Statistic{
         Long capacity;
         Long availBw;
 
-        public Statistic(){
+        public Statistic() {
             rxHistory = new HashMap<>();
             txHistory = new HashMap<>();
             rxSpeed = 0L;
@@ -81,9 +82,10 @@ public Statistic(){
     Map<String, Statistic> statisticData = new HashMap<>();
 
     private void syncToDataBroker(String name, Statistic statistic) {
-        BwmonitorUtils.writeToSpeeds(name, statistic.rxSpeed, statistic.txSpeed, dataBroker);
-        LOG.debug("Bwmonitor speeds updated: rxSpeed={}, txSpeed={}",
-                statistic.rxSpeed, statistic.txSpeed);
+        BwmonitorUtils.writeToSpeeds(name, statistic.rxSpeed, statistic.txSpeed,
+                statistic.capacity, statistic.availBw, dataBroker);
+        LOG.debug("Bwmonitor speeds updated: rxSpeed={}, txSpeed={}, capacity={}, availBw={}",
+                statistic.rxSpeed, statistic.txSpeed, statistic.capacity, statistic.availBw);
     }
 
     private void registerPortListener() {
@@ -97,7 +99,6 @@ private void registerPortListener() {
 
     @Override
     public void onDataTreeChanged(@Nonnull Collection<DataTreeModification<NodeConnector>> changes) {
-        LOG.debug("Get Data Changed");
         exec.submit(() -> {
             for (DataTreeModification<NodeConnector> change: changes) {
                 DataObjectModification<NodeConnector> rootNode = change.getRootNode();
@@ -132,25 +133,34 @@ private void onFlowCapableNodeConnectorStatisticsDataUpdated(
         String id = identifier.firstKeyOf(NodeConnector.class).getId().getValue();
         if (statisticData.containsKey(id)) {
             statistic = statisticData.get(id);
+            LOG.debug("Get historical statistic of port {}: {}", id, statistic);
         } else {
             LOG.debug("Port is not subscribed for monitoring!");
             return;
         }
         if (updatedStatistic != null) {
+            LOG.debug("Reading new statistic of port {}", id);
             Bytes bytes = updatedStatistic.getFlowCapableNodeConnectorStatistics().getBytes();
+            LOG.debug("Done to read port statistic");
             if (bytes != null) {
+                LOG.debug("Processing new statistic");
                 Long timestamp = updatedStatistic.getFlowCapableNodeConnectorStatistics()
-                    .getDuration().getSecond().getValue();
+                    .getDuration().getSecond().getValue() * NANOSECOND_PER_SECOND + updatedStatistic.getFlowCapableNodeConnectorStatistics()
+                    .getDuration().getNanosecond().getValue();
                 statistic.rxHistory.put(timestamp, bytes.getReceived().longValue());
                 statistic.txHistory.put(timestamp, bytes.getTransmitted().longValue());
                 statistic.rxSpeed = computeStatisticFromHistory(statistic.rxHistory, timestamp);
                 statistic.txSpeed = computeStatisticFromHistory(statistic.txHistory, timestamp);
+                LOG.debug("Compute new rate of port {}: rx={}, tx={}", id, statistic.rxSpeed, statistic.txSpeed);
             }
         }
+        LOG.debug("Done to process new statistic");
         FlowCapableNodeConnector updatedFlowPort = updatedPort
             .getAugmentation(FlowCapableNodeConnector.class);
         if (updatedFlowPort != null) {
+            LOG.debug("Reading capacity of port {}", id);
             statistic.capacity = updatedFlowPort.getCurrentSpeed();
+            LOG.debug("Done to read capacity");
             statistic.availBw = statistic.capacity - statistic.txSpeed / 128;
         }
         if (statistic != null) {
@@ -160,7 +170,7 @@ private void onFlowCapableNodeConnectorStatisticsDataUpdated(
 
     private void cleanStatisticHistory(Map<Long, Long> history, Long timestamp, boolean inTimeSpan) {
         if (inTimeSpan) {
-            history.entrySet().removeIf(e -> e.getKey() < (timestamp - timeSpan));
+            history.entrySet().removeIf(e -> e.getKey() < (timestamp - TIME_SPAN));
         } else {
             Long maxTime = Long.valueOf(0);
             for (Map.Entry<Long, Long> item : history.entrySet()) {
@@ -176,13 +186,19 @@ private void cleanStatisticHistory(Map<Long, Long> history, Long timestamp, bool
         }
     }
 
+    /**
+     * Compute ewma of port statistic.
+     * @param history the historical rate statistic of this port (bytes)
+     * @param timestamp the duration time since start statistic (nanoseconds)
+     * @return the ewma of port statistic
+     */
     private Long computeStatisticFromHistory(Map<Long, Long> history, Long timestamp) {
         /**
          * current speed = (average speed in timeSpan) * 0.8 + (speed from last history record) * 0.2
          */
         boolean inTimeSpan = false;
         for (Map.Entry<Long, Long> item : history.entrySet()) {
-            if (!item.getKey().equals(timestamp) && item.getKey() > timestamp - timeSpan) {
+            if (!item.getKey().equals(timestamp) && item.getKey() > timestamp - TIME_SPAN) {
                 inTimeSpan = true;
                 break;
             }
@@ -196,9 +212,9 @@ private Long computeStatisticFromHistory(Map<Long, Long> history, Long timestamp
             if (item.getKey() != timestamp && item.getKey() > maxTime)
                 maxTime = item.getKey();
         }
-        Long speedFromLastRecord = (history.get(maxTime) - history.get(timestamp)) / (timestamp - maxTime);
+        Long speedFromLastRecord = (history.get(maxTime) - history.get(timestamp)) * NANOSECOND_PER_SECOND / (timestamp - maxTime);
         if (inTimeSpan) {
-            Long speedFromTimeSpan = (history.get(minTime) - history.get(timestamp)) / (timestamp - minTime);
+            Long speedFromTimeSpan = (history.get(minTime) - history.get(timestamp)) * NANOSECOND_PER_SECOND / (timestamp - minTime);
             return (long)(speedFromTimeSpan * 0.8 + speedFromLastRecord * 0.2);
         } else {
             return speedFromLastRecord;
diff --git a/alto-bwmonitor/impl/src/main/java/org/opendaylight/alto/ext/impl/BwmonitorUtils.java b/alto-bwmonitor/impl/src/main/java/org/opendaylight/alto/ext/impl/BwmonitorUtils.java
index 1fe21da..30cd7bf 100644
--- a/alto-bwmonitor/impl/src/main/java/org/opendaylight/alto/ext/impl/BwmonitorUtils.java
+++ b/alto-bwmonitor/impl/src/main/java/org/opendaylight/alto/ext/impl/BwmonitorUtils.java
@@ -35,12 +35,15 @@ private static InstanceIdentifier<Port> toInstanceIdentifier(String nodeId) {
         return iid;
     }
 
-    public static boolean writeToSpeeds(String portId, Long rxSpeed, Long txSpeed, DataBroker db) {
+    public static boolean writeToSpeeds(String portId, Long rxSpeed, Long txSpeed,
+            Long capacity, Long availBw, DataBroker db) {
         WriteTransaction transaction = db.newWriteOnlyTransaction();
         InstanceIdentifier<Port> iid = BwmonitorUtils.toInstanceIdentifier(portId);
         Port node = new PortBuilder().setPortId(portId)
                 .setRxSpeed(BigInteger.valueOf(rxSpeed))
                 .setTxSpeed(BigInteger.valueOf(txSpeed))
+                .setCapacity(capacity)
+                .setAvailBw(availBw)
                 .build();
         transaction.put(LogicalDatastoreType.OPERATIONAL, iid, node);
         CheckedFuture<Void, TransactionCommitFailedException> future = transaction.submit();