Device Anti-Entropy

- create Advertisement
- handler for Advertisement
- register handler, background thread to send advertisement

Change-Id: I99e8a7d68747970c34b3c25c6d0489769d251446
diff --git a/core/api/src/main/java/org/onlab/onos/net/device/DefaultPortDescription.java b/core/api/src/main/java/org/onlab/onos/net/device/DefaultPortDescription.java
index e1dcf9e..3967030 100644
--- a/core/api/src/main/java/org/onlab/onos/net/device/DefaultPortDescription.java
+++ b/core/api/src/main/java/org/onlab/onos/net/device/DefaultPortDescription.java
@@ -4,6 +4,8 @@
 import org.onlab.onos.net.PortNumber;
 import org.onlab.onos.net.SparseAnnotations;
 
+import com.google.common.base.MoreObjects;
+
 /**
  * Default implementation of immutable port description.
  */
@@ -48,6 +50,15 @@
         return isEnabled;
     }
 
+    @Override
+    public String toString() {
+        return MoreObjects.toStringHelper(getClass())
+                .add("number", number)
+                .add("isEnabled", isEnabled)
+                .add("annotations", annotations())
+                .toString();
+    }
+
     // default constructor for serialization
     private DefaultPortDescription() {
         this.number = null;