distributed link fixes

Change-Id: Iefede001a76834599a5629d843a4325283e42711
diff --git a/core/api/src/main/java/org/onlab/onos/net/link/DefaultLinkDescription.java b/core/api/src/main/java/org/onlab/onos/net/link/DefaultLinkDescription.java
index 65d8d6d..037b796 100644
--- a/core/api/src/main/java/org/onlab/onos/net/link/DefaultLinkDescription.java
+++ b/core/api/src/main/java/org/onlab/onos/net/link/DefaultLinkDescription.java
@@ -1,5 +1,6 @@
 package org.onlab.onos.net.link;
 
+import com.google.common.base.MoreObjects;
 import org.onlab.onos.net.AbstractDescription;
 import org.onlab.onos.net.ConnectPoint;
 import org.onlab.onos.net.Link;
@@ -46,4 +47,11 @@
         return type;
     }
 
+    @Override
+    public String toString() {
+        return MoreObjects.toStringHelper("Link").add("src", src())
+                                .add("dst", dst())
+                                .add("type", type()).toString();
+    }
+
 }