diff --git a/core/api/src/main/java/org/onosproject/net/topology/DefaultGraphDescription.java b/core/api/src/main/java/org/onosproject/net/topology/DefaultGraphDescription.java
index d635d74..f1e20da 100644
--- a/core/api/src/main/java/org/onosproject/net/topology/DefaultGraphDescription.java
+++ b/core/api/src/main/java/org/onosproject/net/topology/DefaultGraphDescription.java
@@ -27,6 +27,7 @@
 
 import java.util.Map;
 
+import static com.google.common.base.Preconditions.checkArgument;
 import static org.slf4j.LoggerFactory.getLogger;
 
 /**
@@ -133,9 +134,7 @@
     private TopologyVertex vertexOf(ConnectPoint connectPoint) {
         DeviceId id = connectPoint.deviceId();
         TopologyVertex vertex = vertexesById.get(id);
-        if (vertex == null) {
-            throw new IllegalArgumentException("Vertex missing for " + id);
-        }
+        checkArgument(vertex != null, "Vertex missing for %s", id);
         return vertex;
     }
 
diff --git a/core/common/src/main/java/org/onosproject/common/DefaultTopology.java b/core/common/src/main/java/org/onosproject/common/DefaultTopology.java
index 51857c7..579f336 100644
--- a/core/common/src/main/java/org/onosproject/common/DefaultTopology.java
+++ b/core/common/src/main/java/org/onosproject/common/DefaultTopology.java
@@ -50,7 +50,9 @@
 import java.util.Set;
 
 import static com.google.common.base.MoreObjects.toStringHelper;
+import static com.google.common.base.Preconditions.checkArgument;
 import static org.onlab.graph.GraphPathSearch.ALL_PATHS;
+import static org.onlab.util.Tools.isNullOrEmpty;
 import static org.onosproject.core.CoreService.CORE_PROVIDER_ID;
 import static org.onosproject.net.Link.State.ACTIVE;
 import static org.onosproject.net.Link.State.INACTIVE;
@@ -228,15 +230,12 @@
 
         // Find the cluster to which the device belongs.
         TopologyCluster cluster = clustersByDevice().get(connectPoint.deviceId());
-        if (cluster == null) {
-            throw new IllegalArgumentException("No cluster found for device "
-                                                       + connectPoint.deviceId());
-        }
+        checkArgument(cluster != null, "No cluster found for device %s", connectPoint.deviceId());
 
         // If the broadcast set is null or empty, or if the point explicitly
-        // belongs to it, return true;
+        // belongs to it, return true.
         Set<ConnectPoint> points = broadcastSets.get().get(cluster.id());
-        return (points == null) || points.isEmpty() || points.contains(connectPoint);
+        return isNullOrEmpty(points) || points.contains(connectPoint);
     }
 
     /**
@@ -250,6 +249,16 @@
     }
 
     /**
+     * Returns the set of the cluster broadcast points.
+     *
+     * @param clusterId cluster identifier
+     * @return set of cluster broadcast points
+     */
+    public Set<ConnectPoint> broadcastPoints(ClusterId clusterId) {
+        return broadcastSets.get().get(clusterId);
+    }
+
+    /**
      * Returns the set of pre-computed shortest paths between source and
      * destination devices.
      *
diff --git a/core/net/src/main/java/org/onosproject/net/topology/impl/DefaultTopologyProvider.java b/core/net/src/main/java/org/onosproject/net/topology/impl/DefaultTopologyProvider.java
index e9ab196..20a5ad3 100644
--- a/core/net/src/main/java/org/onosproject/net/topology/impl/DefaultTopologyProvider.java
+++ b/core/net/src/main/java/org/onosproject/net/topology/impl/DefaultTopologyProvider.java
@@ -279,8 +279,7 @@
             try {
                 buildTopology(reasons);
             } catch (Exception e) {
-                log.warn("Unable to compute topology due to: {}", e.getMessage());
-                log.debug("Unable to compute topology", e);
+                log.warn("Unable to compute topology", e);
             }
         }
     }
diff --git a/core/store/dist/src/main/java/org/onosproject/store/topology/impl/DistributedTopologyStore.java b/core/store/dist/src/main/java/org/onosproject/store/topology/impl/DistributedTopologyStore.java
index 928603c..3a0f185 100644
--- a/core/store/dist/src/main/java/org/onosproject/store/topology/impl/DistributedTopologyStore.java
+++ b/core/store/dist/src/main/java/org/onosproject/store/topology/impl/DistributedTopologyStore.java
@@ -65,7 +65,7 @@
 
     private volatile DefaultTopology current =
             new DefaultTopology(ProviderId.NONE,
-                                new DefaultGraphDescription(0L, 0L,
+                                new DefaultGraphDescription(0L, System.currentTimeMillis(),
                                                             Collections.<Device>emptyList(),
                                                             Collections.<Link>emptyList()));
 
@@ -147,8 +147,7 @@
         }
 
         // Have the default topology construct self from the description data.
-        DefaultTopology newTopology =
-                new DefaultTopology(providerId, graphDescription);
+        DefaultTopology newTopology = new DefaultTopology(providerId, graphDescription);
 
         // Promote the new topology to current and return a ready-to-send event.
         synchronized (this) {