Added topology command-lines.
diff --git a/core/trivial/src/main/java/org/onlab/onos/net/trivial/topology/impl/DefaultTopology.java b/core/trivial/src/main/java/org/onlab/onos/net/trivial/topology/impl/DefaultTopology.java
index 86b88b3..ef87867 100644
--- a/core/trivial/src/main/java/org/onlab/onos/net/trivial/topology/impl/DefaultTopology.java
+++ b/core/trivial/src/main/java/org/onlab/onos/net/trivial/topology/impl/DefaultTopology.java
@@ -133,6 +133,17 @@
     }
 
     /**
+     * Returns the specified topology cluster.
+     *
+     * @param clusterId cluster identifier
+     * @return topology cluster
+     */
+    TopologyCluster getCluster(ClusterId clusterId) {
+        return clusters.get(clusterId);
+    }
+
+
+    /**
      * Returns the set of cluster devices.
      *
      * @param cluster topology cluster
diff --git a/core/trivial/src/main/java/org/onlab/onos/net/trivial/topology/impl/SimpleTopologyManager.java b/core/trivial/src/main/java/org/onlab/onos/net/trivial/topology/impl/SimpleTopologyManager.java
index 24bb256..6ad8f4b 100644
--- a/core/trivial/src/main/java/org/onlab/onos/net/trivial/topology/impl/SimpleTopologyManager.java
+++ b/core/trivial/src/main/java/org/onlab/onos/net/trivial/topology/impl/SimpleTopologyManager.java
@@ -11,9 +11,11 @@
 import org.onlab.onos.event.EventDeliveryService;
 import org.onlab.onos.net.ConnectPoint;
 import org.onlab.onos.net.DeviceId;
+import org.onlab.onos.net.Link;
 import org.onlab.onos.net.Path;
 import org.onlab.onos.net.provider.AbstractProviderRegistry;
 import org.onlab.onos.net.provider.AbstractProviderService;
+import org.onlab.onos.net.topology.ClusterId;
 import org.onlab.onos.net.topology.GraphDescription;
 import org.onlab.onos.net.topology.LinkWeight;
 import org.onlab.onos.net.topology.Topology;
@@ -44,6 +46,8 @@
 
     public static final String TOPOLOGY_NULL = "Topology cannot be null";
     private static final String DEVICE_ID_NULL = "Device ID cannot be null";
+    private static final String CLUSTER_ID_NULL = "Cluster ID cannot be null";
+    private static final String CLUSTER_NULL = "Topology cluster cannot be null";
     public static final String CONNECTION_POINT_NULL = "Connection point cannot be null";
 
     private final Logger log = getLogger(getClass());
@@ -96,6 +100,27 @@
     }
 
     @Override
+    public TopologyCluster getCluster(Topology topology, ClusterId clusterId) {
+        checkNotNull(topology, TOPOLOGY_NULL);
+        checkNotNull(topology, CLUSTER_ID_NULL);
+        return store.getCluster(defaultTopology(topology), clusterId);
+    }
+
+    @Override
+    public Set<DeviceId> getClusterDevices(Topology topology, TopologyCluster cluster) {
+        checkNotNull(topology, TOPOLOGY_NULL);
+        checkNotNull(topology, CLUSTER_NULL);
+        return store.getClusterDevices(defaultTopology(topology), cluster);
+    }
+
+    @Override
+    public Set<Link> getClusterLinks(Topology topology, TopologyCluster cluster) {
+        checkNotNull(topology, TOPOLOGY_NULL);
+        checkNotNull(topology, CLUSTER_NULL);
+        return store.getClusterLinks(defaultTopology(topology), cluster);
+    }
+
+    @Override
     public TopologyGraph getGraph(Topology topology) {
         checkNotNull(topology, TOPOLOGY_NULL);
         return store.getGraph(defaultTopology(topology));
diff --git a/core/trivial/src/main/java/org/onlab/onos/net/trivial/topology/impl/SimpleTopologyStore.java b/core/trivial/src/main/java/org/onlab/onos/net/trivial/topology/impl/SimpleTopologyStore.java
index b167dbc..f432ade 100644
--- a/core/trivial/src/main/java/org/onlab/onos/net/trivial/topology/impl/SimpleTopologyStore.java
+++ b/core/trivial/src/main/java/org/onlab/onos/net/trivial/topology/impl/SimpleTopologyStore.java
@@ -3,8 +3,10 @@
 import org.onlab.onos.event.Event;
 import org.onlab.onos.net.ConnectPoint;
 import org.onlab.onos.net.DeviceId;
+import org.onlab.onos.net.Link;
 import org.onlab.onos.net.Path;
 import org.onlab.onos.net.provider.ProviderId;
+import org.onlab.onos.net.topology.ClusterId;
 import org.onlab.onos.net.topology.GraphDescription;
 import org.onlab.onos.net.topology.LinkWeight;
 import org.onlab.onos.net.topology.Topology;
@@ -44,6 +46,16 @@
     }
 
     /**
+     * Returns the immutable graph view of the current topology.
+     *
+     * @param topology topology descriptor
+     * @return graph view
+     */
+    TopologyGraph getGraph(DefaultTopology topology) {
+        return topology.getGraph();
+    }
+
+    /**
      * Returns the set of topology SCC clusters.
      *
      * @param topology topology descriptor
@@ -54,13 +66,36 @@
     }
 
     /**
-     * Returns the immutable graph view of the current topology.
+     * Returns the cluster of the specified topology.
      *
-     * @param topology topology descriptor
-     * @return graph view
+     * @param topology  topology descriptor
+     * @param clusterId cluster identity
+     * @return topology cluster
      */
-    TopologyGraph getGraph(DefaultTopology topology) {
-        return topology.getGraph();
+    TopologyCluster getCluster(DefaultTopology topology, ClusterId clusterId) {
+        return topology.getCluster(clusterId);
+    }
+
+    /**
+     * Returns the cluster of the specified topology.
+     *
+     * @param topology  topology descriptor
+     * @param cluster topology cluster
+     * @return set of cluster links
+     */
+    Set<DeviceId> getClusterDevices(DefaultTopology topology, TopologyCluster cluster) {
+        return topology.getClusterDevices(cluster);
+    }
+
+    /**
+     * Returns the cluster of the specified topology.
+     *
+     * @param topology  topology descriptor
+     * @param cluster topology cluster
+     * @return set of cluster links
+     */
+    Set<Link> getClusterLinks(DefaultTopology topology, TopologyCluster cluster) {
+        return topology.getClusterLinks(cluster);
     }
 
     /**