diff --git a/core/common/src/main/java/org/onosproject/common/DefaultTopology.java b/core/common/src/main/java/org/onosproject/common/DefaultTopology.java
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+/*
+ * Copyright 2014-2015 Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.common;
+
+import com.google.common.base.Supplier;
+import com.google.common.base.Suppliers;
+import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.ImmutableSetMultimap;
+import com.google.common.collect.ImmutableSetMultimap.Builder;
+import org.onlab.graph.DijkstraGraphSearch;
+import org.onlab.graph.GraphPathSearch;
+import org.onlab.graph.GraphPathSearch.Result;
+import org.onlab.graph.TarjanGraphSearch;
+import org.onlab.graph.TarjanGraphSearch.SCCResult;
+import org.onosproject.net.AbstractModel;
+import org.onosproject.net.ConnectPoint;
+import org.onosproject.net.DefaultPath;
+import org.onosproject.net.DeviceId;
+import org.onosproject.net.Link;
+import org.onosproject.net.Path;
+import org.onosproject.net.provider.ProviderId;
+import org.onosproject.net.topology.ClusterId;
+import org.onosproject.net.topology.DefaultTopologyCluster;
+import org.onosproject.net.topology.DefaultTopologyVertex;
+import org.onosproject.net.topology.GraphDescription;
+import org.onosproject.net.topology.LinkWeight;
+import org.onosproject.net.topology.Topology;
+import org.onosproject.net.topology.TopologyCluster;
+import org.onosproject.net.topology.TopologyEdge;
+import org.onosproject.net.topology.TopologyGraph;
+import org.onosproject.net.topology.TopologyVertex;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+import static com.google.common.base.MoreObjects.toStringHelper;
+import static org.onlab.graph.GraphPathSearch.ALL_PATHS;
+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;
+import static org.onosproject.net.Link.Type.INDIRECT;
+
+/**
+ * Default implementation of the topology descriptor. This carries the backing
+ * topology data.
+ */
+public class DefaultTopology extends AbstractModel implements Topology {
+
+    private static final DijkstraGraphSearch<TopologyVertex, TopologyEdge> DIJKSTRA = new DijkstraGraphSearch<>();
+    private static final TarjanGraphSearch<TopologyVertex, TopologyEdge> TARJAN = new TarjanGraphSearch<>();
+
+    private final long time;
+    private final long creationTime;
+    private final long computeCost;
+    private final TopologyGraph graph;
+
+    private final LinkWeight weight;
+    private final Supplier<SCCResult<TopologyVertex, TopologyEdge>> clusterResults;
+    private final Supplier<ImmutableMap<ClusterId, TopologyCluster>> clusters;
+    private final Supplier<ImmutableSet<ConnectPoint>> infrastructurePoints;
+    private final Supplier<ImmutableSetMultimap<ClusterId, ConnectPoint>> broadcastSets;
+
+    private final Supplier<ClusterIndexes> clusterIndexes;
+
+    /**
+     * Creates a topology descriptor attributed to the specified provider.
+     *
+     * @param providerId  identity of the provider
+     * @param description data describing the new topology
+     */
+    public DefaultTopology(ProviderId providerId, GraphDescription description) {
+        super(providerId);
+        this.time = description.timestamp();
+        this.creationTime = description.creationTime();
+
+        // Build the graph
+        this.graph = new DefaultTopologyGraph(description.vertexes(),
+                                              description.edges());
+
+        this.clusterResults = Suppliers.memoize(() -> searchForClusters());
+        this.clusters = Suppliers.memoize(() -> buildTopologyClusters());
+
+        this.clusterIndexes = Suppliers.memoize(() -> buildIndexes());
+
+        this.weight = new HopCountLinkWeight(graph.getVertexes().size());
+        this.broadcastSets = Suppliers.memoize(() -> buildBroadcastSets());
+        this.infrastructurePoints = Suppliers.memoize(() -> findInfrastructurePoints());
+        this.computeCost = Math.max(0, System.nanoTime() - time);
+    }
+
+    @Override
+    public long time() {
+        return time;
+    }
+
+    @Override
+    public long creationTime() {
+        return creationTime;
+    }
+
+    @Override
+    public long computeCost() {
+        return computeCost;
+    }
+
+    @Override
+    public int clusterCount() {
+        return clusters.get().size();
+    }
+
+    @Override
+    public int deviceCount() {
+        return graph.getVertexes().size();
+    }
+
+    @Override
+    public int linkCount() {
+        return graph.getEdges().size();
+    }
+
+    private ImmutableMap<DeviceId, TopologyCluster> clustersByDevice() {
+        return clusterIndexes.get().clustersByDevice;
+    }
+
+    private ImmutableSetMultimap<TopologyCluster, DeviceId> devicesByCluster() {
+        return clusterIndexes.get().devicesByCluster;
+    }
+
+    private ImmutableSetMultimap<TopologyCluster, Link> linksByCluster() {
+        return clusterIndexes.get().linksByCluster;
+    }
+
+    /**
+     * Returns the backing topology graph.
+     *
+     * @return topology graph
+     */
+    public TopologyGraph getGraph() {
+        return graph;
+    }
+
+    /**
+     * Returns the set of topology clusters.
+     *
+     * @return set of clusters
+     */
+    public Set<TopologyCluster> getClusters() {
+        return ImmutableSet.copyOf(clusters.get().values());
+    }
+
+    /**
+     * Returns the specified topology cluster.
+     *
+     * @param clusterId cluster identifier
+     * @return topology cluster
+     */
+    public TopologyCluster getCluster(ClusterId clusterId) {
+        return clusters.get().get(clusterId);
+    }
+
+    /**
+     * Returns the topology cluster that contains the given device.
+     *
+     * @param deviceId device identifier
+     * @return topology cluster
+     */
+    public TopologyCluster getCluster(DeviceId deviceId) {
+        return clustersByDevice().get(deviceId);
+    }
+
+    /**
+     * Returns the set of cluster devices.
+     *
+     * @param cluster topology cluster
+     * @return cluster devices
+     */
+    public Set<DeviceId> getClusterDevices(TopologyCluster cluster) {
+        return devicesByCluster().get(cluster);
+    }
+
+    /**
+     * Returns the set of cluster links.
+     *
+     * @param cluster topology cluster
+     * @return cluster links
+     */
+    public Set<Link> getClusterLinks(TopologyCluster cluster) {
+        return linksByCluster().get(cluster);
+    }
+
+    /**
+     * Indicates whether the given point is an infrastructure link end-point.
+     *
+     * @param connectPoint connection point
+     * @return true if infrastructure
+     */
+    public boolean isInfrastructure(ConnectPoint connectPoint) {
+        return infrastructurePoints.get().contains(connectPoint);
+    }
+
+    /**
+     * Indicates whether the given point is part of a broadcast set.
+     *
+     * @param connectPoint connection point
+     * @return true if in broadcast set
+     */
+    public boolean isBroadcastPoint(ConnectPoint connectPoint) {
+        // Any non-infrastructure, i.e. edge points are assumed to be OK.
+        if (!isInfrastructure(connectPoint)) {
+            return true;
+        }
+
+        // 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());
+        }
+
+        // If the broadcast set is null or empty, or if the point explicitly
+        // belongs to it, return true;
+        Set<ConnectPoint> points = broadcastSets.get().get(cluster.id());
+        return (points == null) || points.isEmpty() || points.contains(connectPoint);
+    }
+
+    /**
+     * Returns the size of the cluster broadcast set.
+     *
+     * @param clusterId cluster identifier
+     * @return size of the cluster broadcast set
+     */
+    public int broadcastSetSize(ClusterId clusterId) {
+        return broadcastSets.get().get(clusterId).size();
+    }
+
+    /**
+     * Returns the set of pre-computed shortest paths between source and
+     * destination devices.
+     *
+     * @param src source device
+     * @param dst destination device
+     * @return set of shortest paths
+     */
+    public Set<Path> getPaths(DeviceId src, DeviceId dst) {
+        return getPaths(src, dst, null);
+    }
+
+    /**
+     * Computes on-demand the set of shortest paths between source and
+     * destination devices.
+     *
+     * @param src    source device
+     * @param dst    destination device
+     * @param weight link weight function
+     * @return set of shortest paths
+     */
+    public Set<Path> getPaths(DeviceId src, DeviceId dst, LinkWeight weight) {
+        final DefaultTopologyVertex srcV = new DefaultTopologyVertex(src);
+        final DefaultTopologyVertex dstV = new DefaultTopologyVertex(dst);
+        Set<TopologyVertex> vertices = graph.getVertexes();
+        if (!vertices.contains(srcV) || !vertices.contains(dstV)) {
+            // src or dst not part of the current graph
+            return ImmutableSet.of();
+        }
+
+        GraphPathSearch.Result<TopologyVertex, TopologyEdge> result =
+                DIJKSTRA.search(graph, srcV, dstV, weight, ALL_PATHS);
+        ImmutableSet.Builder<Path> builder = ImmutableSet.builder();
+        for (org.onlab.graph.Path<TopologyVertex, TopologyEdge> path : result.paths()) {
+            builder.add(networkPath(path));
+        }
+        return builder.build();
+    }
+
+    // Converts graph path to a network path with the same cost.
+    private Path networkPath(org.onlab.graph.Path<TopologyVertex, TopologyEdge> path) {
+        List<Link> links = new ArrayList<>();
+        for (TopologyEdge edge : path.edges()) {
+            links.add(edge.link());
+        }
+        return new DefaultPath(CORE_PROVIDER_ID, links, path.cost());
+    }
+
+    // Searches for SCC clusters in the network topology graph using Tarjan
+    // algorithm.
+    private SCCResult<TopologyVertex, TopologyEdge> searchForClusters() {
+        return TARJAN.search(graph, new NoIndirectLinksWeight());
+    }
+
+    // Builds the topology clusters and returns the id-cluster bindings.
+    private ImmutableMap<ClusterId, TopologyCluster> buildTopologyClusters() {
+        ImmutableMap.Builder<ClusterId, TopologyCluster> clusterBuilder = ImmutableMap.builder();
+        SCCResult<TopologyVertex, TopologyEdge> results = clusterResults.get();
+        // Extract both vertexes and edges from the results; the lists form
+        // pairs along the same index.
+        List<Set<TopologyVertex>> clusterVertexes = results.clusterVertexes();
+        List<Set<TopologyEdge>> clusterEdges = results.clusterEdges();
+
+        // Scan over the lists and create a cluster from the results.
+        for (int i = 0, n = results.clusterCount(); i < n; i++) {
+            Set<TopologyVertex> vertexSet = clusterVertexes.get(i);
+            Set<TopologyEdge> edgeSet = clusterEdges.get(i);
+
+            ClusterId cid = ClusterId.clusterId(i);
+            DefaultTopologyCluster cluster = new DefaultTopologyCluster(cid,
+                                                                        vertexSet.size(),
+                                                                        edgeSet.size(),
+                                                                        findRoot(vertexSet));
+            clusterBuilder.put(cid, cluster);
+        }
+        return clusterBuilder.build();
+    }
+
+    // Finds the vertex whose device id is the lexicographical minimum in the
+    // specified set.
+    private TopologyVertex findRoot(Set<TopologyVertex> vertexSet) {
+        TopologyVertex minVertex = null;
+        for (TopologyVertex vertex : vertexSet) {
+            if ((minVertex == null) || (minVertex.deviceId()
+                    .toString().compareTo(minVertex.deviceId().toString()) < 0)) {
+                minVertex = vertex;
+            }
+        }
+        return minVertex;
+    }
+
+    // Processes a map of broadcast sets for each cluster.
+    private ImmutableSetMultimap<ClusterId, ConnectPoint> buildBroadcastSets() {
+        Builder<ClusterId, ConnectPoint> builder = ImmutableSetMultimap
+                .builder();
+        for (TopologyCluster cluster : clusters.get().values()) {
+            addClusterBroadcastSet(cluster, builder);
+        }
+        return builder.build();
+    }
+
+    // Finds all broadcast points for the cluster. These are those connection
+    // points which lie along the shortest paths between the cluster root and
+    // all other devices within the cluster.
+    private void addClusterBroadcastSet(TopologyCluster cluster, Builder<ClusterId, ConnectPoint> builder) {
+        // Use the graph root search results to build the broadcast set.
+        Result<TopologyVertex, TopologyEdge> result = DIJKSTRA.search(graph, cluster.root(), null, weight, 1);
+        for (Map.Entry<TopologyVertex, Set<TopologyEdge>> entry : result.parents().entrySet()) {
+            TopologyVertex vertex = entry.getKey();
+
+            // Ignore any parents that lead outside the cluster.
+            if (clustersByDevice().get(vertex.deviceId()) != cluster) {
+                continue;
+            }
+
+            // Ignore any back-link sets that are empty.
+            Set<TopologyEdge> parents = entry.getValue();
+            if (parents.isEmpty()) {
+                continue;
+            }
+
+            // Use the first back-link source and destinations to add to the
+            // broadcast set.
+            Link link = parents.iterator().next().link();
+            builder.put(cluster.id(), link.src());
+            builder.put(cluster.id(), link.dst());
+        }
+    }
+
+    // Collects and returns an set of all infrastructure link end-points.
+    private ImmutableSet<ConnectPoint> findInfrastructurePoints() {
+        ImmutableSet.Builder<ConnectPoint> builder = ImmutableSet.builder();
+        for (TopologyEdge edge : graph.getEdges()) {
+            builder.add(edge.link().src());
+            builder.add(edge.link().dst());
+        }
+        return builder.build();
+    }
+
+    // Builds cluster-devices, cluster-links and device-cluster indexes.
+    private ClusterIndexes buildIndexes() {
+        // Prepare the index builders
+        ImmutableMap.Builder<DeviceId, TopologyCluster> clusterBuilder =
+                ImmutableMap.builder();
+        ImmutableSetMultimap.Builder<TopologyCluster, DeviceId> devicesBuilder =
+                ImmutableSetMultimap.builder();
+        ImmutableSetMultimap.Builder<TopologyCluster, Link> linksBuilder =
+                ImmutableSetMultimap.builder();
+
+        // Now scan through all the clusters
+        for (TopologyCluster cluster : clusters.get().values()) {
+            int i = cluster.id().index();
+
+            // Scan through all the cluster vertexes.
+            for (TopologyVertex vertex : clusterResults.get().clusterVertexes().get(i)) {
+                devicesBuilder.put(cluster, vertex.deviceId());
+                clusterBuilder.put(vertex.deviceId(), cluster);
+            }
+
+            // Scan through all the cluster edges.
+            for (TopologyEdge edge : clusterResults.get().clusterEdges().get(i)) {
+                linksBuilder.put(cluster, edge.link());
+            }
+        }
+
+        // Finalize all indexes.
+        return new ClusterIndexes(clusterBuilder.build(),
+                                  devicesBuilder.build(),
+                                  linksBuilder.build());
+    }
+
+    // Link weight for measuring link cost as hop count with indirect links
+    // being as expensive as traversing the entire graph to assume the worst.
+    private static class HopCountLinkWeight implements LinkWeight {
+        private final int indirectLinkCost;
+
+        HopCountLinkWeight(int indirectLinkCost) {
+            this.indirectLinkCost = indirectLinkCost;
+        }
+
+        @Override
+        public double weight(TopologyEdge edge) {
+            // To force preference to use direct paths first, make indirect
+            // links as expensive as the linear vertex traversal.
+            return edge.link().state() ==
+                    ACTIVE ? (edge.link().type() ==
+                    INDIRECT ? indirectLinkCost : 1) : -1;
+        }
+    }
+
+    // Link weight for preventing traversal over indirect links.
+    private static class NoIndirectLinksWeight implements LinkWeight {
+        @Override
+        public double weight(TopologyEdge edge) {
+            return (edge.link().state() == INACTIVE)
+                    || (edge.link().type() == INDIRECT) ? -1 : 1;
+        }
+    }
+
+    static final class ClusterIndexes {
+        final ImmutableMap<DeviceId, TopologyCluster> clustersByDevice;
+        final ImmutableSetMultimap<TopologyCluster, DeviceId> devicesByCluster;
+        final ImmutableSetMultimap<TopologyCluster, Link> linksByCluster;
+
+        public ClusterIndexes(ImmutableMap<DeviceId, TopologyCluster> clustersByDevice,
+                              ImmutableSetMultimap<TopologyCluster, DeviceId> devicesByCluster,
+                              ImmutableSetMultimap<TopologyCluster, Link> linksByCluster) {
+            this.clustersByDevice = clustersByDevice;
+            this.devicesByCluster = devicesByCluster;
+            this.linksByCluster = linksByCluster;
+        }
+    }
+
+    @Override
+    public String toString() {
+        return toStringHelper(this)
+                .add("time", time)
+                .add("creationTime", creationTime)
+                .add("computeCost", computeCost)
+                .add("clusters", clusterCount())
+                .add("devices", deviceCount())
+                .add("links", linkCount()).toString();
+    }
+}