diff --git a/core/api/src/main/java/org/onosproject/ui/UiExtension.java b/core/api/src/main/java/org/onosproject/ui/UiExtension.java
index 17201cb..9edcba9a 100644
--- a/core/api/src/main/java/org/onosproject/ui/UiExtension.java
+++ b/core/api/src/main/java/org/onosproject/ui/UiExtension.java
@@ -47,6 +47,7 @@
     private final List<UiView> viewList;
     private final UiMessageHandlerFactory messageHandlerFactory;
     private final UiTopoOverlayFactory topoOverlayFactory;
+    private final UiTopo2OverlayFactory topo2OverlayFactory;
     private final UiTopoMapFactory topoMapFactory;
 
     private boolean isValid = true;
@@ -55,12 +56,14 @@
     private UiExtension(ClassLoader cl, String path, List<UiView> views,
                         UiMessageHandlerFactory mhFactory,
                         UiTopoOverlayFactory toFactory,
+                        UiTopo2OverlayFactory to2Factory,
                         UiTopoMapFactory tmFactory) {
         classLoader = cl;
         resourcePath = path;
         viewList = views;
         messageHandlerFactory = mhFactory;
         topoOverlayFactory = toFactory;
+        topo2OverlayFactory = to2Factory;
         topoMapFactory = tmFactory;
     }
 
@@ -122,6 +125,15 @@
     }
 
     /**
+     * Returns the topology-2 overlay factory, if one was defined.
+     *
+     * @return topology-2 overlay factory
+     */
+    public UiTopo2OverlayFactory topo2OverlayFactory() {
+        return topo2OverlayFactory;
+    }
+
+    /**
      * Returns the topology map factory, if one was defined.
      *
      * @return topology map factory
@@ -152,6 +164,7 @@
         private List<UiView> viewList = new ArrayList<>();
         private UiMessageHandlerFactory messageHandlerFactory = null;
         private UiTopoOverlayFactory topoOverlayFactory = null;
+        private UiTopo2OverlayFactory topo2OverlayFactory = null;
         private UiTopoMapFactory topoMapFactory = null;
 
         /**
@@ -205,6 +218,17 @@
         }
 
         /**
+         * Sets the topology-2 overlay factory for this extension.
+         *
+         * @param to2Factory topology-2 overlay factory
+         * @return self, for chaining
+         */
+        public Builder topo2OverlayFactory(UiTopo2OverlayFactory to2Factory) {
+            topo2OverlayFactory = to2Factory;
+            return this;
+        }
+
+        /**
          * Sets the topology map factory for this extension.
          *
          * @param tmFactory topology map factory
@@ -222,8 +246,8 @@
          */
         public UiExtension build() {
             return new UiExtension(classLoader, resourcePath, viewList,
-                                    messageHandlerFactory, topoOverlayFactory,
-                                    topoMapFactory);
+                                   messageHandlerFactory, topoOverlayFactory,
+                                   topo2OverlayFactory, topoMapFactory);
         }
     }
 }
diff --git a/core/api/src/main/java/org/onosproject/ui/UiTopo2Overlay.java b/core/api/src/main/java/org/onosproject/ui/UiTopo2Overlay.java
new file mode 100644
index 0000000..940080e
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/ui/UiTopo2Overlay.java
@@ -0,0 +1,132 @@
+/*
+ * Copyright 2017-present 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.ui;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Represents a user interface topology-2 view overlay.
+ * <p>
+ * This base class does little more than provide a logger, an identifier,
+ * name, and glyph ID.
+ * Subclasses will probably want to override some or all of the base methods
+ * to do useful things during the life-cycle of the (topo-2) overlay.
+ */
+public class UiTopo2Overlay {
+
+    private static final String DEFAULT_GLYPH_ID = "m_topo";
+
+    /**
+     * Logger for this overlay.
+     */
+    protected final Logger log = LoggerFactory.getLogger(getClass());
+
+    private final String id;
+    private final String name;
+
+    private boolean isActive = false;
+
+    /**
+     * Creates a new user interface topology view overlay descriptor, with
+     * the given identifier and (human readable) name.
+     *
+     * @param id overlay identifier
+     * @param name overlay name
+     */
+    public UiTopo2Overlay(String id, String name) {
+        this.id = id;
+        this.name = name;
+    }
+
+    /**
+     * Returns the identifier for this overlay.
+     *
+     * @return the identifier
+     */
+    public String id() {
+        return id;
+    }
+
+    /**
+     * Returns the name for this overlay.
+     *
+     * @return the name
+     */
+    public String name() {
+        return name;
+    }
+
+    /**
+     * Returns the glyph identifier to use in the toolbar.
+     * This implementation returns a default value. Subclasses may override
+     * this to provide the identity of a custom glyph.
+     *
+     * @return glyph ID
+     */
+    public String glyphId() {
+        return DEFAULT_GLYPH_ID;
+    }
+
+    /**
+     * Callback invoked to initialize this overlay, soon after creation.
+     * This default implementation does nothing.
+     */
+    public void init() {
+    }
+
+    /**
+     * Callback invoked when this overlay is activated.
+     */
+    public void activate() {
+        isActive = true;
+    }
+
+    /**
+     * Callback invoked when this overlay is deactivated.
+     */
+    public void deactivate() {
+        isActive = false;
+    }
+
+    /**
+     * Returns true if this overlay is currently active.
+     *
+     * @return true if overlay active
+     */
+    public boolean isActive() {
+        return isActive;
+    }
+
+    /**
+     * Callback invoked to destroy this instance by cleaning up any
+     * internal state ready for garbage collection.
+     * This default implementation holds no state and does nothing.
+     */
+    public void destroy() {
+    }
+
+    /**
+     * Callback invoked when the topology highlighting should be updated.
+     * It is the implementation's responsibility to update the Model
+     * Highlighter state. This implementation does nothing.
+     */
+    public void highlightingCallback(/* ref to highlight model ? */) {
+
+    }
+}
diff --git a/core/api/src/main/java/org/onosproject/ui/UiTopo2OverlayFactory.java b/core/api/src/main/java/org/onosproject/ui/UiTopo2OverlayFactory.java
new file mode 100644
index 0000000..d6718fa
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/ui/UiTopo2OverlayFactory.java
@@ -0,0 +1,34 @@
+/*
+ * Copyright 2017-present 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.ui;
+
+import java.util.Collection;
+
+/**
+ * Abstraction of an entity capable of producing one or more topology-2
+ * overlay handlers specific to a given user interface connection.
+ */
+public interface UiTopo2OverlayFactory {
+
+    /**
+     * Produces a collection of new overlay handlers for topology-2 view.
+     *
+     * @return collection of new overlay handlers
+     */
+    Collection<UiTopo2Overlay> newOverlays();
+}