diff --git a/providers/null/src/main/java/org/onosproject/provider/nil/CustomTopologySimulator.java b/providers/null/src/main/java/org/onosproject/provider/nil/CustomTopologySimulator.java
new file mode 100644
index 0000000..016b187
--- /dev/null
+++ b/providers/null/src/main/java/org/onosproject/provider/nil/CustomTopologySimulator.java
@@ -0,0 +1,94 @@
+/*
+ * Copyright 2016 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.provider.nil;
+
+import com.google.common.collect.Maps;
+import org.onlab.packet.MacAddress;
+import org.onlab.packet.VlanId;
+import org.onosproject.net.Device;
+import org.onosproject.net.DeviceId;
+import org.onosproject.net.HostId;
+
+import java.util.Map;
+
+import static org.onlab.util.Tools.toHex;
+import static org.onosproject.provider.nil.NullProviders.SCHEME;
+
+/**
+ * Custom topology defined by a concise language.
+ */
+public class CustomTopologySimulator extends TopologySimulator {
+
+    private int nextDeviceId = 0;
+    private int nextHostId = 0;
+
+    private Map<String, DeviceId> nameToId = Maps.newConcurrentMap();
+
+    /**
+     * Returns the next device id.
+     *
+     * @return the next device id
+     */
+    public DeviceId nextDeviceId() {
+        return DeviceId.deviceId(SCHEME + ":" + toHex(++nextDeviceId));
+    }
+
+    /**
+     * Returns the next host id.
+     *
+     * @return the next host id
+     */
+    public HostId nextHostId() {
+        return HostId.hostId(MacAddress.valueOf(nextHostId), VlanId.NONE);
+    }
+
+    /**
+     * Returns the identifier of the device with the specified alias.
+     *
+     * @param name device name
+     * @return device identifier
+     */
+    public DeviceId deviceId(String name) {
+        return nameToId.get(name);
+    }
+
+    /**
+     * Creates simulated device.
+     *
+     * @param id        device identifier
+     * @param name      device name
+     * @param type      device type
+     * @param portCount number of device ports
+     */
+    public void createDevice(DeviceId id, String name, Device.Type type, int portCount) {
+        int chassisId = Integer.parseInt(id.uri().getSchemeSpecificPart());
+        createDevice(id, chassisId, type, portCount);
+        nameToId.put(name, id);
+    }
+
+    @Override
+    protected void createDevices() {
+    }
+
+    @Override
+    protected void createLinks() {
+    }
+
+    @Override
+    protected void createHosts() {
+    }
+}