[ONOS-6551] Tunnel implementation for L3VPN service.

Change-Id: I3171a83305cb7391d80fda94ddf567629a10675e
diff --git a/apps/l3vpn/src/main/java/org/onosproject/l3vpn/netl3vpn/ModelIdLevel.java b/apps/l3vpn/src/main/java/org/onosproject/l3vpn/netl3vpn/ModelIdLevel.java
new file mode 100644
index 0000000..91bf248
--- /dev/null
+++ b/apps/l3vpn/src/main/java/org/onosproject/l3vpn/netl3vpn/ModelIdLevel.java
@@ -0,0 +1,59 @@
+/*
+ * Copyright 2017-present Open Networking Foundation
+ *
+ * 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.l3vpn.netl3vpn;
+
+/**
+ * Represents the model id level to add it in the store.
+ * //TODO: Further levels has to be added.
+ */
+public enum ModelIdLevel {
+
+    /**
+     * Requested model id level is not present, representing top node.
+     */
+    ROOT,
+
+    /**
+     * Requested model id level is devices container.
+     */
+    DEVICES,
+
+    /**
+     * Requested model id level is device list.
+     */
+    DEVICE,
+
+    /**
+     * Requested model id level is VPN list.
+     */
+    VPN,
+
+    /**
+     * Requested model id level is tunnel manager.
+     */
+    TNL_M,
+
+    /**
+     * Requested model id level is tunnel policy.
+     */
+    TNL_POL,
+
+    /**
+     * Requested model id level is tunnel hop.
+     */
+    TP_HOP
+}