encapsulation constraint related to ONOS-3445

Change-Id: I5f7d912e34c343703108e0cb95c4ea94290663a8
diff --git a/core/api/src/main/java/org/onosproject/net/EncapsulationType.java b/core/api/src/main/java/org/onosproject/net/EncapsulationType.java
new file mode 100644
index 0000000..63ff46d
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/net/EncapsulationType.java
@@ -0,0 +1,30 @@
+/*
+ * 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.net;
+
+public enum EncapsulationType {
+    /**
+     * Indicates an MPLS encapsulation.
+     */
+    MPLS,
+    /**
+     * Indicates a VLAN encapsulation.
+     */
+    VLAN,
+};
+
+