Initial import of CFM and SOAM api

Change-Id: Icf5cc2d5fb34b75460e80e8cced0d70265bcd33b
diff --git a/incubator/api/src/main/java/org/onosproject/incubator/net/l2monitoring/soam/StopTime.java b/incubator/api/src/main/java/org/onosproject/incubator/net/l2monitoring/soam/StopTime.java
new file mode 100644
index 0000000..b581036
--- /dev/null
+++ b/incubator/api/src/main/java/org/onosproject/incubator/net/l2monitoring/soam/StopTime.java
@@ -0,0 +1,64 @@
+/*
+ * 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.incubator.net.l2monitoring.soam;
+
+import java.time.Duration;
+import java.time.Instant;
+
+import com.google.common.base.MoreObjects;
+
+/**
+ * A utility class for specifying a Stop Time for Delay and Loss Measurements.
+ */
+public final class StopTime extends SoamTime {
+
+    private StopTime(TimeOption option, Duration relativeStart, Instant absoluteStart) {
+        super(option, relativeStart, absoluteStart);
+    }
+
+    public static final StopTime none() {
+        return new StopTime(StopTimeOption.NONE, null, null);
+    }
+
+    public static final StopTime relative(Duration relativeStop) {
+        return new StopTime(StopTimeOption.RELATIVE, relativeStop, null);
+    }
+
+    public static final StopTime absolute(Instant absoluteStop) {
+        return new StopTime(StopTimeOption.ABSOLUTE, null, absoluteStop);
+    }
+
+    @Override
+    public String toString() {
+        if (option == StopTimeOption.NONE) {
+            return "none";
+        } else if (option == StopTimeOption.ABSOLUTE) {
+            return MoreObjects.toStringHelper(getClass()).add("absolute", absoluteTime).toString();
+        } else if (option == StopTimeOption.RELATIVE) {
+            return MoreObjects.toStringHelper(getClass()).add("relative", relativeTime).toString();
+        }
+        return "unknown";
+    }
+
+    /**
+     * Options for Stop Time.
+     */
+    public enum StopTimeOption implements TimeOption {
+        NONE,
+        RELATIVE,
+        ABSOLUTE;
+    }
+}
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