diff --git a/core/api/src/main/java/org/onosproject/store/service/MultiValuedTimestamp.java b/core/api/src/main/java/org/onosproject/store/service/MultiValuedTimestamp.java
new file mode 100644
index 0000000..e068b8e
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/store/service/MultiValuedTimestamp.java
@@ -0,0 +1,111 @@
+/*
+ * Copyright 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.store.service;
+
+import com.google.common.base.MoreObjects;
+import com.google.common.collect.ComparisonChain;
+import org.onosproject.store.Timestamp;
+
+import java.util.Objects;
+
+import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.base.Preconditions.checkNotNull;
+
+/**
+ * A logical timestamp that derives its value from two input values. The first
+ * value always takes precedence over the second value when comparing timestamps.
+ */
+public class MultiValuedTimestamp<T extends Comparable<T>, U extends Comparable<U>>
+        implements Timestamp {
+
+    private final T value1;
+    private final U value2;
+
+    /**
+     * Creates a new timestamp based on two values. The first value has higher
+     * precedence than the second when comparing timestamps.
+     *
+     * @param value1 first value
+     * @param value2 second value
+     */
+    public MultiValuedTimestamp(T value1, U value2) {
+        this.value1 = checkNotNull(value1);
+        this.value2 = checkNotNull(value2);
+    }
+
+    @Override
+    public int compareTo(Timestamp o) {
+        checkArgument(o instanceof MultiValuedTimestamp,
+                      "Must be MultiValuedTimestamp", o);
+        MultiValuedTimestamp that = (MultiValuedTimestamp) o;
+
+        return ComparisonChain.start()
+                .compare(this.value1, that.value1)
+                .compare(this.value2, that.value2)
+                .result();
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(value1, value2);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+        if (!(obj instanceof MultiValuedTimestamp)) {
+            return false;
+        }
+        MultiValuedTimestamp that = (MultiValuedTimestamp) obj;
+        return Objects.equals(this.value1, that.value1) &&
+                Objects.equals(this.value2, that.value2);
+    }
+
+    @Override
+    public String toString() {
+        return MoreObjects.toStringHelper(getClass())
+                .add("value1", value1)
+                .add("value2", value2)
+                .toString();
+    }
+
+    /**
+     * Returns the first value.
+     *
+     * @return first value
+     */
+    public T value1() {
+        return value1;
+    }
+
+    /**
+     * Returns the second value.
+     *
+     * @return second value
+     */
+    public U value2() {
+        return value2;
+    }
+
+    // Default constructor for serialization
+    @SuppressWarnings("unused")
+    private MultiValuedTimestamp() {
+        this.value1 = null;
+        this.value2 = null;
+    }
+}
diff --git a/core/api/src/main/java/org/onosproject/store/service/WallClockTimestamp.java b/core/api/src/main/java/org/onosproject/store/service/WallClockTimestamp.java
new file mode 100644
index 0000000..0cc7b45
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/store/service/WallClockTimestamp.java
@@ -0,0 +1,85 @@
+/*
+ * Copyright 2014 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.store.service;
+
+import static com.google.common.base.Preconditions.checkArgument;
+
+import java.util.Objects;
+
+import org.onosproject.store.Timestamp;
+
+import com.google.common.base.MoreObjects;
+import com.google.common.collect.ComparisonChain;
+
+/**
+ * A Timestamp that derives its value from the prevailing
+ * wallclock time on the controller where it is generated.
+ */
+public class WallClockTimestamp implements Timestamp {
+
+    private final long unixTimestamp;
+
+    public WallClockTimestamp() {
+        unixTimestamp = System.currentTimeMillis();
+    }
+
+    public WallClockTimestamp(long timestamp) {
+        unixTimestamp = timestamp;
+    }
+
+    @Override
+    public int compareTo(Timestamp o) {
+        checkArgument(o instanceof WallClockTimestamp,
+                "Must be WallClockTimestamp", o);
+        WallClockTimestamp that = (WallClockTimestamp) o;
+
+        return ComparisonChain.start()
+                .compare(this.unixTimestamp, that.unixTimestamp)
+                .result();
+    }
+    @Override
+    public int hashCode() {
+        return Objects.hash(unixTimestamp);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+        if (!(obj instanceof WallClockTimestamp)) {
+            return false;
+        }
+        WallClockTimestamp that = (WallClockTimestamp) obj;
+        return Objects.equals(this.unixTimestamp, that.unixTimestamp);
+    }
+
+    @Override
+    public String toString() {
+        return MoreObjects.toStringHelper(getClass())
+                    .add("unixTimestamp", unixTimestamp)
+                    .toString();
+    }
+
+    /**
+     * Returns the unixTimestamp.
+     *
+     * @return unix timestamp
+     */
+    public long unixTimestamp() {
+        return unixTimestamp;
+    }
+}
diff --git a/core/api/src/main/java/org/onosproject/store/service/WallclockClockManager.java b/core/api/src/main/java/org/onosproject/store/service/WallclockClockManager.java
new file mode 100644
index 0000000..c2b5ffb
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/store/service/WallclockClockManager.java
@@ -0,0 +1,28 @@
+/*
+ * Copyright 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.store.service;
+
+import org.onosproject.store.Timestamp;
+
+/**
+ * A clock service which hands out wallclock-based timestamps.
+ */
+public class WallclockClockManager<T, U> implements ClockService<T, U> {
+    @Override
+    public Timestamp getTimestamp(T object1, U object2) {
+        return new WallClockTimestamp();
+    }
+}