diff --git a/src/main/java/net/onrc/onos/core/topology/HostEvent.java b/src/main/java/net/onrc/onos/core/topology/HostEvent.java
new file mode 100644
index 0000000..8747079
--- /dev/null
+++ b/src/main/java/net/onrc/onos/core/topology/HostEvent.java
@@ -0,0 +1,159 @@
+package net.onrc.onos.core.topology;
+
+import java.nio.ByteBuffer;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Objects;
+
+import net.floodlightcontroller.util.MACAddress;
+import net.onrc.onos.core.topology.web.serializers.HostEventSerializer;
+import net.onrc.onos.core.util.SwitchPort;
+
+import org.codehaus.jackson.map.annotate.JsonSerialize;
+
+/**
+ * Self-contained Host event(s) Object
+ * <p/>
+ * Host event differ from other events.
+ * Host Event represent add/remove of attachmentPoint.
+ * Not add/remove of the DeviceObject itself.
+ * <p/>
+ * Multiple attachmentPoints can be specified to batch events into 1 object.
+ * Each should be treated as independent events.
+ * <p/>
+ * TODO: Rename to match what it is. (Switch/Port/Link/Host)Snapshot?
+ * FIXME: Current implementation directly use this object as
+ *        Replication message, but should be sending update operation info.
+ */
+@JsonSerialize(using = HostEventSerializer.class)
+public class HostEvent extends TopologyElement<HostEvent> {
+
+    private final MACAddress mac;
+    private List<SwitchPort> attachmentPoints;
+    private long lastSeenTime;
+
+    /**
+     * Default constructor for Serializer to use.
+     */
+    @Deprecated
+    protected HostEvent() {
+        mac = null;
+    }
+
+    public HostEvent(MACAddress mac) {
+        if (mac == null) {
+            throw new IllegalArgumentException("Host mac cannot be null");
+        }
+        this.mac = mac;
+        this.attachmentPoints = new LinkedList<>();
+    }
+
+    /**
+     * Creates an unfrozen copy of given Object.
+     *
+     * @param original to make copy of.
+     */
+    public HostEvent(HostEvent original) {
+        super(original);
+        this.mac = original.mac;
+        this.attachmentPoints = new ArrayList<>(original.attachmentPoints);
+    }
+
+
+    public MACAddress getMac() {
+        return mac;
+    }
+
+    public List<SwitchPort> getAttachmentPoints() {
+        return Collections.unmodifiableList(attachmentPoints);
+    }
+
+    public void setAttachmentPoints(List<SwitchPort> attachmentPoints) {
+        if (isFrozen()) {
+            throw new IllegalStateException("Tried to modify frozen instance: " + this);
+        }
+        this.attachmentPoints = attachmentPoints;
+    }
+
+    public void addAttachmentPoint(SwitchPort attachmentPoint) {
+        if (isFrozen()) {
+            throw new IllegalStateException("Tried to modify frozen instance: " + this);
+        }
+        // may need to maintain uniqueness
+        this.attachmentPoints.add(0, attachmentPoint);
+    }
+
+    public boolean removeAttachmentPoint(SwitchPort attachmentPoint) {
+        if (isFrozen()) {
+            throw new IllegalStateException("Tried to modify frozen instance: " + this);
+        }
+        return this.attachmentPoints.remove(attachmentPoint);
+    }
+
+
+    public long getLastSeenTime() {
+        return lastSeenTime;
+    }
+
+    public void setLastSeenTime(long lastSeenTime) {
+        if (isFrozen()) {
+            throw new IllegalStateException("Tried to modify frozen instance: " + this);
+        }
+        this.lastSeenTime = lastSeenTime;
+    }
+
+    @Override
+    public String toString() {
+        return "[HostEvent " + mac + " attachmentPoints:" + attachmentPoints + "]";
+    }
+
+    @Override
+    public int hashCode() {
+        final int prime = 31;
+        int result = super.hashCode();
+        result = prime * result
+                + ((attachmentPoints == null) ? 0 : attachmentPoints.hashCode());
+        result = prime * result + ((mac == null) ? 0 : mac.hashCode());
+        return result;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+
+        if (obj == null) {
+            return false;
+        }
+
+        if (getClass() != obj.getClass()) {
+            return false;
+        }
+        HostEvent other = (HostEvent) obj;
+
+        if (!super.equals(obj)) {
+            return false;
+        }
+
+        // XXX lastSeenTime excluded from Equality condition, is it OK?
+        return Objects.equals(mac, other.mac) &&
+                Objects.equals(this.attachmentPoints, other.attachmentPoints);
+    }
+
+    // Assuming mac is unique cluster-wide
+    public static ByteBuffer getDeviceID(final byte[] mac) {
+        return (ByteBuffer) ByteBuffer.allocate(2 + mac.length)
+                .putChar('D').put(mac).flip();
+    }
+
+    public byte[] getID() {
+        return getDeviceID(mac.toBytes()).array();
+    }
+
+    public ByteBuffer getIDasByteBuffer() {
+        return getDeviceID(mac.toBytes());
+    }
+}