Began implementation of the a host monitor
diff --git a/core/api/src/main/java/org/onlab/onos/net/host/HostService.java b/core/api/src/main/java/org/onlab/onos/net/host/HostService.java
index 39f63c0..3717bea 100644
--- a/core/api/src/main/java/org/onlab/onos/net/host/HostService.java
+++ b/core/api/src/main/java/org/onlab/onos/net/host/HostService.java
@@ -1,5 +1,7 @@
 package org.onlab.onos.net.host;
 
+import java.util.Set;
+
 import org.onlab.onos.net.ConnectPoint;
 import org.onlab.onos.net.DeviceId;
 import org.onlab.onos.net.Host;
@@ -8,8 +10,6 @@
 import org.onlab.packet.MacAddress;
 import org.onlab.packet.VlanId;
 
-import java.util.Set;
-
 /**
  * Service for interacting with the inventory of end-station hosts.
  */
@@ -82,6 +82,22 @@
     Set<Host> getConnectedHosts(DeviceId deviceId);
 
     /**
+     * Requests the host service to monitor hosts with the given IP address and
+     * notify listeners of changes.
+     *
+     * @param ip IP address of the host to monitor
+     */
+    void monitorIp(IpPrefix ip);
+
+    /**
+     * Stops the host service from monitoring an IP address.
+     *
+     * @param ip IP address to stop monitoring
+     */
+    // TODO clients can cancel other client's requests
+    void stopMonitoringIp(IpPrefix ip);
+
+    /**
      * Adds the specified host listener.
      *
      * @param listener host listener