diff --git a/src/main/java/net/onrc/onos/ofcontroller/networkgraph/NetworkGraph.java b/src/main/java/net/onrc/onos/ofcontroller/networkgraph/NetworkGraph.java
index eff5952..45e4188 100644
--- a/src/main/java/net/onrc/onos/ofcontroller/networkgraph/NetworkGraph.java
+++ b/src/main/java/net/onrc/onos/ofcontroller/networkgraph/NetworkGraph.java
@@ -8,18 +8,76 @@
  * The northbound interface to the topology network graph. This interface
  * is presented to the rest of ONOS. It is currently read-only, as we want
  * only the discovery modules to be allowed to modify the topology.
- *
  */
 public interface NetworkGraph {
-	public Switch getSwitch(Long dpid);
-	public Iterable<Switch> getSwitches();
+    /**
+     * Get the switch for a given switch DPID.
+     *
+     * @param dpid the switch dpid.
+     * @return the switch if found, otherwise, null.
+     */
+    public Switch getSwitch(Long dpid);
 
-	// TODO Not sure about the use-case of this method? Remove if not used at the end.
-	public Iterable<Link> getLinks();
-	// XXX next 2 method can be removed. getSwitch(dpid).getOutgoingLinks() is equivalent
-	public Iterable<Link> getOutgoingLinksFromSwitch(Long dpid); // Toshi: unnecessary
-	public Iterable<Link> getIncomingLinksFromSwitch(Long dpid); // Toshi: unnecessary
+    /**
+     * Get all switches in the network.
+     *
+     * @return all switches in the network.
+     */
+    public Iterable<Switch> getSwitches();
 
-	public Iterable<Device> getDeviceByIp(InetAddress ipAddress);
-	public Device getDeviceByMac(MACAddress address);
+    /**
+     * Get the port on a switch.
+     *
+     * @param dpid the switch DPID.
+     * @param number the switch port number.
+     * @return the switch port if found, otherwise, null.
+     */
+    public Port getPort(Long dpid, Long number);
+
+    /**
+     * Get all links in the network.
+     *
+     * TODO: Not clear if this method is needed. Remove if not used.
+     *
+     * @return all links in the network.
+     */
+    public Iterable<Link> getLinks();
+
+    /**
+     * Get all outgoing links for a switch.
+     *
+     * TODO: Not clear if this method is needed. Remove if not used.
+     * E.g, getSwitch(dpid).getOutgoingLinks() is equivalent.
+     *
+     * @param dpid the switch DPID.
+     * @return all outgoing links for a switch.
+     */
+    public Iterable<Link> getOutgoingLinksFromSwitch(Long dpid);
+
+    /**
+     * Get all incoming links for a switch.
+     *
+     * TODO: Not clear if this method is needed. Remove if not used.
+     * E.g, getSwitch(dpid).getIncomingLinks() is equivalent.
+     *
+     * @param dpid the switch DPID.
+     * @return all incoming links for a switch.
+     */
+    public Iterable<Link> getIncomingLinksFromSwitch(Long dpid);
+
+    /**
+     * Get the network devices for a given IP address.
+     *
+     * @param ipAddress the IP address to use.
+     * @return the network devices for the IP address.
+     */
+    public Iterable<Device> getDevicesByIp(InetAddress ipAddress);
+
+    /**
+     * Get the network device for a given MAC address.
+     *
+     * @param address the MAC address to use.
+     * @return the network device for the MAC address if found, otherwise null.
+     */
+    public Device getDeviceByMac(MACAddress address);
 }
diff --git a/src/main/java/net/onrc/onos/ofcontroller/networkgraph/NetworkGraphImpl.java b/src/main/java/net/onrc/onos/ofcontroller/networkgraph/NetworkGraphImpl.java
index 4425a7d..628ad7c 100644
--- a/src/main/java/net/onrc/onos/ofcontroller/networkgraph/NetworkGraphImpl.java
+++ b/src/main/java/net/onrc/onos/ofcontroller/networkgraph/NetworkGraphImpl.java
@@ -53,6 +53,15 @@
 	}
 
 	@Override
+	public Port getPort(Long dpid, Long number) {
+	    Switch sw = getSwitch(dpid);
+	    if (sw != null) {
+		return sw.getPort(number);
+	    }
+	    return null;
+	}
+
+	@Override
 	public Iterable<Link> getLinks() {
 		List<Link> linklist = new LinkedList<>();
 
@@ -103,7 +112,7 @@
 
 
 	@Override
-	public Iterable<Device> getDeviceByIp(InetAddress ipAddress) {
+	public Iterable<Device> getDevicesByIp(InetAddress ipAddress) {
 		Set<Device> devices = addr2Device.get(ipAddress);
 		if (devices == null) {
 			return Collections.emptySet();
diff --git a/src/main/java/net/onrc/onos/ofcontroller/networkgraph/TopologyManager.java b/src/main/java/net/onrc/onos/ofcontroller/networkgraph/TopologyManager.java
index 4d56fed..fc57b3b 100644
--- a/src/main/java/net/onrc/onos/ofcontroller/networkgraph/TopologyManager.java
+++ b/src/main/java/net/onrc/onos/ofcontroller/networkgraph/TopologyManager.java
@@ -413,7 +413,8 @@
 	}
 
 	private boolean prepareForRemovePortEvent(PortEvent portEvt) {
-		Port port = getPort(portEvt.getDpid(), portEvt.getNumber());
+		Port port = networkGraph.getPort(portEvt.getDpid(),
+						 portEvt.getNumber());
 		if ( port == null ) {
 		    log.debug("Port already removed? {}", portEvt);
 		    // let it pass
@@ -453,8 +454,10 @@
 
 	private boolean prepareForAddLinkEvent(LinkEvent linkEvt) {
 	    // Src/Dst Port must exist
-	    Port srcPort = getPort(linkEvt.getSrc().dpid, linkEvt.getSrc().number);
-	    Port dstPort = getPort(linkEvt.getDst().dpid, linkEvt.getDst().number);
+	    Port srcPort = networkGraph.getPort(linkEvt.getSrc().dpid,
+						linkEvt.getSrc().number);
+	    Port dstPort = networkGraph.getPort(linkEvt.getDst().dpid,
+						linkEvt.getDst().number);
 	    if ( srcPort == null || dstPort == null ) {
 	    log.warn("Dropping add link event because port doesn't exist: {}",
 	    		linkEvt);
@@ -483,8 +486,10 @@
 
 	private boolean prepareForRemoveLinkEvent(LinkEvent linkEvt) {
 	    // Src/Dst Port must exist
-	    Port srcPort = getPort(linkEvt.getSrc().dpid, linkEvt.getSrc().number);
-	    Port dstPort = getPort(linkEvt.getDst().dpid, linkEvt.getDst().number);
+	    Port srcPort = networkGraph.getPort(linkEvt.getSrc().dpid,
+						linkEvt.getSrc().number);
+	    Port dstPort = networkGraph.getPort(linkEvt.getDst().dpid,
+						linkEvt.getDst().number);
 	    if ( srcPort == null || dstPort == null ) {
 		log.warn("Dropping remove link event because port doesn't exist {}", linkEvt);
 		return false;
@@ -515,7 +520,7 @@
 	    ArrayList<PortEvent.SwitchPort> failedSwitchPort = new ArrayList<>();
 	    for ( PortEvent.SwitchPort swp : deviceEvt.getAttachmentPoints() ) {
 		// Attached Ports must exist
-		Port port = getPort(swp.dpid, swp.number);
+		Port port = networkGraph.getPort(swp.dpid, swp.number);
 		if ( port == null ) {
 		    preconditionBroken = true;
 		    failedSwitchPort.add(swp);
@@ -792,7 +797,8 @@
 		throw new IllegalArgumentException("Link cannot be null");
 	    }
 
-	    Port srcPort = getPort(linkEvt.getSrc().dpid, linkEvt.getSrc().number);
+	    Port srcPort = networkGraph.getPort(linkEvt.getSrc().dpid,
+						linkEvt.getSrc().number);
 	    if (srcPort == null) {
 		throw new BrokenInvariantException(
 			String.format(
@@ -800,7 +806,8 @@
 				linkEvt.getSrc() ));
 	    }
 
-	    Port dstPort = getPort(linkEvt.getDst().dpid, linkEvt.getDst().number);
+	    Port dstPort = networkGraph.getPort(linkEvt.getDst().dpid,
+						linkEvt.getDst().number);
 	    if (dstPort == null) {
 		throw new BrokenInvariantException(
 			String.format(
@@ -861,13 +868,15 @@
 		throw new IllegalArgumentException("Link cannot be null");
 	    }
 
-	    Port srcPort = getPort(linkEvt.getSrc().dpid, linkEvt.getSrc().number);
+	    Port srcPort = networkGraph.getPort(linkEvt.getSrc().dpid,
+						linkEvt.getSrc().number);
 	    if (srcPort == null) {
 		log.warn("Src Port for Link {} already removed, ignoring", linkEvt);
 		return;
 	    }
 
-	    Port dstPort = getPort(linkEvt.getDst().dpid, linkEvt.getDst().number);
+	    Port dstPort = networkGraph.getPort(linkEvt.getDst().dpid,
+						linkEvt.getDst().number);
 	    if (dstPort == null) {
 		log.warn("Dst Port for Link {} already removed, ignoring", linkEvt);
 		return;
@@ -908,7 +917,7 @@
 	    // for each attachment point
 	    for (SwitchPort swp : deviceEvt.getAttachmentPoints() ) {
 		// Attached Ports must exist
-		Port port = getPort(swp.dpid, swp.number);
+		Port port = networkGraph.getPort(swp.dpid, swp.number);
 		if ( port == null ) {
 		    log.warn("Port for the attachment point {} did not exist. skipping mutation", swp);
 		    continue;
@@ -941,7 +950,7 @@
 	    // for each attachment point
 	    for (SwitchPort swp : deviceEvt.getAttachmentPoints() ) {
 		// Attached Ports must exist
-		Port port = getPort(swp.dpid, swp.number);
+		Port port = networkGraph.getPort(swp.dpid, swp.number);
 		if ( port == null ) {
 		    log.warn("Port for the attachment point {} did not exist. skipping attachment point mutation", swp);
 		    continue;
@@ -1011,15 +1020,6 @@
 	    }
 	}
 
-	// we might want to include this in NetworkGraph interface
-	private Port getPort(Long dpid, Long number) {
-	    Switch sw = networkGraph.getSwitch(dpid);
-	    if (sw != null) {
-		return sw.getPort(number);
-	    }
-	    return null;
-	}
-
 	private SwitchImpl getSwitchImpl(Switch sw) {
 	    if (sw instanceof SwitchImpl) {
 		return (SwitchImpl) sw;
@@ -1077,8 +1077,10 @@
 
 	    for (RCLink l : RCLink.getAllLinks()) {
 		// check if src/dst switch/port exist before triggering event
-		Port srcPort = getPort(l.getSrc().dpid, l.getSrc().number);
-		Port dstPort = getPort(l.getDst().dpid, l.getDst().number);
+		Port srcPort = networkGraph.getPort(l.getSrc().dpid,
+						    l.getSrc().number);
+		Port dstPort = networkGraph.getPort(l.getDst().dpid,
+						    l.getDst().number);
 		if ( srcPort == null || dstPort == null ) {
 		    continue;
 		}