diff --git a/app/src/main/java/org/onosproject/t3/api/FlowNib.java b/app/src/main/java/org/onosproject/t3/api/FlowNib.java
index b9f2226..1b70551 100644
--- a/app/src/main/java/org/onosproject/t3/api/FlowNib.java
+++ b/app/src/main/java/org/onosproject/t3/api/FlowNib.java
@@ -67,7 +67,7 @@
                 .filter(flow -> flow.state() == flowState
                         && flow.deviceId().equals(deviceId))
                 .collect(Collectors.toSet());
-        return flowsFiltered != null ? ImmutableSet.copyOf(flowsFiltered) : ImmutableSet.of();
+        return ImmutableSet.copyOf(flowsFiltered);
     }
 
     /**
diff --git a/app/src/main/java/org/onosproject/t3/api/GroupNib.java b/app/src/main/java/org/onosproject/t3/api/GroupNib.java
index b1fb563..14f55a7 100644
--- a/app/src/main/java/org/onosproject/t3/api/GroupNib.java
+++ b/app/src/main/java/org/onosproject/t3/api/GroupNib.java
@@ -56,6 +56,21 @@
     }
 
     /**
+     * Returns all groups associated with the given device and filtered by the group state.
+     *
+     * @param deviceId device ID to get groups for
+     * @param groupState the group state
+     * @return iterable of device's groups
+     */
+    public Iterable<Group> getGroupsByState(DeviceId deviceId, Group.GroupState groupState) {
+        Set<Group> groupsFiltered = groups.stream()
+                .filter(group -> group.state() == groupState
+                        && group.deviceId().equals(deviceId))
+                .collect(Collectors.toSet());
+        return ImmutableSet.copyOf(groupsFiltered);
+    }
+
+    /**
      * Returns all groups associated with the given device.
      *
      * @param deviceId device ID to get groups for
@@ -63,9 +78,9 @@
      */
     public Iterable<Group> getGroups(DeviceId deviceId) {
         Set<Group> groupsFiltered = groups.stream()
-                .filter(g -> g.deviceId().equals(deviceId))
+                .filter(group -> group.deviceId().equals(deviceId))
                 .collect(Collectors.toSet());
-        return groupsFiltered != null ? ImmutableSet.copyOf(groupsFiltered) : ImmutableSet.of();
+        return ImmutableSet.copyOf(groupsFiltered);
     }
 
     /**
diff --git a/app/src/main/java/org/onosproject/t3/api/GroupsInDevice.java b/app/src/main/java/org/onosproject/t3/api/GroupsInDevice.java
index 74203af..b17cfbb 100644
--- a/app/src/main/java/org/onosproject/t3/api/GroupsInDevice.java
+++ b/app/src/main/java/org/onosproject/t3/api/GroupsInDevice.java
@@ -25,8 +25,9 @@
 
 /**
  * Class to represent the groups in a device for a given output and packet.
+ * @deprecated in t3-4.0
  */
-//FIXME consider name change.
+@Deprecated
 public class GroupsInDevice {
 
     private ConnectPoint output;
diff --git a/app/src/main/java/org/onosproject/t3/api/StaticPacketTrace.java b/app/src/main/java/org/onosproject/t3/api/StaticPacketTrace.java
index 22db007..57e1dce 100644
--- a/app/src/main/java/org/onosproject/t3/api/StaticPacketTrace.java
+++ b/app/src/main/java/org/onosproject/t3/api/StaticPacketTrace.java
@@ -21,6 +21,7 @@
 import org.onosproject.net.ConnectPoint;
 import org.onosproject.net.DeviceId;
 import org.onosproject.net.Host;
+import org.onosproject.net.PipelineTraceableHitChain;
 import org.onosproject.net.flow.FlowEntry;
 import org.onosproject.net.flow.TrafficSelector;
 
@@ -36,10 +37,11 @@
  */
 public class StaticPacketTrace {
 
-    private final TrafficSelector inPacket;
-    private final ConnectPoint in;
+    private final TrafficSelector ingressPacket;
+    private final ConnectPoint ingressPoint;
     List<List<ConnectPoint>> completePaths;
     private Map<DeviceId, List<GroupsInDevice>> outputsForDevice;
+    private Map<DeviceId, List<PipelineTraceableHitChain>> hitChainsForDevice;
     private Map<DeviceId, List<FlowEntry>> flowsForDevice;
     private StringBuilder resultMessage;
     private Pair<Host, Host> hosts;
@@ -48,15 +50,16 @@
     /**
      * Builds the trace with a given packet and a connect point.
      *
-     * @param packet the packet to trace
-     * @param in     the initial connect point
+     * @param inPacket the packet to trace
+     * @param inPoint  the initial connect point
      */
-    public StaticPacketTrace(TrafficSelector packet, ConnectPoint in) {
-        this.inPacket = packet;
-        this.in = in;
+    public StaticPacketTrace(TrafficSelector inPacket, ConnectPoint inPoint) {
+        this.ingressPacket = inPacket;
+        this.ingressPoint = inPoint;
         completePaths = new ArrayList<>();
         outputsForDevice = new HashMap<>();
         flowsForDevice = new HashMap<>();
+        hitChainsForDevice = new HashMap<>();
         resultMessage = new StringBuilder();
         hosts = null;
     }
@@ -64,16 +67,17 @@
     /**
      * Builds the trace with a given packet and a connect point.
      *
-     * @param packet the packet to trace
-     * @param in     the initial connect point
-     * @param hosts  pair of source and destination hosts
+     * @param inPacket the packet to trace
+     * @param inPoint  the initial connect point
+     * @param hosts    pair of source and destination hosts
      */
-    public StaticPacketTrace(TrafficSelector packet, ConnectPoint in, Pair<Host, Host> hosts) {
-        this.inPacket = packet;
-        this.in = in;
+    public StaticPacketTrace(TrafficSelector inPacket, ConnectPoint inPoint, Pair<Host, Host> hosts) {
+        this.ingressPacket = inPacket;
+        this.ingressPoint = inPoint;
         completePaths = new ArrayList<>();
         outputsForDevice = new HashMap<>();
         flowsForDevice = new HashMap<>();
+        hitChainsForDevice = new HashMap<>();
         resultMessage = new StringBuilder();
         this.hosts = hosts;
     }
@@ -84,7 +88,7 @@
      * @return the initial packet in the form of a selector.
      */
     public TrafficSelector getInitialPacket() {
-        return inPacket;
+        return ingressPacket;
     }
 
     /**
@@ -93,7 +97,7 @@
      * @return the connect point
      */
     public ConnectPoint getInitialConnectPoint() {
-        return in;
+        return ingressPoint;
     }
 
     /**
@@ -122,7 +126,9 @@
      *
      * @param deviceId   the device
      * @param outputPath the groups in device objects
+     * @deprecated in t3-4.0
      */
+    @Deprecated
     public void addGroupOutputPath(DeviceId deviceId, GroupsInDevice outputPath) {
         if (!outputsForDevice.containsKey(deviceId)) {
             outputsForDevice.put(deviceId, new ArrayList<>());
@@ -131,16 +137,48 @@
     }
 
     /**
+     * Adds the pipeline hit chain for a given device.
+     *
+     * @param deviceId the device
+     * @param hitChain the hit chain
+     */
+    public void addHitChain(DeviceId deviceId, PipelineTraceableHitChain hitChain) {
+        hitChainsForDevice.compute(deviceId, (k, v) -> {
+            if (v == null) {
+                v = new ArrayList<>();
+            }
+            if (!v.contains(hitChain)) {
+                v.add(hitChain);
+            }
+            return v;
+        });
+    }
+
+    /**
      * Returns all the possible group-based outputs for a given device.
      *
      * @param deviceId the device
      * @return the list of Groups for this device.
+     * @deprecated in t3-4.0
      */
+    @Deprecated
     public List<GroupsInDevice> getGroupOuputs(DeviceId deviceId) {
         return outputsForDevice.get(deviceId) == null ? null : ImmutableList.copyOf(outputsForDevice.get(deviceId));
     }
 
     /**
+     * Returns all the possible pipeline hit chains for a given device.
+     *
+     * @param deviceId the device
+     * @return the list of hit chains
+     */
+    public List<PipelineTraceableHitChain> getHitChains(DeviceId deviceId) {
+        List<PipelineTraceableHitChain> hitChains = hitChainsForDevice.get(deviceId);
+        return hitChains == null ? null : ImmutableList.copyOf(hitChains);
+
+    }
+
+    /**
      * Adds a complete possible path.
      *
      * @param completePath the path
@@ -163,7 +201,9 @@
      *
      * @param deviceId the device considered
      * @param flows    the flows
+     * @deprecated in t3-4.0
      */
+    @Deprecated
     public void addFlowsForDevice(DeviceId deviceId, List<FlowEntry> flows) {
         flowsForDevice.put(deviceId, flows);
     }
@@ -173,7 +213,9 @@
      *
      * @param deviceId the device
      * @return the flows matched
+     * @deprecated in t3-4.0
      */
+    @Deprecated
     public List<FlowEntry> getFlowsForDevice(DeviceId deviceId) {
         return flowsForDevice.getOrDefault(deviceId, ImmutableList.of());
     }
@@ -214,15 +256,15 @@
         this.success.add(success);
     }
 
-
     @Override
     public String toString() {
         return "StaticPacketTrace{" +
-                "inPacket=" + inPacket +
-                ", in=" + in +
+                "ingressPacket=" + ingressPacket +
+                ", ingressPoint=" + ingressPoint +
                 ", completePaths=" + completePaths +
                 ", outputsForDevice=" + outputsForDevice +
                 ", flowsForDevice=" + flowsForDevice +
+                ", hitChains=" + hitChainsForDevice +
                 ", resultMessage=" + resultMessage +
                 '}';
     }
diff --git a/app/src/main/java/org/onosproject/t3/api/TroubleshootService.java b/app/src/main/java/org/onosproject/t3/api/TroubleshootService.java
index 3ab6052..d9c2f59 100644
--- a/app/src/main/java/org/onosproject/t3/api/TroubleshootService.java
+++ b/app/src/main/java/org/onosproject/t3/api/TroubleshootService.java
@@ -18,10 +18,10 @@
 
 import org.onlab.packet.EthType;
 import org.onlab.packet.VlanId;
+import org.onlab.util.Generator;
 import org.onosproject.net.ConnectPoint;
 import org.onosproject.net.HostId;
 import org.onosproject.net.flow.TrafficSelector;
-import org.onosproject.t3.impl.Generator;
 
 import java.util.List;
 import java.util.Set;
@@ -37,7 +37,9 @@
      *
      * @param type the etherType of the traffic we want to trace.
      * @return trace result
+     * @deprecated in t3-4.0
      */
+    @Deprecated
     List<StaticPacketTrace> pingAll(EthType.EtherType type);
 
     /**
@@ -81,7 +83,9 @@
      *
      * @param vlanId the vlan id configured for multicast
      * @return list of trace result
+     * @deprecated in t3-4.0
      */
+    @Deprecated
     List<Set<StaticPacketTrace>> getMulitcastTrace(VlanId vlanId);
 
     /**