diff --git a/app/src/main/java/org/onosproject/segmentrouting/grouphandler/DefaultGroupHandler.java b/app/src/main/java/org/onosproject/segmentrouting/grouphandler/DefaultGroupHandler.java
index 3cf1331..1e0e6fd 100644
--- a/app/src/main/java/org/onosproject/segmentrouting/grouphandler/DefaultGroupHandler.java
+++ b/app/src/main/java/org/onosproject/segmentrouting/grouphandler/DefaultGroupHandler.java
@@ -188,7 +188,8 @@
     }
 
     /**
-     * Updates local stores for link-src device/port to neighbor (link-dst).
+     * Updates local stores for link-src-device/port to neighbor (link-dst) for
+     * link that has come up.
      *
      * @param link the infrastructure link
      */
@@ -207,11 +208,13 @@
     }
 
     /**
-     * Updates local stores for port that has gone down.
+     * Updates local stores for link-src-device/port to neighbor (link-dst) for
+     * link that has gone down.
      *
-     * @param port port number that has gone down
+     * @param link the infrastructure link
      */
-    public void portDown(PortNumber port) {
+    public void portDownForLink(Link link) {
+        PortNumber port = link.src().port();
         if (portDeviceMap.get(port) == null) {
             log.warn("portDown: unknown port");
             return;
@@ -224,6 +227,18 @@
     }
 
     /**
+     * Cleans up local stores for removed neighbor device.
+     *
+     * @param neighborId the device identifier for the neighbor device
+     */
+    public void cleanUpForNeighborDown(DeviceId neighborId) {
+        Set<PortNumber> ports = devicePortMap.remove(neighborId);
+        if (ports != null) {
+            ports.forEach(p -> portDeviceMap.remove(p));
+        }
+    }
+
+    /**
      * Checks all groups in the src-device of link for neighbor sets that include
      * the dst-device of link, and edits the hash groups according to link up
      * or down. Should only be called by the master instance of the src-switch
@@ -248,8 +263,11 @@
                 .stream()
                 .filter(entry -> entry.getKey().deviceId().equals(deviceId))
                 // Filter out PW transit groups or include them if MPLS ECMP is supported
-                .filter(entry -> !entry.getKey().destinationSet().mplsSet() ||
-                        (entry.getKey().destinationSet().mplsSet() && srManager.getMplsEcmp()))
+                .filter(entry -> !entry.getKey().destinationSet().notBos() ||
+                        (entry.getKey().destinationSet().notBos() && srManager.getMplsEcmp()))
+                // Filter out simple SWAP groups or include them if MPLS ECMP is supported
+                .filter(entry -> !entry.getKey().destinationSet().swap() ||
+                        (entry.getKey().destinationSet().swap() && srManager.getMplsEcmp()))
                 .filter(entry -> entry.getValue().containsNextHop(link.dst().deviceId()))
                 .map(entry -> entry.getKey())
                 .collect(Collectors.toSet());
@@ -452,6 +470,21 @@
             int edgeLabel = dskey.destinationSet().getEdgeLabel(destSw);
             Integer nextId = nhops.nextId();
 
+            // some store elements may not be hashed next-objectives - ignore them
+            if (isSimpleNextObjective(dskey)) {
+                log.debug("Ignoring {} of SIMPLE nextObj for targetSw:{}"
+                        + " -> dstSw:{} with current nextHops:{} to new"
+                        + " nextHops: {} in nextId:{}",
+                          (revoke) ? "removal" : "addition", targetSw, destSw,
+                          currNeighbors, nextHops, nextId);
+                if ((revoke && !nextHops.isEmpty())
+                        || (!revoke && !nextHops.equals(currNeighbors))) {
+                    log.warn("Simple next objective cannot be edited to "
+                            + "move from {} to {}", currNeighbors, nextHops);
+                }
+                continue;
+            }
+
             if (currNeighbors == null || nextHops == null) {
                 log.warn("fixing hash groups but found currNeighbors:{} or nextHops:{}"
                         + " in targetSw:{} for dstSw:{}", currNeighbors, nextHops,
@@ -514,6 +547,7 @@
                                new NextNeighbors(currentNextHops.dstNextHops(),
                                                  currentNextHops.nextId()));
         }
+
         // even if one fails and others succeed, return false so ECMPspg not updated
         return success;
     }
@@ -615,6 +649,18 @@
     }
 
     /**
+     * Returns true if the destination set is meant for swap or multi-labeled
+     * packet transport, and MPLS ECMP is not supported.
+     *
+     * @param dskey the key representing the destination set
+     * @return true if destination set is meant for simple next objectives
+     */
+    boolean isSimpleNextObjective(DestinationSetNextObjectiveStoreKey dskey) {
+        return (dskey.destinationSet().notBos() || dskey.destinationSet().swap())
+                && !srManager.getMplsEcmp();
+    }
+
+    /**
      * Adds or removes a port that has been configured with a vlan to a broadcast group
      * for bridging. Should only be called by the master instance for this device.
      *
@@ -678,23 +724,26 @@
     }
 
     /**
-     * Returns the next objective of type hashed associated with the destination set.
-     * In addition, updates the existing next-objective if new route-route paths found
-     * have resulted in the addition of new next-hops to a particular destination.
-     * If there is no existing next objective for this destination set, this method
-     * would create a next objective and return the nextId. Optionally metadata can be
-     * passed in for the creation of the next objective.
+     * Returns the next objective of type hashed (or simple) associated with the
+     * destination set. In addition, updates the existing next-objective if new
+     * route-paths found have resulted in the addition of new next-hops to a
+     * particular destination. If there is no existing next objective for this
+     * destination set, this method would create a next objective and return the
+     * nextId. Optionally metadata can be passed in for the creation of the next
+     * objective. If the parameter simple is true then a simple next objective
+     * is created instead of a hashed one.
      *
      * @param ds destination set
      * @param nextHops a map of per destination next hops
      * @param meta metadata passed into the creation of a Next Objective
-     * @param isBos if Bos is set
+     * @param simple if true, a simple next objective will be created instead of
+     *            a hashed next objective
      * @return int if found or -1 if there are errors in the creation of the
-     *          neighbor set.
+     *         neighbor set.
      */
     public int getNextObjectiveId(DestinationSet ds,
                                   Map<DeviceId, Set<DeviceId>> nextHops,
-                                  TrafficSelector meta, boolean isBos) {
+                                  TrafficSelector meta, boolean simple) {
         NextNeighbors next = dsNextObjStore.
                 get(new DestinationSetNextObjectiveStoreKey(deviceId, ds));
         if (next == null) {
@@ -708,7 +757,7 @@
                       (nsStoreEntry.getKey().deviceId().equals(deviceId)))
                       .collect(Collectors.toList()));
 
-            createGroupFromDestinationSet(ds, nextHops, meta, isBos);
+            createGroupFromDestinationSet(ds, nextHops, meta, simple);
             next = dsNextObjStore.
                     get(new DestinationSetNextObjectiveStoreKey(deviceId, ds));
             if (next == null) {
@@ -833,39 +882,38 @@
         }
 
         // Update portToDevice database
-        DeviceId prev = portDeviceMap.putIfAbsent(portToNeighbor, neighborId);
+        // should always update as neighbor could have changed on this port
+        DeviceId prev = portDeviceMap.put(portToNeighbor, neighborId);
         if (prev != null) {
-            log.debug("Device: {} port: {} already has neighbor: {} ",
+            log.debug("Device/port: {}/{} previous neighbor: {}, current neighbor: {} ",
                       deviceId, portToNeighbor, prev, neighborId);
         }
     }
 
     /**
      * Creates a NextObjective for a hash group in this device from a given
-     * DestinationSet.
+     * DestinationSet. If the parameter simple is true, a simple next objective
+     * is created instead.
      *
      * @param ds the DestinationSet
      * @param neighbors a map for each destination and its next-hops
      * @param meta metadata passed into the creation of a Next Objective
-     * @param isBos if BoS is set
+     * @param simple if true, a simple next objective will be created instead of
+     *            a hashed next objective
      */
     public void createGroupFromDestinationSet(DestinationSet ds,
                                               Map<DeviceId, Set<DeviceId>> neighbors,
                                               TrafficSelector meta,
-                                              boolean isBos) {
+                                              boolean simple) {
         int nextId = flowObjectiveService.allocateNextId();
-        NextObjective.Type type = NextObjective.Type.HASHED;
+        NextObjective.Type type = (simple) ? NextObjective.Type.SIMPLE
+                                           : NextObjective.Type.HASHED;
         if (neighbors == null || neighbors.isEmpty()) {
             log.warn("createGroupsFromDestinationSet: needs at least one neighbor"
                     + "to create group in dev:{} for ds: {} with next-hops {}",
                     deviceId, ds, neighbors);
             return;
         }
-        // If Bos == False and MPLS-ECMP == false, we have
-        // to use simple group and we will pick a single neighbor for a single dest.
-        if (!isBos && !srManager.getMplsEcmp()) {
-            type = NextObjective.Type.SIMPLE;
-        }
 
         NextObjective.Builder nextObjBuilder = DefaultNextObjective
                 .builder()
@@ -878,7 +926,7 @@
 
         // create treatment buckets for each neighbor for each dst Device
         // except in the special case where we only want to pick a single
-        // neighbor for a simple group
+        // neighbor/port for a simple nextObj
         boolean foundSingleNeighbor = false;
         boolean treatmentAdded = false;
         Map<DeviceId, Set<DeviceId>> dstNextHops = new ConcurrentHashMap<>();
@@ -912,8 +960,8 @@
                 }
                 // For each port to the neighbor, we create a new treatment
                 Set<PortNumber> neighborPorts = devicePortMap.get(neighborId);
-                // In this case we are using a SIMPLE group. We randomly pick a port
-                if (!isBos && !srManager.getMplsEcmp()) {
+                // In this case we need a SIMPLE nextObj. We randomly pick a port
+                if (simple) {
                     int size = devicePortMap.get(neighborId).size();
                     int index = RandomUtils.nextInt(0, size);
                     neighborPorts = Collections.singleton(
@@ -928,9 +976,14 @@
                     tBuilder.setEthDst(neighborMac).setEthSrc(nodeMacAddr);
                     int edgeLabel = ds.getEdgeLabel(dst);
                     if (edgeLabel != DestinationSet.NO_EDGE_LABEL) {
-                        tBuilder.pushMpls()
-                        .copyTtlOut()
-                        .setMpls(MplsLabel.mplsLabel(edgeLabel));
+                        if (simple) {
+                            // swap label case
+                            tBuilder.setMpls(MplsLabel.mplsLabel(edgeLabel));
+                        } else {
+                            // ecmp with label push case
+                            tBuilder.pushMpls().copyTtlOut()
+                                    .setMpls(MplsLabel.mplsLabel(edgeLabel));
+                        }
                     }
                     tBuilder.setOutput(sp);
                     nextObjBuilder.addTreatment(tBuilder.build());
@@ -1395,8 +1448,11 @@
                         .stream()
                         .filter(entry -> entry.getKey().deviceId().equals(deviceId))
                         // Filter out PW transit groups or include them if MPLS ECMP is supported
-                        .filter(entry -> !entry.getKey().destinationSet().mplsSet() ||
-                                (entry.getKey().destinationSet().mplsSet() && srManager.getMplsEcmp()))
+                        .filter(entry -> !entry.getKey().destinationSet().notBos() ||
+                                (entry.getKey().destinationSet().notBos() && srManager.getMplsEcmp()))
+                        // Filter out simple SWAP groups or include them if MPLS ECMP is supported
+                        .filter(entry -> !entry.getKey().destinationSet().swap() ||
+                                (entry.getKey().destinationSet().swap() && srManager.getMplsEcmp()))
                         .map(entry -> entry.getKey())
                         .collect(Collectors.toSet());
                 for (DestinationSetNextObjectiveStoreKey dsKey : dsKeySet) {
@@ -1434,8 +1490,11 @@
                                         + " port/label {}/{} to dst {} via {}",
                                         deviceId, nid, port, edgeLabel,
                                         dstDev, neighbor);
-                                nextObjBuilder.addTreatment(treatmentBuilder(port,
-                                                                neighborMac, edgeLabel));
+                                nextObjBuilder
+                                    .addTreatment(treatmentBuilder(port,
+                                                                   neighborMac,
+                                                                   dsKey.destinationSet().swap(),
+                                                                   edgeLabel));
                             });
                         });
                     });
@@ -1450,16 +1509,22 @@
         }
 
         TrafficTreatment treatmentBuilder(PortNumber outport, MacAddress dstMac,
-                                          int edgeLabel) {
+                                          boolean swap, int edgeLabel) {
             TrafficTreatment.Builder tBuilder =
                     DefaultTrafficTreatment.builder();
             tBuilder.setOutput(outport)
                 .setEthDst(dstMac)
                 .setEthSrc(nodeMacAddr);
             if (edgeLabel != DestinationSet.NO_EDGE_LABEL) {
-                tBuilder.pushMpls()
-                    .copyTtlOut()
-                    .setMpls(MplsLabel.mplsLabel(edgeLabel));
+                if (swap) {
+                    // swap label case
+                    tBuilder.setMpls(MplsLabel.mplsLabel(edgeLabel));
+                } else {
+                    // ecmp with label push case
+                    tBuilder.pushMpls()
+                        .copyTtlOut()
+                        .setMpls(MplsLabel.mplsLabel(edgeLabel));
+                }
             }
             return tBuilder.build();
         }
diff --git a/app/src/main/java/org/onosproject/segmentrouting/grouphandler/DestinationSet.java b/app/src/main/java/org/onosproject/segmentrouting/grouphandler/DestinationSet.java
index 7f839cf..0626bc8 100644
--- a/app/src/main/java/org/onosproject/segmentrouting/grouphandler/DestinationSet.java
+++ b/app/src/main/java/org/onosproject/segmentrouting/grouphandler/DestinationSet.java
@@ -28,15 +28,17 @@
 import static org.slf4j.LoggerFactory.getLogger;
 
 /**
- * Representation of a set of destination switch dpids along with their edge-node
- * labels. Meant to be used as a lookup-key in a hash-map to retrieve an ECMP-group
- * that hashes packets towards a specific destination switch,
- * or paired-destination switches.
+ * Representation of a set of destination switch dpids along with their
+ * edge-node labels. Meant to be used as a lookup-key in a hash-map to retrieve
+ * an ECMP-group that hashes packets towards a specific destination switch, or
+ * paired-destination switches. May also be used to represent cases where the
+ * forwarding does not use ECMP groups (ie SIMPLE next objectives)
  */
 public class DestinationSet {
     public static final int NO_EDGE_LABEL = -1;
     private static final int NOT_ASSIGNED = 0;
-    private boolean mplsSet;
+    private boolean notBos; // XXX replace with enum
+    private boolean swap; // XXX replace with enum
     private final DeviceId dstSw1;
     private final int edgeLabel1;
     private final DeviceId dstSw2;
@@ -48,12 +50,14 @@
     /**
      * Constructor for a single destination with no Edge label.
      *
-     * @param isMplsSet indicates if it is a mpls destination set
+     * @param isNotBos indicates if it is meant for a non bottom-of-stack label
+     * @param isSwap indicates if it is meant for a swap action
      * @param dstSw the destination switch
      */
-    public DestinationSet(boolean isMplsSet, DeviceId dstSw) {
+    public DestinationSet(boolean isNotBos, boolean isSwap, DeviceId dstSw) {
         this.edgeLabel1 = NO_EDGE_LABEL;
-        this.mplsSet = isMplsSet;
+        this.notBos = isNotBos;
+        this.swap = isSwap;
         this.dstSw1 = dstSw;
         this.edgeLabel2 = NOT_ASSIGNED;
         this.dstSw2 = null;
@@ -62,13 +66,15 @@
     /**
      * Constructor for a single destination with Edge label.
      *
-     * @param isMplsSet indicates if it is a mpls destination set
+     * @param isNotBos indicates if it is meant for a non bottom-of-stack label
+     * @param isSwap indicates if it is meant for a swap action
      * @param edgeLabel label to be pushed as part of group operation
      * @param dstSw the destination switch
      */
-    public DestinationSet(boolean isMplsSet,
+    public DestinationSet(boolean isNotBos, boolean isSwap,
                        int edgeLabel, DeviceId dstSw) {
-        this.mplsSet = isMplsSet;
+        this.notBos = isNotBos;
+        this.swap = isSwap;
         this.edgeLabel1 = edgeLabel;
         this.dstSw1 = dstSw;
         this.edgeLabel2 = NOT_ASSIGNED;
@@ -76,19 +82,23 @@
     }
 
     /**
-     * Constructor for paired destination switches and their associated
-     * edge labels.
+     * Constructor for paired destination switches and their associated edge
+     * labels.
      *
-     * @param isMplsSet indicates if it is a mpls destination set
-     * @param edgeLabel1 label to be pushed as part of group operation for dstSw1
+     * @param isNotBos indicates if it is meant for a non bottom-of-stack label
+     * @param isSwap indicates if it is meant for a swap action
+     * @param edgeLabel1 label to be pushed as part of group operation for
+     *            dstSw1
      * @param dstSw1 one of the paired destination switches
-     * @param edgeLabel2 label to be pushed as part of group operation for dstSw2
+     * @param edgeLabel2 label to be pushed as part of group operation for
+     *            dstSw2
      * @param dstSw2 the other paired destination switch
      */
-    public DestinationSet(boolean isMplsSet,
+    public DestinationSet(boolean isNotBos, boolean isSwap,
                           int edgeLabel1, DeviceId dstSw1,
                           int edgeLabel2, DeviceId dstSw2) {
-        this.mplsSet = isMplsSet;
+        this.notBos = isNotBos;
+        this.swap = isSwap;
         if (dstSw1.toString().compareTo(dstSw2.toString()) <= 0) {
             this.edgeLabel1 = edgeLabel1;
             this.dstSw1 = dstSw1;
@@ -108,52 +118,13 @@
     public DestinationSet() {
         this.edgeLabel1 = NOT_ASSIGNED;
         this.edgeLabel2 = NOT_ASSIGNED;
-        this.mplsSet = true;
+        this.notBos = true;
+        this.swap = true;
         this.dstSw1 = DeviceId.NONE;
         this.dstSw2 = DeviceId.NONE;
     }
 
     /**
-     * Factory method for DestinationSet hierarchy.
-     *
-     * @param random the expected behavior.
-     * @param isMplsSet indicates if it is a mpls destination set
-     * @param dstSw the destination switch
-     * @return the destination set object.
-     */
-    public static DestinationSet destinationSet(boolean random,
-                                          boolean isMplsSet, DeviceId dstSw) {
-        return random ? new RandomDestinationSet(dstSw)
-                      : new DestinationSet(isMplsSet, dstSw);
-    }
-
-    /**
-     * Factory method for DestinationSet hierarchy.
-     *
-     * @param random the expected behavior.
-     * @param isMplsSet indicates if it is a mpls destination set
-     * @param edgeLabel label to be pushed as part of group operation
-     * @param dstSw the destination switch
-     * @return the destination set object
-     */
-    public static DestinationSet destinationSet(boolean random,
-                                          boolean isMplsSet, int edgeLabel,
-                                          DeviceId dstSw) {
-        return random ? new RandomDestinationSet(edgeLabel, dstSw)
-                      : new DestinationSet(isMplsSet, edgeLabel, dstSw);
-    }
-
-    /**
-     * Factory method for DestinationSet hierarchy.
-     *
-     * @param random the expected behavior.
-     * @return the destination set object
-     */
-    public static DestinationSet destinationSet(boolean random) {
-        return random ? new RandomDestinationSet() : new DestinationSet();
-    }
-
-    /**
      * Gets the label associated with given destination switch.
      *
      * @param dstSw the destination switch
@@ -183,12 +154,21 @@
     }
 
     /**
-     * Gets the value of mplsSet.
+     * Gets the value of notBos.
      *
-     * @return the value of mplsSet
+     * @return the value of notBos
      */
-    public boolean mplsSet() {
-        return mplsSet;
+    public boolean notBos() {
+        return notBos;
+    }
+
+    /**
+     * Gets the value of swap.
+     *
+     * @return the value of swap
+     */
+    public boolean swap() {
+        return swap;
     }
 
     // The list of destination ids and label are used for comparison.
@@ -202,7 +182,8 @@
         }
         DestinationSet that = (DestinationSet) o;
         boolean equal = (this.edgeLabel1 == that.edgeLabel1 &&
-                            this.mplsSet == that.mplsSet &&
+                            this.notBos == that.notBos &&
+                            this.swap == that.swap &&
                             this.dstSw1.equals(that.dstSw1));
         if (this.dstSw2 != null && that.dstSw2 == null ||
                 this.dstSw2 == null && that.dstSw2 != null) {
@@ -219,15 +200,26 @@
     @Override
     public int hashCode() {
         if (dstSw2 == null) {
-            return Objects.hash(mplsSet, edgeLabel1, dstSw1);
+            return Objects.hash(notBos, swap, edgeLabel1, dstSw1);
         }
-        return Objects.hash(mplsSet, edgeLabel1, dstSw1, edgeLabel2, dstSw2);
+        return Objects.hash(notBos, swap, edgeLabel1, dstSw1, edgeLabel2,
+                            dstSw2);
     }
 
     @Override
     public String toString() {
+        String type;
+        if (!notBos && !swap) {
+            type = "default";
+        } else if (!notBos && swap) {
+            type = "swapbos";
+        } else if (notBos && !swap) {
+            type = "not-bos";
+        } else {
+            type = "swap-nb";
+        }
         ToStringHelper h = toStringHelper(this)
-                                .add("MplsSet", mplsSet)
+                                .add("Type", type)
                                 .add("DstSw1", dstSw1)
                                 .add("Label1", edgeLabel1);
         if (dstSw2 != null) {
diff --git a/app/src/main/java/org/onosproject/segmentrouting/grouphandler/RandomDestinationSet.java b/app/src/main/java/org/onosproject/segmentrouting/grouphandler/RandomDestinationSet.java
deleted file mode 100644
index 3671b03..0000000
--- a/app/src/main/java/org/onosproject/segmentrouting/grouphandler/RandomDestinationSet.java
+++ /dev/null
@@ -1,60 +0,0 @@
-/*
- * Copyright 2016-present Open Networking Foundation
- *
- * 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.segmentrouting.grouphandler;
-
-import org.onosproject.net.DeviceId;
-
-/**
- * Extends its super class modifying its internal behavior.
- * Pick a neighbor will pick a random neighbor.
- */
-public class RandomDestinationSet extends DestinationSet {
-
-    public RandomDestinationSet(DeviceId dstSw) {
-        super(true, dstSw);
-    }
-
-    public RandomDestinationSet(int edgeLabel,
-                             DeviceId dstSw) {
-        super(true, edgeLabel, dstSw);
-    }
-
-    public RandomDestinationSet() {
-        super();
-    }
-
-    // XXX revisit the need for this class since neighbors no longer stored here
-    // will be handled when we fix pseudowires for dual-Tor scenarios
-
-
-    /*@Override
-    public DeviceId getFirstNeighbor() {
-        if (getDeviceIds().isEmpty()) {
-            return DeviceId.NONE;
-        }
-        int size = getDeviceIds().size();
-        int index = RandomUtils.nextInt(0, size);
-        return Iterables.get(getDeviceIds(), index);
-    }*/
-
-    @Override
-    public String toString() {
-        return " RandomNeighborset Sw: " //+ getDeviceIds()
-                + " and Label: " //+ getEdgeLabel()
-                + " for destination: "; // + getDestinationSw();
-    }
-}