diff --git a/core/api/src/main/java/org/onlab/onos/net/flow/DefaultTrafficTreatment.java b/core/api/src/main/java/org/onlab/onos/net/flow/DefaultTrafficTreatment.java
index d206c97..6eaa2c3 100644
--- a/core/api/src/main/java/org/onlab/onos/net/flow/DefaultTrafficTreatment.java
+++ b/core/api/src/main/java/org/onlab/onos/net/flow/DefaultTrafficTreatment.java
@@ -6,7 +6,6 @@
 import java.util.LinkedList;
 import java.util.List;
 
-import org.onlab.onos.net.PortNumber;
 import org.slf4j.Logger;
 
 @SuppressWarnings("rawtypes")
@@ -33,29 +32,33 @@
 
         private final Logger log = getLogger(getClass());
 
-        List<Instruction<PortNumber>> outputs = new LinkedList<>();
+        boolean drop = false;
+
+        List<Instruction> outputs = new LinkedList<>();
 
         // TODO: should be a list of instructions based on group objects
-        List<Instruction<Object>> groups = new LinkedList<>();
+        List<Instruction> groups = new LinkedList<>();
 
         // TODO: should be a list of instructions based on modification objects
-        List<Instruction<Object>> modifications = new LinkedList<>();
+        List<Instruction> modifications = new LinkedList<>();
 
 
-        @SuppressWarnings("unchecked")
         @Override
         public Builder add(Instruction instruction) {
             switch (instruction.type()) {
-            case OUTPUT:
             case DROP:
-                // TODO: should check that there is only one drop instruction.
+                drop = true;
+                break;
+            case OUTPUT:
                 outputs.add(instruction);
                 break;
             case MODIFICATION:
                 // TODO: enforce modification order if any
                 modifications.add(instruction);
+                break;
             case GROUP:
                 groups.add(instruction);
+                break;
             default:
                 log.warn("Unknown instruction type {}", instruction.type());
             }
@@ -64,10 +67,14 @@
 
         @Override
         public TrafficTreatment build() {
+
+            //If we are dropping should we just return an emptry list?
             List<Instruction> instructions = new LinkedList<Instruction>();
             instructions.addAll(modifications);
             instructions.addAll(groups);
-            instructions.addAll(outputs);
+            if (!drop) {
+                instructions.addAll(outputs);
+            }
 
             return new DefaultTrafficTreatment(instructions);
         }
diff --git a/core/api/src/main/java/org/onlab/onos/net/flow/Instruction.java b/core/api/src/main/java/org/onlab/onos/net/flow/Instruction.java
index e9ea35b..0888d9b 100644
--- a/core/api/src/main/java/org/onlab/onos/net/flow/Instruction.java
+++ b/core/api/src/main/java/org/onlab/onos/net/flow/Instruction.java
@@ -4,7 +4,7 @@
  * Abstraction of a single traffic treatment step.
  * @param <T> the type parameter for the instruction
  */
-public interface Instruction<T> {
+public interface Instruction {
 
     /**
      * Represents the type of traffic treatment.
@@ -41,10 +41,4 @@
      */
     public Type type();
 
-    /**
-     * Returns the actual value of the instruction.
-     * @return the value for this instruction
-     */
-    public T instruction();
-
 }
diff --git a/core/api/src/main/java/org/onlab/onos/net/flow/Instructions.java b/core/api/src/main/java/org/onlab/onos/net/flow/Instructions.java
index f72b07e..9681076 100644
--- a/core/api/src/main/java/org/onlab/onos/net/flow/Instructions.java
+++ b/core/api/src/main/java/org/onlab/onos/net/flow/Instructions.java
@@ -1,7 +1,8 @@
 package org.onlab.onos.net.flow;
 
-import org.onlab.onos.net.PortNumber;
+import static com.google.common.base.Preconditions.checkNotNull;
 
+import org.onlab.onos.net.PortNumber;
 /**
  * Factory class for creating various traffic treatment instructions.
  */
@@ -17,22 +18,44 @@
      * @param number port number
      * @return output instruction
      */
-    public static Instruction<PortNumber> createOutput(final PortNumber number) {
-        return new Instruction<PortNumber>() {
+    public static OutputInstruction createOutput(final PortNumber number) {
+        checkNotNull(number, "PortNumber cannot be null");
+        return new OutputInstruction(number);
+    }
 
-            @Override
-            public Instruction.Type type() {
-                return Type.OUTPUT;
-            }
-
-            @Override
-            public PortNumber instruction() {
-                return number;
-            }
-
-        };
+    public static DropInstruction createDrop() {
+        return new DropInstruction();
     }
 
     // TODO: add create methods
 
+    public static final class DropInstruction implements Instruction {
+
+        @Override
+        public Type type() {
+            return Type.DROP;
+        }
+    }
+
+
+    public static final class OutputInstruction implements Instruction {
+
+        private final PortNumber port;
+
+        private OutputInstruction(PortNumber port) {
+            this.port = port;
+        }
+
+        public PortNumber port() {
+            return port;
+        }
+
+        @Override
+        public Type type() {
+            return Type.OUTPUT;
+        }
+
+
+    }
+
 }
diff --git a/core/api/src/main/java/org/onlab/onos/net/packet/DefaultPacketContext.java b/core/api/src/main/java/org/onlab/onos/net/packet/DefaultPacketContext.java
index 3c2b0ea..6f1b708 100644
--- a/core/api/src/main/java/org/onlab/onos/net/packet/DefaultPacketContext.java
+++ b/core/api/src/main/java/org/onlab/onos/net/packet/DefaultPacketContext.java
@@ -51,7 +51,7 @@
     public abstract void send();
 
     @Override
-    public boolean blocked() {
+    public boolean block() {
         return this.block.getAndSet(true);
     }
 
diff --git a/core/api/src/main/java/org/onlab/onos/net/packet/PacketContext.java b/core/api/src/main/java/org/onlab/onos/net/packet/PacketContext.java
index ce08fde..48cb084 100644
--- a/core/api/src/main/java/org/onlab/onos/net/packet/PacketContext.java
+++ b/core/api/src/main/java/org/onlab/onos/net/packet/PacketContext.java
@@ -45,7 +45,7 @@
      * Blocks the outbound packet from being sent from this point onward.
      * @return whether the outbound packet is blocked.
      */
-    boolean blocked();
+    boolean block();
 
     /**
      * Check whether the outbound packet is blocked.
diff --git a/core/api/src/test/java/org/onlab/onos/event/AbstractEventAccumulatorTest.java b/core/api/src/test/java/org/onlab/onos/event/AbstractEventAccumulatorTest.java
index c0cce92..9e561bf 100644
--- a/core/api/src/test/java/org/onlab/onos/event/AbstractEventAccumulatorTest.java
+++ b/core/api/src/test/java/org/onlab/onos/event/AbstractEventAccumulatorTest.java
@@ -1,13 +1,15 @@
 package org.onlab.onos.event;
 
-import org.junit.Test;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+import static org.onlab.junit.TestTools.delay;
+import static org.onlab.onos.event.TestEvent.Type.FOO;
 
 import java.util.List;
 import java.util.Timer;
 
-import static org.junit.Assert.*;
-import static org.onlab.junit.TestTools.delay;
-import static org.onlab.onos.event.TestEvent.Type.FOO;
+import org.junit.Test;
 
 /**
  * Tests the operation of the accumulator.