Sketched out packet service and related abstractions.
diff --git a/cli/src/main/java/org/onlab/onos/cli/net/ClusterLinksCommand.java b/cli/src/main/java/org/onlab/onos/cli/net/ClusterLinksCommand.java
index 5285418..246c39e 100644
--- a/cli/src/main/java/org/onlab/onos/cli/net/ClusterLinksCommand.java
+++ b/cli/src/main/java/org/onlab/onos/cli/net/ClusterLinksCommand.java
@@ -16,7 +16,7 @@
 public class ClusterLinksCommand extends ClustersListCommand {
 
     @Argument(index = 0, name = "id", description = "Cluster ID",
-              required = false, multiValued = false)
+              required = true, multiValued = false)
     String id = null;
 
     @Override
@@ -30,5 +30,4 @@
         return null;
     }
 
-
 }