Sketched out packet service and related abstractions.
diff --git a/cli/src/main/java/org/onlab/onos/cli/net/TopologyCommand.java b/cli/src/main/java/org/onlab/onos/cli/net/TopologyCommand.java
index a390025..6c141ae 100644
--- a/cli/src/main/java/org/onlab/onos/cli/net/TopologyCommand.java
+++ b/cli/src/main/java/org/onlab/onos/cli/net/TopologyCommand.java
@@ -12,6 +12,7 @@
          description = "Lists summary of the current topology")
 public class TopologyCommand extends AbstractShellCommand {
 
+    // TODO: format the time-stamp
     private static final String FMT =
             "time=%s, devices=%d, links=%d, clusters=%d, paths=%d";