+ /**
+ * The Fleet instruction encoding mechanism assumes that each
+ * source->dest path can be turned into a bitstring, and that the
+ * bitstring gives sufficient information to route the packet.
+ * Therefore, the interpreter assigns a "serial number" to every
+ * InterpreterDestination in a fleet and uses the serial number
+ * of the destination as the path.
+ */
+ private int serialNumber;
+ int getSerialNumber() { return serialNumber; }