In wireless link, Packet loss may caused by the high channel bit error rate and nodes mobile, and multi-path routing and node switching will lead to reorder.

That is, a visitor will have a .visit_FOO() and .depart_FOO() method for each type of node, rather than switching on type within large .startElement() and endElement() methods.

At the switching node, the label or payload extraction can be realized simply through an optical bandpass or notch filter respectively.