Port Mirroring is used on a network switches to send a copy of network packets seen on one or several switch ports to another switch port, usually connected to a network analyzer tool (appliance or software). Applications include Intrusion Detection System (IDS), debugging, statistics and performances... Such system is generally referred to as Switched Port Analyzer (SPAN) on Cisco Switches or as Roving Analysis Port (RAP) on 3Com switches.
VDE switch is a virtual ethernet switch used to link several virtual machines, on the same computer or across a set of physical computer over the Internet. VDE is part of virtualsquare project ( http://wiki.virtualsquare.org/ )