From: http://www.cisco.com/en/US/docs/telepresence/infrastructure/articles/cisco_telepresence_packet_loss_poor_quality_audio_visual_one_direction_kb_82.shtml

• If you are seeing a lot of packet loss in one direction, this could be caused by a duplex mismatch somewhere in your network.
• If you are new to video conferencing over IP, you may have had a duplex mismatch in your network for some time: TCP traffic will be slowed down by it - and this may pass unnoticed - but UDP traffic will be lost.

From: http://msdn.microsoft.com/en-us/library/aa259670(v=sql.80).aspx

• In Control Panel, open Administrative Tools, and then open Performance.
• In the Windows Performance tool, expand Performance Logs and Alerts, right-click Counter Logs, and then click New Log Settings

From: http://social.technet.microsoft.com/Forums/en-US/winserverPN/thread/35f79821-7ab5-4335-89d5-cec58fa31d33/

If you want to monitor the amount of UDP packet loss you are experiencing I would use the performance logs and alerts utility.  The counter I
believe you would be interested in is under the UDP performance object, counter being "Datagrams Received Errors".  Also, you can query any
of these counters via WMI.