Microsoft Network Monitor
From Federal Burro of Information
Useful filters
Property.TCPRetransmit==1
Source or desitnation
IPv4.Address == 192.168.0.1
see also:
http://www.ietf.org/rfc/rfc879.txt
Adjusting IP MTU, TCP MSS, and PMTUD on Windows and Sun Systems
http://www.cisco.com/en/US/tech/tk870/tk877/tk880/technologies_tech_note09186a008011a218.shtml