topology:  caida's skitter

track/depict topology cross-sections 
17 monitors (inc. some root name servers)
forward IP path and round-trip delay 
multiple dst lists (22k servers, 36k dns)
remove targets that complain

architecture
continuous, parallel ICMP probes
depending on dst list size, O(1) probes/hr/dst
52-byte packets
kernel time stamping
ssh / Kerberos

correlate path perf. w events, e.g. BGP
identify critical pieces of infrastructure
case studies of relevant cross-sections