LFT (Layer Four Traceroute) is a sort of "traceroute" that often works much
faster than the commonly-used Van Jacobson method and goes through many
many configurations of packet-filter based firewalls.

More importantly, LFT implements numerous other features, including AS number
lookups through several reliable sources, loose source routing, netblock name
lookups, and more.

LFT also distinguishes between TCP-based protocols, which make its statistics
slightly more realistic, and gives a savvy user the ability to trace protocol
routes, not just layer-3 hops.