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 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.