This is the blog of Ronald Bartels that wanders on and off the subject of problem management (that is how it started), but it is best described by Ray who says this is Daddy's thoughts! Like the best music is from the Eighties and a wee dram helps in solving most inconveniences.
LFT, short for 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-filters
(firewalls). More importantly, LFT implements numerous other features
including AS number lookups through several reliable sources, loose
source routing, netblock name lookups, et al.
What makes LFT unique? LFT is the all-in-one traceroute tool
because it can launch a variety of different probes using ICMP, UDP, and
TCP protocols, or the RFC1393 trace method. For example, rather than
only launching UDP probes in an attempt to elicit ICMP "TTL exceeded"
from hosts in the path, LFT can send TCP SYN or FIN probes to target
arbitrary services. Then, LFT listens for "TTL exceeded" messages, TCP
RST (reset), and various other interesting heuristics from firewalls or
other gateways in the path. LFT also distinguishes between TCP-based
protocols (source and destination), which make its statistics slightly
more realistic, and gives a savvy user the ability to trace protocol
routes, not just layer-3 (IP) hops. With LFT's verbose output, much can
be discovered about a target network.