Layer Four Traceroute (LFT) is a fast, multi-protocol
traceroute
In computing, traceroute and tracert are computer network diagnostic commands for displaying possible routes (paths) and measuring transit delays of packets across an Internet Protocol (IP) network. The history of the route is recorded as th ...
engine, that also implements numerous other features including
AS number
As, AS, A. S., A/S or similar may refer to:
Art, entertainment, and media
* A. S. Byatt (born 1936), English critic, novelist, poet and short story writer
* "As" (song), by Stevie Wonder
* , a Spanish sports newspaper
* , an academic male voice ...
lookups through
regional Internet registries
A regional Internet registry (RIR) is an organization that manages the allocation and registration of Internet number resources within a region of the world. Internet number resources include IP addresses and autonomous system (AS) numbers.
T ...
and other reliable sources,
Loose Source Routing
There are a number of optional parameters that may be present in an Internet Protocol version 4 datagram. They typically configure a number of behaviors such as for the method to be used during source routing, some control and probing facilities an ...
,
firewall
Firewall may refer to:
* Firewall (computing), a technological barrier designed to prevent unauthorized or unwanted communications between computer networks or hosts
* Firewall (construction), a barrier inside a building, designed to limit the spre ...
and load balancer detection, etc. LFT is best known for its use by
network security
Network security consists of the policies, policies, processes and practices adopted to prevent, detect and monitor unauthorized access, Abuse, misuse, modification, or denial of a computer network and network-accessible resources. Network securi ...
practitioners to trace a route to a destination host through many configurations of packet-filters /
firewalls, and to detect network connectivity, performance or latency problems.
How it works
LFT sends various
TCP
TCP may refer to:
Science and technology
* Transformer coupled plasma
* Tool Center Point, see Robot end effector
Computing
* Transmission Control Protocol, a fundamental Internet standard
* Telephony control protocol, a Bluetooth communication s ...
SYN and FIN probes (differing from
Van Jacobson
Van Jacobson (born 1950) is an American computer scientist, renowned for his work on TCP/IP network performance and scaling. 's
UDP-based
method
Method ( grc, μέθοδος, methodos) literally means a pursuit of knowledge, investigation, mode of prosecuting such inquiry, or system. In recent centuries it more often means a prescribed process for completing a task. It may refer to:
*Scien ...
) or
UDP probes utilizing the
IP protocol
The Internet Protocol (IP) is the network layer communications protocol in the Internet protocol suite for relaying datagrams across network boundaries. Its routing function enables internetworking, and essentially establishes the Internet.
IP h ...
time to live
Time to live (TTL) or hop limit is a mechanism which limits the lifespan or lifetime of data in a computer or network. TTL may be implemented as a counter or timestamp attached to or embedded in the data. Once the prescribed event count or timesp ...
field and attempts to elicit an
ICMP TIME_EXCEEDED response from each
gateway along the path to some host. LFT also listens for various TCP, UDP, and ICMP messages along the way to assist network managers in ascertaining per-protocol
heuristic routing Heuristic routing is a system used to describe how deliveries are made when problems in a network topology arise. Heuristic is an adjective used in relation to methods of learning, discovery, or problem solving. Routing is the process of selecting p ...
information, and can optionally retrieve various information about the networks it traverses. The operation of layer four traceroute is described in detail in several prominent security books.
[The Tao of Network Security Monitoring (2004) Addison-Wesley ]
Origins
The
lft command first appeared in 1998 as
fft. Renamed as a result of confusion with
fast Fourier transform
A fast Fourier transform (FFT) is an algorithm that computes the discrete Fourier transform (DFT) of a sequence, or its inverse (IDFT). Fourier analysis converts a signal from its original domain (often time or space) to a representation in th ...
s, lft stands for ''layer four traceroute''. Results are often referred to as a ''layer four trace''.
See also
*
Prefix WhoIs
Sources
External links
Layer Four Traceroute Project
{{DEFAULTSORT:Layer Four Traceroute
Network analyzers