Traceroute, originally written by Van Jacobson in 1988, is a TCP/IP utility which allows the user to determine the route packets take to reach a particular host. The term traceroute now refers both to a utility and the output of the utility. Traceroute shows you the address and how long it takes to get to each hop in the path. It can be very useful for locating and detecting network congestion, failures, and other various other troubleshooting issues.
Traceroute works by increasing the "time to live" value of each successive packet sent. The first packet has a TTL value of one, the second two, and so on. When a packet passes through a host, the host decrements the TTL value by one and forwards the packet to the next host. When a packet with a TTL of one reaches a host, the host discards the packet and sends an ICMP time exceeded (type 11) packet to the sender. The traceroute utility uses these returning packets to produce a list of hosts that the packets have traversed en route to the destination.
You can run your own traceroute software with a PPP or net connection. In Microsoft Windows, traceroute is named tracert. A similar tool, pathping, was introduced with Windows NT, combining ping and traceroute functionality. To run the traceroute tool in Windows environment, first type command to call a DOS window. Then type the command tracert delphiforums.com (or any other address). traceroute utility, which will trace only from Delphi back to your provider.--> NetLab is an excellent freeware program for Windows that includes traceroute and other utilities. NetLab is a freeware program for Windows that includes traceroute and other utilities. WS-FTP Pro, a popular shareware FTP program, also provides traceroute and other utilities in its package.
On Unix and Linux-based operating systems, the traceroute utility by default uses UDP datagrams with a port number of 33434. The traceroute utility usually has an option to specify use of ICMP echo request (type 8) instead. The Windows utility uses ICMP echo request, better known as ping packets. Some firewalls on the path being investigated may block UDP probes but allow the ICMP echo request traffic to pass through.
Traceroute does not provide any information regarding the physical location of each node along the route, which makes it difficult to effectively identify geographically circuitous unicast routing. Indeed, there are examples of paths between hosts just a few miles apart that cross the entire United States and back, phenomena not immediately evident from the textual output of traceroute. While such path information may not be of much interest to many end users, it can provide valuable insight to system administrators, network engineers, operators and analysts.
Related Terms: Ping, Pathping
Reference Links：http://www.tcpdump.org: The official site of tcpdump