Traceroute
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Winxp-tracert.png
traceroute is a TCP/IP utility which allows the user to determine the route packets take to reach a particular host. traceroute works by increasing the "time to live" value of each successive packet sent. The first packet has a time to live (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.
On modern Unix and Linux-based operating systems, the traceroute utility by default uses UDP datagrams with a destination port number starting at 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. There is also traceroute implementation using TCP packets, such as tcptraceroute (http://michael.toren.net/code/tcptraceroute/)
In Microsoft Windows, traceroute is named tracert. A new utility, pathping, was introduced with Windows NT, combining ping and traceroute functionality.
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Example
Estonia to the United States. 195.80.96.219 (kauge.aso.ee) to 130.94.122.199 (larousse.wikipedia.org).
1 kauge.aso.ee 2 et-gw.aso.ee 3 kjj-bb2-fe-0-1-4.ee.estpak.ee 4 noe-bb2-ge-0-0-0-1.ee.estpak.ee 5 s-b3-pos0-3.telia.net 6 s-bb1-pos1-2-0.telia.net 7 adm-bb1-pos1-1-0.telia.net 8 adm-b1-pos2-0.telia.net 9 p4-1-2-0.r00.amstnl02.nl.bb.verio.net 10 p4-0-3-0.r01.amstnl02.nl.bb.verio.net 11 p4-0-1-0.r80.nwrknj01.us.bb.verio.net 12 p4-0-3-0.r00.nwrknj01.us.bb.verio.net 13 p16-0-1-1.r20.mlpsca01.us.bb.verio.net 14 xe-1-2-0.r21.mlpsca01.us.bb.verio.net 15 xe-0-2-0.r21.snjsca04.us.bb.verio.net 16 p64-0-0-0.r21.lsanca01.us.bb.verio.net 17 p16-3-0-0.r01.sndgca01.us.bb.verio.net 18 ge-1-2.a03.sndgca01.us.da.verio.net 19 larousse.wikipedia.org
Origins
The traceroute man page states that the original traceroute program was written by Van Jacobson in 1987 from a suggestion by Steve Deering, with particularly cogent suggestions or fixes from C. Philip Wood, Tim Seaver and Ken Adelman.
Uses
Traceroute can also be used for network troubleshooting. It, by showing a list of the routers, allows the user to identify faulty routers or router loops that may create problems for data to be transfered.
External links
- RFC792 (http://www.ietf.org/rfc/rfc0792.txt), Internet Control Message Protocol (ICMP)
- traceroute.org (http://www.traceroute.org) - Monthly updated list of online traceroutes
- BGP4.net Traceroute Wiki (http://www.bgp4.net/tr)
- [1] (http://www.internetipaddress.com/traceroute.aspx) - Free Visual Traceroute
- This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL.