A traceroute, in the simplest terms, is a way to see how information travels from one computer to another. Usually, information sent from one computer does not reach the destination computer in one single jump. In fact, it usually requires several computers to transmit the information. A traceroute identifies each computer on that list, and the amount of time it takes to get from one computer to another. If there is an interruption in the transfer of data, the traceroute will show where in the chain the problem occurred.
Each computer on the traceroute is identified by its IP address, which is a 9 digit number separated by periods. The journey from one computer to another is known as a 'hop.' The amount of time it takes to make a hop is measured in milliseconds. The information that travels along the traceroute is known as 'packets.' Generally, a traceroute will display three separate columns for the hop time, as each traceroute sends out three separate packets of information to each computer. At the very top of the list, the traceroute will give the limit of how many lines of hops it will display; 30 hops is a typical maximum number.
Aside from being an entertaining exercise, requesting a traceroute also has more practical uses. If you are having difficulty accessing a particular website or computer, for example, performing a traceroute allows you to quickly see where the problem is occurring. When a traceroute has difficulty accessing a computer, it will display the message "Request timed out." Each of the hop columns will display an asterisk instead of a millisecond count.
On occasion, a traceroute will show one hop time, with the next two columns displaying asterisks. This usually indicates that although one packet was accepted by the computer, the other two packets were discarded. This is not unusual; due to security concerns, many computers routinely reject multiple packages, or forward them to different sources.
In the past, hackers would routinely use traceroutes to map how information moved within a given company, and then hone their attacks. Now, certain networks will not allow you to perform a traceroute to eliminate this security threat. As long as you are not attempting to tap into heavily secured networks, you can perform a traceroute using the traceroute utility on the Windows operating system. To do this, you must know the domain name, IP address, or name of the computer itself that you are trying to reach. Using the utility, you would type 'tracert x' where x stands for either the IP address, the domain name, or the computer name. Also, if you are using the Macintosh OS X or any subsequent versions, you may use either the Terminal program, or the network utility to generate a traceroute. The utility will then display the traceroute on your screen.