Web design tools - other hand, if you can ping another machine
other hand, if you can ping another machine in your house or office but youcan t ping a machine elsewhere on the Internet, then something may bewrong with your connection to your ISP. Latency,or the amount of time it takes for a signal to travel on the Internet, has little to do with physical distance. Rather, factors such as network traffic, bandwidth, and network hardware all contribute to a slow latency. These fac- tors determine whether a pingto your neighbor s computer takes longerthan pinging a host at the South Pole. For example, try pinging Yahoo! by opening a command prompt (see Chapter 14) and typing the following command: ping www.yahoo.comPress Ctrl+C to stop the ping; otherwise, your computer continues to pingthe target. The output, as shown in Figure 8-6, provides information about what pingisdoing. If the ping can t reach the host, you receive a message that the host isunreachable. If the ping can reach the host, you receive feedback that provideshow long it takes in milliseconds (ms) for the signal from your computerto get to the destination computer and back again the lower the numbers, the better. For computers connected through Ethernet, a pingtime of 1 ms to 3ms is an acceptable response time. For dial-up connections, expect somewherearound 150 ms. When you start seeing pingtimes climbing to 900 ms or higher, the network is likely under heavy use (or you have something wrong with yourcables). Following in your traffic s footsteps with tracerouteAnother fun command is traceroute, which allows you to see all the com- puters your data goes through on its way to a destination. Simply type thecommand traceroute hostname, such as traceroute bob.example.comortraceroute 192.168.1.5. After a few moments, you receive a list of allcomputers between you and the designated hostname and how long it tookfor the data to travel to each one of them in turn, as shown in Figure 8-7. Try Yahoo.com! again as an example. Open a command prompt (see Chapter14), type tracerouteyahoo.com, and press Enter. It can take a moment forthe data to start filling in, but when it does, each line of your tracerouteresults represents a hop.Each hop represents a physical machine your datamust travel through in order to get where it s going. You can identify heavynetwork congestion and other problems by making note of the larger num- bers in the list. 162Part II:Internet Now!