The TCP/IP Guide  9  TCP/IP Application Layer Protocols, Services and Applications (OSI Layers 5, 6 and 7)       9  TCP/IP Key Applications and Application Protocols            9  TCP/IP Administration and Troubleshooting Utilities and Protocols

TCP/IP Communication Verification Utility (ping/ping6) 1 2 3 4 TCP/IP Address Resolution Protocol Utility (arp)

The ping utility described in the preceding topic is extremely helpful for checking whether or not two devices are able to talk to each other. However, it provides very little information regarding what is going on between those two devices. In the event that ping shows either a total inability to communicate or intermittent connectivity with high loss of transmitted data, we need to know more about what is happening to IP datagrams as they are carried across the internetwork. This is especially important when the two devices are far from each other, especially if we are trying to reach a server on the public Internet.

I described in my overview of IP datagram delivery that when two devices are not on the same network, data sent between them must be delivered from one network to the next until it reaches its destination. This means that any time data is sent from device A on one network to device B on another, it follows a route, which may not be the same for each transmission.

When communication problems arise, it is very useful to be able to check the specific route taken by data between two devices. A special route tracing utility is provided for this function, called traceroute (abbreviated tracert in Windows systems, a legacy of the old eight-character limit for DOS program names). The IPv6 equivalent of this program is called traceroute6.

TCP/IP Communication Verification Utility (ping/ping6) 1 2 3 4 TCP/IP Address Resolution Protocol Utility (arp)