* Ping no more
“Ping,” a command that was designed – and used for many years – to confirm communication with and/or round-trip latency to an IP address or URL, has become much less useful. And this is really a shame, especially considering that the term has even made it into our everyday usage. Want to find out if somebody received a message or you need to remind them of something? Then we “ping” them.
The “ping problem” is that, like so many parts of IP (and TCP and UDP), ping was designed assuming that network users would play by the rules of common decency. The problem is that this assumption is no longer valid.
In fact, “ping” was one of the first commands to be exploited for denial-of-service attacks with the “ping of death” and variants thereof. Consequently, many hosts are now being protected by simply not responding to “pings.” This is effective, but it also renders ping useless as a diagnostic tool.
Tracert (Trace Route) is a similar but more powerful command. The Windows tracert command, which is most likely to be found as a “quick and dirty” diagnostic tool in the corporate environment, pings each router between the destination and the target, providing round-trip latency to each router. Thus, if poor performance were noted between two network endpoints, tracert would be able to help pinpoint the most likely bottleneck. (Our resident IP guru, Gary Kessler from Champlain College, points out that the Unix traceroute uses UDP datagrams and ICMP Time Exceeded and Port Unreachable messages. Although not ping-based, many sites also block these messages which effectively disables traceroute, as well.)
The impact of this loss was recently brought home to Steve when he was visiting his alma mater and talking with a student about perceived poor network performance. Being the geek that he is, Steve wanted to see this so, after observing the performance, he suggested doing a tracert to some common sites. Total failure.
Why? It turns out that not only were the endpoint routers not responding to the pings in the tracert; the pings were being filtered and not allowed off campus. This way, the college could responsibly ensure that ping-based denial-of-service attacks could not propagate from the campus network.
That’s the good news and the bad news. We’re safer from these attacks, but in the process, we’ve lost a rudimentary yet favorite first-line tool. We’d like to hear your opinions on this, so just ping us if you want to share an opinion.
