It’s a fact of life on a network that things go wrong. Hardware fails, software has bugs, and people occasionally make mistakes. Sometimes this results in minor inconveniences, like having a few users lose connections. Sometimes the results are catastrophic and involve the loss of important data and valuable jobs.
Because the Domain Name System relies so heavily on the network, it is vulnerable to network outages. Thankfully, the design of DNS takes into account the imperfection of networks: it allows for multiple, redundant name servers, retransmission of queries, retrying zone transfers, and so on.
DNS doesn’t protect itself from every conceivable calamity, though. There are types of network failures—some of them quite common—that DNS doesn’t or can’t protect against. But with a small investment of time and money, you can minimize the threat of these problems.
Power outages, for example, are relatively common in many parts of the world. In some parts of the U.S., thunderstorms or tornadoes may cause a site to lose power, or to have only intermittent power, for an extended period. Elsewhere, typhoons, volcanoes, or construction work may interrupt your electrical service. And at the time of this writing, those of you in California might lose power in a rolling blackout from lack of electrical capacity.
If all your hosts are down, of course, you don’t need name service. Quite often, however, sites have problems when power is restored. Following ...