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15.8 DNS Versus X.500

X.500 is an ISO (International Standards Organization) standard distributed directory system that's sometimes seen as a "competitor" to DNS. X.500 does, indeed, include some of the same functionality DNS does. For example, you can use X.500 to retrieve address information for a particular host. And in some ways, the two are similar: X.500 directories store data in hierarchical name spaces, and use recursion and iteration (well, ISO calls them "chaining" and "referral"). While we can hardly claim to be experts on X.500, we can make some general comparisons between DNS and X.500:

Anyway, you get the idea. X.500 is rich in capabilities and will be extremely useful when it is completely defined, implemented, and optimized. DNS provides a few, critical functions. It is, for the most part, fully implemented, and it will continue to evolve and improve.

Don't let this turn you off to DNS, though. The Domain Name System really is admirably good at its job, and it does it much faster than X.500 does. True, X.500 offers richer functionality, but it may never usurp DNS's position as the Internet's directory system of choice.

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