DNS Name Resolution Process
(Page 3 of 3)
Changes to Resolution to Handle Special Cases
This example is highly simplified, and also only shows one possible way that servers might be set up. For one thing, it is possible that even though compsci.googleplex.edu is in a separate zone from googleplex.edu, they might use the same server. In that case, one iteration in the process would be skipped. The example also above doesn't show what happens if an error occurs in the process.
If the domain name entered was an alias, indicated by a CNAME record, this would change the processing as well. CNAME records are used to allow a constant name for a device to be presented to the outside world while allowing the actual device that corresponds to the name to vary inside the organization. When a CNAME is used, it changes the name resolution process by adding an extra step: first we resolve the alias to the canonical name and then resolve the canonical name.
For example, Web servers are almost always named starting with www., so at XYZ Industries we want people to be able to find our Web site at www.xyzindustries.com. However, the Web server may in fact be shared with other services on bigserver.xyzindustries.com. We can set up a CNAME record to point www.xyzindustries.com to bigserver.xyzindustries.com. Resolution of www will result in a CNAME pointing to bigserver, which is then itself resolved. If in the future our business grows and we decide to upgrade our Web service to run on biggerserver.xyzindustries.com, we just change the CNAME record and users are unaffected.
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Version 3.0 - Version Date: September 20, 2005
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