UNIX System Administration Handbook - Evi Nemeth [240]
DNS domains should (must, in fact; see RFC1219) be served by at least two servers. One common arrangement is for a site to operate its own master server and to let the ISP’s servers act as a backup. Once the system has been configured, the ISP’s servers automatically download their configuration information from your master server. Changes made to the DNS configuration are reflected on the backup servers without any explicit work on the part of either site’s administrator.
Selecting a domain name
Certain names are taboo; for example, names that are already taken. Others that used to be off-limits have recently been allowed, such as combinations of top-level domains (edu.com4
) and domains that contain a repeating component (x.x.com5
).
Our advice in the second edition of this book was that names should be short and easy to type and that they should identify the organization that uses them. These days, the reality is that all the good, short names have been taken, at least in the com domain. It’s tempting to blame this state of affairs on squatters, but in fact most of the good names are in actual use.
RFC1032 recommends that the names of second-level domains be no longer than 12 characters, but DNS actually allows up to 63 characters in each component and up to 255 characters in a complete name. The 12-character suggestion is often ignored, and there is no real reason to adhere to it other than to relieve the tedium of typing longer names.
Domain bloat
DNS was designed to map an organization’s domain name to a name server for that organization. In that mode it needs to scale to the number of organizations in the world. Now that the Internet has become a conduit of mass culture, however, domain names are being applied to every product, movie, sporting event, English noun, etc. Domain names such as twinkies.com are not (directly) related to the company that makes the product; they’re simply being used as advertisements. It’s not clear that DNS can continue to scale in this way. The real problem here is that the DNS naming tree is an efficient data structure only when it has some hierarchy and is not totally flat. With each organization naming hundreds or thousands of products at the top level of the tree, hierarchy is doomed.
What we really need is a directory service that maps brand and marketing names to organizations, leaving DNS free to deal with IP addresses. The beginnings of this idea are implemented in most modern web browsers through a service provided by the RealNames Corporation. Unfortunately, RealNames is a proprietary monopoly; only organizations that subscribe and pay a fee can have their keywords listed in the database. Another possible solution is to enforce hierarchy in the system; for example, twinkies.hostess-foods.com. But this will never happen—we’ve already gone too far down the marketing-domain-name.com path.
Sony does things the right way from DNS’s perspective—all of its products are subdomains of sony.com. It might take an extra click or two to find the products you want, but DNS appreciates the hierarchy.
Registering a second-level domain name
To obtain a second-level domain name, you must apply to the authority for the appropriate top-level domain. ICANN is currently accrediting various agencies to be part of its shared registry project for registering names in the gTLDs. As of this writing, you have something like 25 choices of registrar, with about 80 others in various stages of the approval process. Check www.icann.org for the definitive list.
In Europe, contact the Council of European National Top-level Domain Registries at www.centr.org to identify your local registry and apply for a domain name. For the Asia-Pacific region, the appropriate body is the Asia-Pacific Network Information Center, www.apnic.net.
To complete the domain