OBTAIN AN IP ADDRESS BY USING DHCPBEFORE YOU BEGIN THIS EXERCISE, YOU...

13-29Lesson 2 Understanding the Domain Name System

Domain-Naming Guidelines

When you create a domain namespace, consider the following domain guidelines and

standard naming conventions:

■

Limit the number of domain levels. Typically, DNS host entries should be three or

four levels down the DNS hierarchy and no more than five levels down the hier-

archy. The numbers of levels increase the administrative tasks.

■

Use unique names. Each subdomain must have a unique name within its parent

domain to ensure that the name is unique throughout the DNS namespace.

■

Use simple names. Simple and precise domain names are easier for users to

remember. They also enable users to search intuitively and locate Web sites or

other computers on the Internet or an intranet.

■

Avoid lengthy domain names. Domain names can be up to 63 characters, includ-

ing periods. The total length of an FQDN cannot exceed 255 characters. Case-

sensitive naming is not supported.

■

Use standard DNS characters and Unicode characters.

■

Windows 2000 Server and Windows Server 2003 support the following standard

DNS characters: a–z, 0–9, and the hyphen (-), as defined in RFC 1035.

■

The DNS Service also supports the Unicode character set. The Unicode character

set includes additional characters not found in the American Standard Code for

Information Interchange (ASCII) character set; these additional characters are

required for languages such as French, German, and Spanish.

Note Use Unicode characters only if all servers running the DNS Service in your environ-ment support Unicode. For more information about the Unicode character set, read RFC 2044 by searching for “RFC 2044” with your Web browser.

What Are Zones?

A zone represents a discrete portion of the domain namespace. Zones provide a way

to partition the domain namespace into manageable sections, and they provide the fol-

lowing functions:

■

Multiple zones in a domain namespace are used to distribute administrative tasks

to different groups. For example, Figure 13-9 depicts the microsoft.com domain

namespace divided into two zones. These zones allow one administrator to man-

age the microsoft and sales domains, and another administrator to manage the

development domain.

■

A zone must encompass a contiguous domain namespace. For example, in Fig-

ure 13-9, you cannot create a zone that consists of only the sales.microsoft.com

and development.microsoft.com domains because these two domains are not

contiguous.

Note For more information about contiguous namespaces, see Chapter 14.comZone2Zone1 databasefilemicrosoftdevelopmentsalesZone1

F13us10

Figure 13-9 A domain namespace is divided into zones.

The name-to-IP address mappings for a zone are stored in the zone database file. Each

zone is anchored to a specific domain, referred to as the zone’s root domain. The zone

database file does not necessarily contain information for all subdomains of the zone’s

root domain, only those subdomains within the zone.

In Figure 13-9, the root domain for Zone1 is microsoft.com, and its zone file contains

the name-to-IP address mappings for the microsoft and sales domains. The root

domain for Zone2 is development, and its zone file contains the name-to-IP address

mappings only for the development domain. The zone file for Zone1 does not contain

the name-to-IP address mappings for the development domain, although development

is a subdomain of the microsoft domain.

What Are Name Servers?

A DNS name server stores the zone database file. Name servers can store data for one

zone or multiple zones. A name server is said to have authority for the domain name

space that the zone encompasses.

One name server contains the master zone database file, referred to as the primary

zone database file, for the specified zone. As a result, there must be at least one name

server for a zone. Changes to a zone, such as adding domains or hosts, are performed

on the server that contains the primary zone database file.