Configuring DNS for Active Directory - MCTS Guide to Microsoft Windows Server 2008 Active Directory Configuration - page 390

Figure 9-25

Viewing counters in Performance Monitor

You should sample some key DNS counters periodically when DNS is performing well
because this information is useful for troubleshooting. In Performance Monitor, you can view
performance in real time or save the data to a log to be viewed later. You can save logs of key
counters for which you have collected data during peak and off-peak hours. These saved logs
constitute your baseline for DNS performance. Later, if DNS performance is degrading, you can
compare baseline logs to current data to see which counters differ significantly, allowing you to
pinpoint the bottleneck. Because queries and dynamic updates are among the most frequent
tasks a server handles, these two counters should be included in your baseline logs: Total Query
Received/sec and Dynamic Update Received/sec.

Chapter Summary

DNS is based on a hierarchical naming structure and a distributed database. DNS names
use the structure host . domain . top-level-domain or perhaps host . subdomain . domain . top-
level-domain . This name is referred to as the fully qualified domain name (FQDN).

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DNS can be described as an inverted tree with the root domain at the top, TLDs branch-
ing off the root, and domains and subdomains branching off TLDs. The entire DNS tree is
called the DNS namespace. Every domain has one or more authoritative name servers.

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The DNS database is composed of zones containing resource records, such as Start of
Authority (SOA), Host (A), and Service (SRV) records. Host (A) resource records can be
updated with static or dynamic updates.

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DNS lookups involve iterative and recursive queries. Most lookups start from the DNS
resolver with a recursive query to a DNS server. The DNS server satisfies the query or per-
forms a series of iterative queries, starting with a root server.

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DNS servers can perform one or more of the following roles: authoritative server, for-
warder, conditional forwarder, and caching-only server. DNS databases consist of the

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