domain name system
(DNS)
The domain name system
(DNS) is the way that internet domain
names are located and translated into internet
protocol (IP) addresses. The domain
name system maps the name people use to locate a website to the IPaddress that a computer uses to locate a
website. For example, if someone types TechTarget.com into a web browser, a
server behind the scenes will map that name to the IP address 206.19.49.149.
Web browsing and most other internet activity rely on DNS to
quickly provide the information necessary to connect users to remote hosts. DNS
mapping is distributed throughout the internet in a hierarchy of
authority. Access providers and enterprises, as well as governments, universities and
other organizations, typically have their own assigned ranges of IP addresses
and an assigned domain name; they also typically run DNS servers to manage the
mapping of those names to those addresses. Most URLs are built around the
domain name of the web server that takes client requests. For example,
the URL for this page is http://searchnetworking. techtarget.com/definition/domain-name-system.
How does DNS work?
DNS
servers answer questions from both inside and outside their own domains. When a
server receives a request from outside the domain for information about a name
or address inside the domain, it provides the authoritative answer. When a
server receives a request from inside its own domain for information about a
name or address outside that domain, it passes the request out to another
server -- usually one managed by its internet service provider. If that server does not know the answer or the authoritative
source for the answer, it will reach out to the DNS servers for the top-level
domain -- e.g., for all of .com or .edu. Then, it will pass the request down to
the authoritative server for the specific domain -- e.g., techtarget.com or
stkate.edu; the answer flows back along the same path.
How does DNS increase web
performance?
To
promote efficiency, servers can cache the answers they receive for a set amount
of time. This allows them to respond more quickly the next time a request for
the same lookup comes in. For example, if everyone in an office needs to access
the same training video on a particular website on the same day, the local DNS
server will ordinarily only have to resolve the name once, and then it can
serve all the other requests out of its cache. The length of time the record is
held -- the time to live is configurable; longer values
decrease the load on servers, shorter values ensure the most accurate
responses.
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