WHAT IS DNS?
The Domain Name System (DNS) is a hierarchical decentralized naming system
for computers, services, or any resource connected to the Internet or a private
network. It associates various information with domain names assigned to each
of the participating entities.
Most prominently, it translates more readily memorized domain names to the
numerical IP addresses needed for the purpose of locating and identifying
computer services and devices with the underlying network protocols. By
providing a worldwide, distributed directory service, the Domain Name System is
an essential component of the functionality of the Internet.
The Domain Name System delegates the responsibility of assigning domain
names and mapping those names to Internet resources by designating
authoritative name servers for each domain. Network administrators may delegate
authority over sub-domains of their allocated name space to other name servers.
This mechanism provides distributed and fault tolerant service and was designed
to avoid a single large central database.
The Domain Name System also specifies the technical functionality of the
database service which is at its core. It defines the DNS protocol, a detailed
specification of the data structures and data communication exchanges used in
the DNS, as part of the Internet Protocol Suite. Historically, other directory
services preceding DNS were not scalable to large or global directories as they
were originally based on text files, prominently the HOSTS.TXT resolver. The
Domain Name System has been in use since the 1980s.
The Internet maintains two principal namespaces, the domain name hierarchy
and the Internet Protocol (IP) address spaces. The Domain Name System maintains
the domain name hierarchy and provides translation services between it and the
address spaces. Internet name servers and a communication protocol implement
the Domain Name System. A DNS name server is a server that stores the DNS
records for a domain; a DNS name server responds with answers to queries
against its database.
The most common types of records stored in the DNS database are for Start
of Authority (SOA), IP addresses (A and AAAA), SMTP mail exchangers (MX), name
servers (NS), pointers for reverse DNS lookups (PTR), and domain name aliases
(CNAME). Although not intended to be a general purpose database, DNS can store
records for other types of data for either automatic lookups, such as DNSSEC
records, or for human queries such as responsible person (RP) records. As a
general purpose database, the DNS has also been used in combating unsolicited
email (spam) by storing a real-time blackhole list. The DNS database is
traditionally stored in a structured zone file.
FUNCTION
An often-used analogy to explain the Domain Name System is that it serves
as the phone book for the Internet by translating human-friendly computer
hostnames into IP addresses. For example, the domain name www.example.com
translates to the addresses 93.184.216.119 (IPv4) and
2606:2800:220:6d:26bf:1447:1097:aa7 (IPv6). Unlike a phone book, DNS can be
quickly updated, allowing a service's location on the network to change without
affecting the end users, who continue to use the same host name.
Users take advantage of this when they use meaningful Uniform Resource
Locators (URLs), and e-mail addresses without having to know how the computer
actually locates the services.
Additionally, DNS reflects administrative partitioning. For zones operated
by a registry, also known as public suffix zones, administrative information is
often complemented by the registry's RDAP and WHOIS services. That data can be
used to gain insight on, and track responsibility for, a given host on the
Internet.
An important and ubiquitous function
of DNS is its central role in distributed Internet services such as cloud
services and content delivery networks.[6] When a user accesses a distributed
Internet service using a URL, the domain name of the URL is translated to the
IP address of a server that is proximal to the user.
The key functionality of DNS exploited here is that different users can
simultaneously receive different translations for the same domain name, a key
point of divergence from a traditional "phone book" view of DNS. This
process of using DNS to assign proximal servers to users is key to providing
faster response times on the Internet and is widely used by most major Internet
services today.
DOMAIN NAME SPACE
The domain name space consists of a tree data structure. Each node or leaf
in the tree has a label and zero or more resource records (RR), which hold
information associated with the domain name. The domain name itself consists of
the label, possibly concatenated with the name of its parent node on the right,
separated by a dot.
The tree sub-divides into zones beginning at the root zone. A DNS zone may
consist of only one domain, or may consist of many domains and sub-domains,
depending on the administrative choices of the zone manager. DNS can also be
partitioned according to class; the separate classes can be thought of as an
array of parallel namespace trees.
Administrative responsibility over any zone may be
divided by creating additional zones. Authority over the new zone is said to
be delegated to a designated name server. The parent zone
ceases to be authoritative for the new zone.
Thanks for Reading...
READ MORE:
- What is Troubleshooting Network?
- What is Web Server?
- What is Troubleshooting?
- What is Chat Room?
- What is IP Address?
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