Domain Name System (DNS)
The Domain Name System (DNS) is a hierarchical and decentralized naming system for computers, services, or other resources connected to the Internet or a private network. It associates various information with domain names assigned to each of the participating entities. Most importantly, it translates human-readable domain names to the numerical IP addresses needed for locating and identifying computer services and devices with the underlying network protocols.
History
- The concept of DNS was introduced in 1983 with the publication of RFC 882 by Paul Mockapetris, which was later refined in 1987 with RFC 1034 and RFC 1035.
- Before DNS, hosts files were used for name resolution, but these became impractical as the Internet grew.
- The first implementation of DNS was the Berkeley Internet Name Domain (BIND) software, released in 1984 by the University of California, Berkeley.
How DNS Works
- Name Resolution: When a user types a domain name into a web browser, the DNS resolver sends a query to a DNS recursive resolver, which can be either the user's ISP or a public DNS service like Google Public DNS or Cloudflare DNS.
- Recursive DNS Server: This server attempts to find an answer by querying a DNS root name server, which directs the request to the appropriate top-level domain (TLD) server (e.g., .com, .org).
- TLD Server: The TLD server responds with the IP address of the authoritative DNS server for the specific domain in question.
- Authoritative Name Server: This server provides the final answer, which is the IP address for the domain name sought.
- Caching: DNS information is cached at various levels to improve performance, reducing the need for repeated DNS lookups.
Components of DNS
- Domain Name Space: A tree-like structure where each node is a domain name.
- Resource Records: These are the data types stored in DNS, including A records (IP addresses), MX records (mail exchanger), and TXT records (textual information).
- DNS Servers:
- Recursive DNS Servers
- Authoritative DNS Servers
- Root DNS Servers
- Zone Files: Text files that store the DNS database for a zone, including resource records.
Security Concerns
- DNS Spoofing: Also known as DNS cache poisoning, where DNS records are altered to redirect users to malicious sites.
- Distributed Denial of Service (DDoS): DNS can be targeted to disrupt services.
- DNSSEC: DNS Security Extensions add security to DNS by enabling authentication of DNS data, helping prevent DNS spoofing.
Recent Developments
- Encrypted DNS: Protocols like DNS over HTTPS (DoH) and DNS over TLS (DoT) are being adopted to encrypt DNS queries for privacy and security.
- IPv6: DNS has been extended to support IPv6 addresses through AAAA records.
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