Domain Name System for internet address translation
Core Idea: DNS (Domain Name System) is the decentralized naming system that translates human-readable domain names into machine-readable IP addresses, functioning as the internet's phonebook.
Key Elements
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Key principles
- Hierarchical and distributed database
- Domain name space organized as an inverted tree
- Delegated administration across organizations
- Caching at multiple levels for performance
- Redundancy through multiple nameservers
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DNS resolution process
- User enters domain name in browser
- Operating system checks local cache
- Request sent to recursive resolver (usually ISP)
- Resolver navigates DNS hierarchy if needed:
- Root nameservers
- Top-level domain (TLD) nameservers
- Authoritative nameservers
- IP address returned to client
- Connection established with web server
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Common record types
- A: Maps hostname to IPv4 address
- AAAA: Maps hostname to IPv6 address
- CNAME: Creates an alias from one domain to another
- MX: Specifies mail exchange servers
- TXT: Stores text information (verification, SPF, etc.)
- NS: Delegates a DNS zone to use given authoritative nameservers
- SOA: Specifies authoritative information about a DNS zone
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DNS propagation
- Time required for changes to spread through DNS caches
- Controlled by TTL (Time To Live) values
- Can take minutes to days depending on settings
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Common DNS issues
- NXDOMAIN: Domain name does not exist
- DNS poisoning/spoofing: Corrupted DNS data
- Slow resolution: Misconfigured or overloaded nameservers
- Split-horizon DNS: Different answers based on query source
Additional Connections
- Broader Context: Internet Protocol Suite (DNS operates alongside TCP/IP)
- Applications: DNS for Web Developers (practical domain configuration)
- See Also: DNSSEC (security extensions for DNS authentication)
References
- RFC 1034 - Domain Names - Concepts and Facilities: https://tools.ietf.org/html/rfc1034
- DNS Security Extensions: https://www.icann.org/resources/pages/dnssec-what-is-it-why-important-2019-03-05-en
#dns #networking #internet-infrastructure
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