DNSとインフラ

DNS（ドメインネームシステム）

Hierarchical naming system that translates domain names into IP addresses.

ネームサーバー

Server that stores DNS records and responds to DNS queries for a domain zone.

Aレコード

DNS record mapping a domain name to an IPv4 address.

AAAAレコード

DNS record mapping a domain name to an IPv6 address.

CNAMEレコード

DNS record that creates an alias from one domain name to another canonical name.

MXレコード

DNS record specifying the mail server responsible for receiving email for a domain.

TXTレコード

DNS record holding arbitrary text data, commonly used for email authentication and domain verification.

NSレコード

DNS record that delegates a DNS zone to an authoritative nameserver.

DNSリゾルバー

Software or service that performs recursive DNS lookups on behalf of clients.

DNSキャッシュ（TTL）

Temporary storage of DNS query results with a Time-To-Live expiration.

権威DNSサーバー

Server that holds the original DNS records for a zone and provides definitive answers.

DNSゾーンファイル

Text file describing a DNS zone with records for all domains in that zone.

SOAレコード

Start of Authority record containing administrative information about a DNS zone.

サブドメイン

Domain that is part of a larger domain, created by prepending a label (e.g., blog.example.com).

IPアドレス

Numerical label (IPv4 or IPv6) assigned to each device connected to a computer network.

再帰DNSリゾルバ

Server that performs the full DNS resolution chain on behalf of clients and caches results.

DNSルートサーバー

Top-level nameservers that direct resolvers to the correct TLD nameservers.

DNSゾーン

Administrative partition of the DNS namespace managed by a single authoritative authority.

PTRレコード（逆引きDNS）

DNS record that maps an IP address back to a hostname for reverse DNS lookups.

DNSデリゲーション

Transfer of DNS authority for a child zone to designated nameservers via NS records.

DNSラウンドロビン

Load-balancing technique using multiple IP addresses on a single hostname to distribute traffic.

DNSシンクホール

DNS configuration that redirects malicious domains to a controlled IP to block or analyze threats.

EDNS（DNSの拡張メカニズム）

RFC 6891 extension to the DNS protocol enabling larger messages, DNSSEC, and new option codes.

DNS増幅攻撃

DDoS technique exploiting open DNS resolvers to flood a victim with amplified response traffic.

ネガティブキャッシュ（NXDOMAIN）

Caching of NXDOMAIN and NODATA DNS responses to prevent repeated queries for non-existent names.