Diff: Domain name system
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The Domain Name System (DNS) is a fundamental technology used on the internet to translate human-readable domain names into numerical IP addresses. This hierarchical and distributed naming system plays a crucial role in enabling users to access websites, send emails, and utilize various online services by simplifying the process of locating resources on the internet. |
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The '''Domain Name System''' ('''DNS''') is the distributed naming system used to translate domain names into information that network software can use. Its most familiar job is turning names such as example.com into IP addresses, but DNS is also used for mail routing, service discovery, domain delegation, and security-related records. |
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== Function and Operation == |
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DNS acts as a directory that converts user-friendly domain names (such as www.example.com) into IP addresses (such as 192.0.2.1) that computers and networking devices use to identify each other on the internet. This translation process occurs behind the scenes and is essential for ensuring that internet users can navigate the web without needing to memorize numeric IP addresses. |
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DNS is one of the core systems of the internet. It lets people use names instead of memorising numerical IP addresses, and it gives domain owners a way to publish technical records for their services. |
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=== DNS Hierarchy === |
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DNS is organized in a hierarchical structure, consisting of several levels, each serving a specific purpose: |
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== Purpose == |
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Computers communicate using addresses, not human-friendly names. A web browser can show a name such as www.example.com, but the network connection needs an IP address. DNS provides the lookup system that connects the name to the relevant record. |
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* Root Domain: At the top of the hierarchy is the root domain (represented by a dot), which is managed by a group of authoritative root servers. These servers provide information about top-level domains (TLDs). |
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* Top-Level Domains (TLDs): TLDs are the next level in the hierarchy and include generic TLDs (gTLDs) like .com, .org, .net, as well as country-code TLDs (ccTLDs) like .uk, .jp, and .br. |
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* Second-Level Domains: Below TLDs are second-level domains (SLDs), such as "example" in www.example.com. These are registered by individuals or organizations. |
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* Subdomains: Subdomains can be further created, forming a more detailed hierarchy (e.g., sub.example.com). |
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DNS is not only a web system. Email servers use DNS records to find where mail for a domain should be delivered. Security systems use DNS records for sender authentication, certificate checks, and other validation. Many applications use DNS to find services and endpoints. |
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=== DNS Resolution Process === |
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When a user enters a domain name in a web browser, the DNS resolution process occurs: |
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== Structure == |
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DNS is hierarchical. At the top is the root. Below the root are top-level domains such as .com, .net, .org, .uk, and many others. Below those are registered domain names, then any subdomains created by the domain holder. |
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# Local Resolver: The user's device sends a query to a local DNS resolver, usually provided by their internet service provider (ISP). |
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# Recursive Query: If the local resolver doesn't have the IP address in its cache, it initiates a recursive query to find the authoritative name server responsible for the domain. |
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# Authoritative Name Server: The authoritative name server holds the specific IP address associated with the domain and responds with the IP address. |
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# Response: The local resolver receives the IP address and caches it for future use. The user's device then uses the IP address to establish a connection to the desired website or service. |
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A full domain name is made from labels. In www.example.com, the labels are www, example, and com. The hierarchy is read from right to left: com is the top-level domain, example is registered under it, and www is a host or subdomain label under example.com. |
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== DNS Security and Challenges == |
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While DNS is a critical component of the internet, it is not immune to security challenges: |
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== Resolution == |
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When a device needs a DNS answer, it usually asks a recursive resolver. That resolver may already have a cached answer. If not, it works through the hierarchy: |
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* DNS Spoofing: Malicious actors can manipulate DNS responses to redirect users to fraudulent websites. |
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* DDoS Attacks: Distributed Denial of Service (DDoS) attacks can overwhelm DNS servers, disrupting access to websites. |
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* DNSSEC: DNS Security Extensions (DNSSEC) is a protocol that helps mitigate these risks by adding a layer of cryptographic authentication to DNS responses. |
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* It asks the root servers where to find the top-level domain servers. |
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* It asks the top-level domain servers where to find the authoritative servers for the domain. |
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* It asks the authoritative servers for the record being requested. |
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* It returns the answer to the client and may cache it for a limited time. |
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== Future Developments == |
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DNS continues to evolve to meet the changing needs of the internet. New TLDs, such as .app and .blog, have been introduced, expanding the namespace. Efforts to improve DNS privacy, enhance security, and ensure global accessibility remain ongoing. |
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Caching reduces load and improves speed. The time-to-live value on a DNS record tells resolvers how long they may keep an answer before checking again. |
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== Resource Records == |
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DNS stores different types of resource records. Common examples include: |
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* A records, which map a name to an IPv4 address. |
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* AAAA records, which map a name to an IPv6 address. |
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* CNAME records, which make one name an alias of another. |
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* MX records, which identify mail servers for a domain. |
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* NS records, which identify authoritative name servers. |
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* TXT records, which store text used for policies and verification. |
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* SOA records, which describe authority and timing information for a zone. |
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== Root and Authority == |
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The DNS root zone is managed through a formal coordination process. ICANN explains DNS as a system that helps users navigate the internet by allowing text-based names to be used instead of IP addresses. IANA maintains root-zone information and other technical registries used by internet infrastructure. |
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Domain owners do not usually manage the whole hierarchy. A registrar handles the registration of a domain name, a registry operates a top-level domain, and authoritative DNS providers publish records for the domain. |
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== Security == |
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DNS was originally designed for function and resilience rather than modern hostile networks. Attacks can include cache poisoning, hijacked domain accounts, malicious redirects, domain abuse, and denial-of-service attacks against DNS infrastructure. |
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DNSSEC adds cryptographic signing to DNS data so resolvers can check whether an answer is authentic. DNSSEC does not encrypt ordinary DNS queries by itself, but it helps protect against forged answers when correctly deployed. |
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Privacy has also become more important. Traditional DNS queries can reveal browsing and service-lookup behaviour to networks and resolvers. Newer approaches such as encrypted DNS transports are intended to reduce that exposure, although they also raise operational and policy questions. |
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== See Also == |
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* [[Internet Corporation for Assigned Names and Numbers (ICANN)]] |
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* [[Cloud Computing]] |
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* [[Data Centre]] |
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== References == |
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* [https://www.icann.org/resources/pages/dns-2022-09-13-en ICANN: The Domain Name System] |
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* [https://www.rfc-editor.org/info/rfc1034 RFC 1034: Domain names, concepts and facilities] |
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* [https://www.rfc-editor.org/info/rfc1035 RFC 1035: Domain names, implementation and specification] |
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* [https://www.iana.org/domains/root IANA: Root Zone Database] |
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[[Category:Internet]] |
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[[Category:Networking]] |
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[[Category:Computing]] |