DNS stands for Domain Name System and converts website names to IP addresses. Without DNS servers, web browsing would be almost impossible and every device connected to the internet requires one in order to load websites properly.
Elizabeth Feinler at Stanford Research Institute kept a list of computers connected to the internet during the 1970s and 80s. As this task became too burdensome for her to maintain, Paul Mockapetris created DNS in 1983 as an automated, scalable system for domain name-to-IP address translation.
Domain names
Domain names are unique addresses used to access websites on the internet. When entering this name in a browser URL bar, visitors are taken directly to that site. While many use “domain” and “website” interchangeably, technically speaking they’re different entities – a domain is like the address for a home, while website content exists at that location.
The Domain Name System (DNS) is a global database that converts human-readable domain names to machine-readable IP addresses through resolving. When users type a domain name into their browser, this database searches to find its IP address before translating this address into its web server’s IP address, thus loading onto computers.
Domain names can contain up to 63 characters. In addition, they can include top-level domains and paths – subdomains which direct visitors towards specific pages within a website.
When choosing a domain name for your business, several factors should be taken into consideration when selecting one. First and foremost, make sure it’s short and memorable; also include keywords people might search for online; as well as one which has been registered long enough so it will have more authority with search engines.
A domain name can consist of various components that each have specific functions. For instance, subdomains are commonly used to host blogs or email accounts while there are records that allow administrators to manage how a domain name routes; one such record is called the CNAME record which allows redirects for emails or pages.
Zones
A DNS zone is an entity within the domain namespace that contains settings and records related to DNS settings and services, including redirections between domain names and IP addresses, service details information display, verification/authentication purposes as well as verification/authentication verification/authentication services. A domain can belong to multiple zones while each can expand into subdomains allowing one entity to control multiple domains simultaneously.
Zone configurations are rules that define how traffic for a particular domain should be routed. A properly constructed configuration can enhance performance, minimize network outages and protect data loss while offering greater flexibility for new services like websites or email servers to be deployed quickly and seamlessly.
Management of the DNS system is divided into distinct zones, each overseen by a different organization or person, to maximize efficiency. Each zone has a unique name and contains various DNS records – one being an SOA record that specifies a primary DNS server and administrator email address as well as various NS records such as A and AAAA ones, CNAME records, and MX records.
Zones are essential to businesses, directing internet traffic to websites, application servers and email services. Zones also protect companies against cyber attacks by implementing appropriate security policies to ensure malware does not gain entry to one zone and spread freely within their networks; by monitoring DNS zone changes companies can quickly detect any unauthorized changes that might arise and stop any further disruption from taking place.
Caching
Caching is the practice of temporarily storing data closer to users for easier access and loading of that information. Browsers frequently visited by their users will cache images and elements on websites they regularly access in order to make loading them faster than if each time the user had to download from their server each time they needed the data. Operating systems also employ caching technologies which save resources by accessing local servers rather than having to query external ones for information.
A DNS resolver acts as an intermediary between users and servers they wish to visit, taking queries from a DNS client and searching for an IP address. Furthermore, it can cache DNS lookups before returning them directly to their original source – thus decreasing time needed for domain name resolution.
When a DNS query is submitted to a resolver, it first checks its own cache for an answer before querying a recursive server to see if they can help – this server will then query both root and TLD servers as necessary; alternatively, nonrecursive queries may also be used which bypass these intermediary servers and go directly to an authoritative server.
The DNS resolution process includes four servers working together to deliver IP addresses to their client: recursive servers, root nameservers, TLD nameservers and authoritative servers. Recursive servers act as intermediary servers between DNS client and server: they take queries from clients and provide the answer from cache; or pass them on to another recursive resolver server that may contain it.
Recursive queries
Recursive queries are an effective tool for managing hierarchical data. Recursion queries use a special syntax that enables recursion; however, their execution can be costly due to performance impacts in large hierarchies or structures with deep nests; therefore it should only be used sparingly so as not to negatively impact performance.
For a recursive query to work successfully, first create a common table expression (CTE) with two components – anchor member and recursive member. Anchor members determine the starting point and base result set of any recursion; while recursive members reference CTE and return subresult sets until an exit condition has been met; these sub-result sets can then be unioned using UNION ALL operator.
Recursive queries are SQL statements that repeatedly iterate until a specified termination criteria has been met and produce new rows or records based on results of previous iterations(s). They are commonly used with hierarchical data sources like organizational charts or file systems.
Example Recursive Queries The following is an example of recursive query which begins with an anchor query to select all employees whose boss_id equals NULL in the employee table, including Roxanna Fairlie. From here, recursion begins – finding Frank’s parents before continuing its way up the hierarchy until reaching its root point.
In this example, the recursive query is a straightforward SELECT statement which takes advantage of the hierarchical structure of the employee table to return all employees who report directly to Frank, along with their parents, plus total amounts invested by each investor based on investors_number field values.
Authoritative servers
Authoritative servers serve as the authoritative source of DNS information for domains. They host official DNS records and monitor their accuracy while also offering high-performance and secure DNS services to enterprise customers requiring these services for seamless Internet browsing experiences.
When someone visits a website using their browser, the browser sends a request to a DNS resolver asking for its IP address. This DNS resolver uses cached information or, if none can be found in its cache, will go through a recursive process asking other servers until one provides an answer; at which time it then provides it back to the person viewing the site.
Authoritative servers are domain-specific DNS servers that contain the original zone file for their domains, with specific configurations that make them different from other name servers. Authoritative servers must respond only to domain queries that match those registered in their system; additionally, authoritative servers act as final destination of non-cached queries when necessary.
Primary name servers are authoritative servers configured to respond to queries for specific zones. While no formal delegation exists for them to serve this role, there’s nothing stopping a DNS administrator from configuring their server as authoritative for zones for which they don’t yet hold authority.
BIND and ISC are two different DNS server software options. BIND is widely utilized and most authoritative servers utilize this software, while ISC offers more specialized features geared towards enterprise applications. Both servers may become compromised due to security defects; whenever any such vulnerability is identified in any one of them, ISC issues a security advisory notifying all concerned server types that they could be vulnerable.