What is DNS; Why DNS is Important<\/h2>\n
DNS is like a phonebook for websites. It translates common names like example.com<\/em> into IP addresses so computers can load remote resources. It prevents us from having to remember numbers like 93.184.216.34<\/em> (IPV4) or\u2014even worse\u2014something like 2606:2800:220:1:248:1893:25c8:1946<\/em> (IPV6). This keeps things human-readable at a high level but allows for easy translation into machine-readable formats for efficiency.<\/p>\n Every device connected to the Internet has a unique IP address assigned so other devices can find it. In this way, IP addresses are like physical addresses. When you type example.com<\/em> into your web browser, the first request is to a DNS server to translate that human-readable name into an actual IP address. Only then can your browser connect to the example.com web server and load the page.<\/p>\n A more technical description of DNS is as follows:<\/p>\n That’s just for us geeks out there. The general takeaways are that DNS allows one computer to find another and that it uses a pretty complex network of other computers to do so. This complicated process is known as DNS resolution<\/strong> or DNS lookup<\/strong>.<\/p>\n DNS can be thought of as the internet’s directory service. It’s utilized by a wide range of applications including email clients, FTP clients, and\u00a0especially<\/em> web browsers. Each of these uses a DNS lookup protocol to translate common hostnames into IP addresses that can be used by network routers to facilitate TCP\/IP connections. The basic protocol of DNS Lookup is outlined here:<\/p>\n DNS is designed to be a “black box service” such that consumer applications like email, video games, and web browsers can make a single network request and receive a single network response. Behind the scene, however, the process is much more complex and involves several distinct phases of DNS resolution.<\/p>\n [alert type=yellow ]Summary<\/strong>: DNS “resolves” hostnames into IP addresses.[\/alert]<\/p>\n DNS itself is an application-layer service meaning it provides utility to software applications of all types. This includes operating systems, email clients, web browsers, and even video games. When a piece of software needs to find an IP address for a hostname\u2014it uses DNS services.<\/p>\n Most web-based applications use Transmission Control Protocol (TCP)<\/strong> for communication between servers. TCP offers reliability, among other services, that is preferable for things like web streaming, loading websites, and even transmitting login credentials. However, TCP requires a bit more work on the backend to facilitate these services.<\/p>\n For this reason, DNS relies on another protocol named User Datagram Protocol (UDP)<\/strong> which runs on port 53. In a nutshell, UDP reduces the number of times that DNS servers have to communicate back-and-forth so data transmission can begin more quickly. Keep in mind, before a webpage can start<\/em> to load\u2014DNS has to be resolved.<\/p>\n Hostname Aliasing<\/strong> – Allows one hostname to represent another. For example, www.example.com could be an\u00a0alias<\/em> for example.com In this case, example.com is considered the canonical hostname<\/em>.<\/p>\n MailServer Aliasing<\/strong> – Mailserver aliasing is similar to hostnames but differs in that it’s email specific. This allows email addresses such as bob@12.us-relay-west-7.example.com to be simplified to bob@example.com.<\/p>\n Load Distribution\/Balancing<\/strong>– Modern websites are often replicated on several servers such that many IP addresses are associated with the same canonical hostname. Load balancing selects from a list of IP addresses when responding to DNS queries as a means of distributing client requests across several different servers.<\/p>\n [alert type=yellow ]Summary<\/strong>: DNS relies on UDP protocols to minimize network requests and offers several services to help distribute requests to simplify network structure.[\/alert]<\/p>\n Internet Service Providers (ISPs) provide local DNS servers for their customers that store records of common hosts. For example, your ISP\u00a0absolutely<\/em> knows the IP address for google.com. ISPs cache DNS records for hostnames to help reduce the time their customers have to wait to connect to websites and other remote hosts.<\/p>\n What happens when new websites are queried? What about when a website\u00a0changes<\/em> its IP address? These are cases where local DNS servers don’t have the required information for customer applications. In these situations, local DNS servers must then go out onto the DNS server network to find the IP address. This can be a complex process and involves several steps.<\/p>\n DNS queries originate from the Application layer and, regardless of the depth of traversal on the DNS server network, ultimately end up on the Application layer of each successive DNS server. The process can become complex based on network design but involves the following stages.<\/p>\n [alert type=yellow ]Summary<\/strong>: DNS Servers are on a global, distributed, complex network.[\/alert]<\/p>\n DNS lookup requests originate from a wide range of applications including email, web-browsers, and even video games. Using local DNS resolver<\/strong> services, applications are able to make simple DNS hostname requests and not have to worry about the complexity. DNS resolvers typically communicate directly with local ISP DNS servers but applications can easily be configured to use 3rd party services such as Cloudflare’s 1.1.1.1<\/a> instead.<\/p>\n The first step in DNS resolution is through a client’s ISP via UDP on port 53. The request is passed to the local DNS server. Local DNS servers cache hostname\/IP translations and, if the DNS record already exists and has not expired, the local DNS server can immediately provide the IP mapping for the queried hostname. Otherwise, the local DNS must venture onto the DNS network for updated information.<\/p>\n Root servers are the most authoritative servers on the DNS network. Currently, there are 13 root DNS servers located around the world hosted by entities such as Verisign, Inc., Cogent Communications, NASA, and the US Department of Defense (R<\/a>).<\/p>\n The Root DNS servers are tasked with maintaining a database of Top-Level Domain (TLD) mappings that include things like .com, .net, .org, .gov, and even country-specific mappings like .us, .co.uk, and .zm. These mappings direct DNS hostname queries to the DNS servers responsible for finding host\/IP mappings specific to a given TLD (R<\/a>).<\/p>\n The Internet Address Name Association (IANA) is responsible for maintaining a publicly-viewable record of Root DNS records. Using their database, one can quickly find the mappings between TLDs and nameservers. For example, the .com TLD has the following information:<\/p>\n Sponsoring Organization<\/strong><\/p>\n VeriSign Global Registry Services<\/em><\/p>\n 12061 Bluemont Way Name Servers<\/strong><\/p>\n\n
DNS Services<\/h2>\n
![\"dns](\"https:\/\/www.alpharithms.com\/wp-content\/uploads\/88\/dns-services-listing.jpg\" "\\"dns-services-listing\\"")
\n
Application-Level Services<\/h3>\n
DNS Servers<\/h2>\n
![\"types](\"https:\/\/www.alpharithms.com\/wp-content\/uploads\/88\/types-of-dns-servers.jpg\" "\\"types-of-dns-servers\\"")
DNS Resolvers<\/h3>\n
Local DNS Servers<\/h3>\n
Root DNS Servers<\/h3>\n
\nReston Virginia 20190
\nUnited States<\/p>\n