Networking for Devs - DNS FAQ

As a senior developer, it’s clear some other technical staff lack a working knowledge of the Domain Name System.

Here’s an explainer, using the Cornell method - my favourite way to work through a subject quickly.

Cornell Method notes

What is DNS and a DNS query? Domain Name System is used to map human-friendly service names ('hosts') to the resource's numerical addresses (IP addresses) A DNS query and how it is resolved is the process of translating the human-friendly computer host names into IP addresses. DNS 'resolution' and 'translation' are the same thing.
How does a DNS query get resolved? When a user enters, the browser initiates a DNS resolver which sequences the query that ultimately leads to a translation. The recursive resolver function looks in cache 1. If not in cache, it goes to the first of the authoritative nameservers. This is hardcoded in the OS. For example `` 2. If translation not found, continue querying 3. Resolver -- queries --> internal cache 4. Resolver -- queries --> root nameserver 5. Resolver -- queries --> `.com` nameserver
What is the root nameserver? When a client begins to resolve a DNS query, the remote resolution process starts with a request to a root nameserver. It will respond with a referral to further authoritative servers. A root nameserver is a type of authoritative nameserver. Another type of authoritative nameserver is a **TLD nameserver**. For example, the request to translate `` will receive a response containing addresses of `.org` authoritative TLD server servers. Ao
How can performance be increased? The are DNS caching servers which store resolved mappings for a specified period. This reduces DNS traffic across the internet. How long cache entries are stored is according to the TTL value for the DNS record in question.
What are the various DNS records for? Besives translating names to IP addresses, DNS can instruct mail agents which is the best mail server to deliver email. An MX record provides a mapping between a domain a mail exchanges.
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