DNS study notes — Name resolution

Photo by David Mazeau on Unsplash

Introduction

  • Name resolution overview and history
  • Domain

What exactly is name resolution?

  • You don’t have to remember your IP address.
  • If only the domain name is fixed, it is not necessary to inform the user when the IP address is changed.

One of the name resolutions is DNS (Domain Name System). The simple mechanism of DNS is that the client inquires about the database that corresponds to the IP address and domain name .

Non-DNS name resolution

Hosts file

Problems with name resolution by Hosts file

  • It is difficult to ensure that every host on the network has the latest Hosts file.
  • The number of hosts increases, the Hosts file grows, and traffic increases.

Name resolution by DNS

Domain namespace

  • root is the root domain
  • node is the domain name
  • leaf (terminal node) is the host name

The tree structure makes it possible to find all hosts by tracing from root. The DNS tree is called the Domain Name Space . A domain is subject to DNS only after the domain name is registered in the domain namespace. Nodes under a domain cannot have the same name in the same hierarchy. In other words, the domain namespace needs to be managed in the same hierarchy so that domain names are not duplicated.

Domain management

TLD and SLD

  • Country Code TLD, ccTLD (2-letter TLD that can only be used by domestic organizations, with the exception of the United States)
  • Generic Code TLD, gTLD ( TLD with 3 or more characters that can be used regardless of the country to which you belong)
  • Only in the United States, you can use a TLD of 3 or more letters, which means the form of an organization.

The domain directly under the TLD is called the Second Level Domain (SLD) and represents the attributes of the organization .

FQDN

Source: https://giphy.com/

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Maciej

DevOps Consultant. I’m strongly focused on automation, security, and reliability.