DNS (Domain Name System)

06 Apr 2021 in System Network

This page will be kept updated.

• People type Domain name to access to the server, but IP address is what computer needs when they request/send data.

• Therefore, DNS should be converted into IP address. It is not too simple, because computers cannot have tons of DNS-IP matching info in their memory. They request DNS server to get IP info.

• For example, google.com , There is invisible . at the end of ‘com’, so it is google.com.

  • . is root domain and it is usually hidden

  • DNS is needed to be interpret backwards.

    • . => com => google
    • It has a tree structure.

    

How is it propagated around internet?

• Domain name has a tree structure.

  • From the top, Root => Top-level DN => Second level DN => SubDN

    생활코딩 WEB-2 Domain Name System

    

• Types of DNS Server

  1. DNS recursive resolver : It is served by ISP(Internet Service Provider)
  2. Root name server
  3. Top Level Domain/ TLD name server
  4. Authoritative name server

  

  생활코딩 WEB-2 Domain Name System

YT Source : TechTerms - DNS explained

• ex) When we type ‘google.com’,

  ​ => It is automatically converted into ‘google.com.’ , Dot at the end!

  ​ => It goes to ‘.’ Root server. It has IP info of ‘com, net, org…’.

  ​ https://root-servers.org/

  • If it is google.com. then in this step, It will return the IP of .com TLD Name server.

  • And then , TLD IP address returns to the computer, and computer again sends request to look for google.

  • This process repeats until It hits Authoritative name server(?) and return the IP address.

DNS records

How to add DNS entries to a DNS server?

https://docs.microsoft.com/en-us/windows-server/networking/technologies/ipam/add-a-dns-resource-record

ipconfig /displydns
ipconfig /flashdns

Host file location

C:\Windows\System32\drivers\etc\hosts

• In the past, People override their hosts file with Standford Research Institute.
• Stanford Research Institute has all the match info of Domain Name and IP
  • New records were manually added by people.
  • It took too long to update all.
  • People had to update their hosts file constantly to gain new info.
  • during operation time..

DNS principles

• As soon as the computer is connected to lan/wifi, It sets the domain name system server automatically by DHCP.

• When you type address, then It will look up hosts file first (Cache is also written here!) if there is no matching info found, then It will send traffic to DNS server.

  

  Control Panel > Network and Internet > Network Connection > Wi-Fi or Ethernet > Properties > IPv4

nslookup yejip.com
nslookup -type=a yejip.com
the same

DNS Zone

https://www.youtube.com/watch?v=f7bmOXCpkrg