(DNS) Domains Name System

# Learning Materials

- DNS

- Domain Hierarchy

- Record Types

- DNS workflow

$DNS (Domain Name System)

DNS (Domain Name System) provides a simple way for us to communicate with devices on the internet without remembering complex numbers.much like phonebook of the Internet, Humans access information online through domain names, like nytimes.com or espn.com.

DNS using domain to lookup unique IP server. every computer on the internet has its own unique address to communicate with it called an IP address. An IP address looks like the following 104.26.10.229, 4 sets of digits ranging from 0 - 255 separated by a period. When users want to visit a website, domain will lookup to IP server of website.

$Domain Hierarchy

The DNS hierarchy, also called the domain name space, is an inverted tree structure. The DNS hierarchy tree has a single domain at the top of the structure called the root domain – indicated by the “.” as we have mentioned above. Below the root domain are the top-level domains that divide the DNS hierarchy into segments containing second-level domains, sub-domains, and hosts.

TLD (Top-Level Domain)

A top-level domain (TLD) is the part of a domain name that appears after the final dot in the domain name.

There are many different top-level domains, including:

.com (commercial organizations)

.net (internet service providers or infrastructure)

.org (non-profit organizations)

.gov (government agencies)

.edu (educational institutions)

Second-Level Domain

A second-level domain is the part of a domain name that appears before the top-level domain for example hashnode.com. When registering a domain name, the second-level domain is limited to 63 characters + the TLD and can only use a-z 0-9.

Subdomain

A subdomain is a domain that is part of a larger domain. It is created by adding a prefix to the main domain name. For example, if the main domain is "example.com," a subdomain might be "mail.example.com" or "blog.example.com.". Subdomains are a useful way to organize and structure a website, and they can also be used to customize URLs for specific purposes.

$Record Types

There are several different types of DNS records that can be used to store information about domain names and IP addresses. These records are stored in a DNS database, which is a distributed database that is used to store information about domain names and their associated IP addresses.

DNS record types :

• A (Address) record: An A record maps a domain name to an IP address. It is used to direct traffic to a specific website or other online resource.

• CNAME (Canonical Name) record: A CNAME record maps a domain name to another domain name. It is used to create aliases for a domain name, so that multiple names can be used to access the same website or other online resource.

• MX (Mail Exchange) record: An MX record maps a domain name to a mail server. It is used to route email to the correct mail server for a specific domain.

• NS (Name Server) record: An NS record specifies the name servers for a domain. It is used to delegate control of a domain to specific name servers.

• TXT (Text) record: A TXT record is used to store text-based information in a DNS database. It can be used to store a variety of information, such as SPF records (used to prevent email spoofing) and domain ownership information.

$DNS Workflow

DNS has several stages in its work :

1. Client Domain name lookup : Client request domain on browser, computer will send request to local dns cache.

2. Recursive/resolve DNS Server : DNS resolver will check cache dns on local database resolved DNS server. if domain found, the DNS resolver will response lookup domain client.

3. Root Servers: if domain not found on resolve server, DNS lookup will continue lookup request to root server. root server stored top-level-domains such as .com .net .org

4. Authoritative name server lookup : resolver will then send a request to the authoritative name server, which is a server that is responsible for managing the DNS records for a specific domain.

5. Authoritative Server response Domain : The authoritative name server will respond with the IP address associated with the domain name being looked up. request returned to the computer that made the original request, and the computer can then use the IP address to connect to the server

Referensi

\> https://www.cloudflare.com/learning/dns/what-is-dns/

\> https://en.wikipedia.org/wiki/Domain_Name_System

\> https://tryhackme.com/room/dnsindetail

\> https://cloudinfrastructureservices.co.uk/what-is-dns-hierarchy

\> https://cloudacademy.com/blog/how-dns-works/