DNS in details

What is DNS?

The Domain Name System (DNS) helps us humans communicate with devices across the internet more easily. As people, we often have trouble remembering complex information like long strings of numbers. That's where DNS becomes useful.

Think of DNS like the internet’s phonebook. Instead of having to remember a computer’s unique number (called an IP address), we can use simple names like google.com.

Every device connected to the internet has its own unique IP address, similar to a home address that tells information where to go. An IP address usually looks like this: 10.0.2.14. It consists of four sets of numbers separated by periods.

Rather than memorizing those numbers, DNS allows us to use easy-to-remember names. It translates those names into IP addresses behind the scenes. It’s like saving someone’s name in your contacts instead of trying to remember their phone number.

Domain Hierarchy

• TLD {Top-Lvl-Domain} = > the last part of a domain name. It's the extension that comes after the final dot. Examples include .com, .org, .net, and more. It is the rightmost part of a domain. For example, in the domain walla.co.il, the .co.il is the TLD. This type of TLD is called a country code TLD and is used for websites based in Israel.

TLDs help classify domains by purpose or region: .com for commercial websites .org for organizations .edu for educational institutions .gov for government sites .co.il for Israeli companies

There are two main types of TLDs: Generic TLDs (gTLDs) such as .com, .net, .org

Country Code TLDs (ccTLDs) such as .uk, .fr, .il

• SLD {Second-Lvl-Domain} = > so if the .co.il is the TLD, then "walla" is the second domain. when registering a domain, the second part ia limited to 63 characters + the TLD can use only a-z 0-9 and hyphens.

• SubDomain = > a part of a larger domain. It comes before the main domain name and is used to organize or separate different sections of a website. For example, in blog.example.com, blog is the subdomain of the main domain example.com. Subdomains can be used for Different services (like shop.example.com, mail.example.com) / ( Development or testing (dev.example.com). They help structure a website without needing a completely new domain.

Record Types

• A record = > records that resolve an IPv4 address, for example 104.26.10.229.
• AAAA Record = > Records that resolve to IPv6 address.
• CNAME Record = > resolve to another domain name. for example 'tet.example.com' return CNAME records 'shops.shopify.com'. another DNS request will be made to work out the IP addrss.

Making A Request

First, the computer checks its local cache to see if the address has already been resolved. If not, a request is sent to the recursive DNS server, typically provided by the ISP. This server also maintains a cache of recently queried domain names. If the record is found, the response is returned immediately. If not, the server initiates a sequence of queries, starting from the internet’s root DNS servers and continuing until the correct answer is found. The root server's job is to redirect our request to the appropriate server. For example, if we request tryhackme.com, the root server identifies the .com top-level domain and refers us to the correct TLD server that handles .com extensions.

The TLD server holds a record indicating where to find the authoritative server responsible for answering the DNS query. It also knows the name server of the domain. For instance, the name server for tryhackme.com is kip.ns.cloudflare.com.
The authoritative DNS server is responsible for storing the DNS records of a specific domain name.