òbàdàfídì

October 27, 2025

✓Published

Domain Name System (DNS)

Resource Records

1. Address

This category of records contains the information about the IP address of a domain name. The IP address is used to locate the server that hosts the website or service. It is divide into 2

  1. A (IPv4 Address); this is used to store the IPv4 address of a domain name.
  2. AAAA (IPv6 Address); this is used to store the IPv6 address of a domain name.
bash
dig google.com -t A. # get the ipv4 address of google.com

dig output for google.com A record
bash
dig google.com -t AAAA. # get the ipv6 address of google.com

dig output for google.com AAAA record

2. CNAME (Canonical Name)

This is used create alias for a domain name. For example if you have domain with example.com, and you also have docs.example.com, drive.example.com, these records still point to the same IP Address (example.com) but with different hostnames.

Host Type Value
example.com A 142.234.53.1
docs.example.com CNAME example.com
drive.example.com CNAME example.com
mail.example.com CNAME example.com

3. MX (Mail Exchange)

This record is how servers know which mail server to use for a domain name. It is used to specify the mail server that is responsible for accepting email messages for a domain name. For example I (obadafidi@example.com) sends a mail to my friend (tolulope@yahoo.com) the DNS resolution flow will be like this

  1. The DNS resolver will first look up the MX record for the domain name example.com.
  2. The MX record will specify the mail server that is responsible for accepting email messages for the domain name example.com.
  3. The DNS resolver will then look up the IP address of the mail server using the A record (IPv4)
  4. The mail server will then accept the email message and deliver it to the recipient email server (yahoo.com)
  5. Then the mail server on yahoo.com will authenticate the email message to ensure it is from a trusted source.
  6. The mail server on yahoo.com will then deliver the email message to the recipient's email once verification is complete.
sequenceDiagram participant Obadafidi as Obadafidi@example.com participant GMail as GMail Mail Server participant DNS as DNS Server participant Yahoo as Yahoo Mail Server participant Tolulope as tolulope@yahoo.com Note over Obadafidi,GMail: MX Record Resolution & Mail Delivery Process Obadafidi->>GMail: (1) Sends email to tolulope@yahoo.com GMail->>DNS: (2) Requests MX record for yahoo.com DNS-->>GMail: (3) Returns MX record (Yahoo Mail Server details) GMail->>DNS: (3b) Resolves A record to get IP address of Yahoo Mail Server GMail->>Yahoo: (4) Sends mail data to Yahoo Mail Server Yahoo->>DNS: (5) Verifies that sending mail server (GMail) is authenticated DNS-->>Yahoo: Returns authentication confirmation (SPF/DKIM/DMARC) Yahoo->>Tolulope: (6) Delivers email to tolulope@yahoo.com

Results

1. Lookup real domains

The server responds with the domain name and IP for address for amazon.com


lookup output for amazon.com

Same thing happens for google.com


lookup output for google.com

2. Lookup fake domains


lookup output for invalid domain

Conclusion

DNS resolution is a layered process where record types serve distinct responsibilities, from translating names to IP addresses (A, AAAA) to routing mail (MX) and creating aliases (CNAME). Building this project made those responsibilities concrete and highlighted how small protocol details shape reliability and user experience.

Future Improvements

  1. Write DSN parser
  2. Implement TLS/SSL support
  3. Add support for other DNS record types (TXT, CNAME, etc.)