Networking
DNS (Domain Name System)
The internet's phone book that translates human-readable domain names into IP addresses that computers use.
The Domain Name System (DNS) is a hierarchical and distributed naming system that translates human-friendly domain names (like clarkes.team) into IP addresses (like 192.168.1.1) that computers use to identify each other.
How DNS Works
When you type a URL in your browser:
- Browser cache check: Has this been looked up recently?
- OS cache check: Did your computer save it?
- Resolver query: Your ISP’s DNS resolver is asked
- Root server: Points to the TLD (.com, .team) server
- TLD server: Points to the domain’s nameservers
- Authoritative nameserver: Returns the actual IP address
- Response cached: Saved for future requests
This all happens in milliseconds.
Common DNS Record Types
| Record | Purpose |
|---|---|
| A | Maps domain to IPv4 address |
| AAAA | Maps domain to IPv6 address |
| CNAME | Creates an alias to another domain |
| MX | Specifies mail servers |
| TXT | Text records (often for verification) |
| NS | Specifies authoritative nameservers |
DNS Best Practices
- Use a reliable DNS provider: Cloudflare, Route53, Google DNS
- Set appropriate TTLs: Balance caching vs. flexibility
- Configure SPF, DKIM, DMARC: Protect email from spoofing
- Have backup nameservers: Redundancy is essential
- Monitor DNS propagation: Changes can take 24-48 hours
DNS Security
- DNSSEC: Authenticates DNS responses
- DNS over HTTPS (DoH): Encrypts DNS queries
- DNS over TLS (DoT): Alternative encryption method
Improperly configured DNS is a common source of website outages and email delivery issues.
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