DNS Explained

The Domain Name System (DNS) is often described as the “phonebook of the Internet.” It translates human-readable domain names (such as `example.com`) into IP addresses (such as `93.184.216.34`) that computers use to communicate.

Without DNS, users would have to remember the IP address of every website they visit.

When you enter a domain name into your browser, the following steps occur:

1. Resolver (usually your ISP's DNS server or a public resolver such as Google DNS `8.8.8.8` or Cloudflare DNS `1.1.1.1`) receives the query.
2. The resolver checks whether it already has the answer cached.
3. If not cached, the resolver queries a Root DNS Server.
4. The root server directs the resolver to the appropriate Top-Level Domain (TLD) Server (such as `.com`, `.org`, or `.ir`).
5. The TLD server tells the resolver which Authoritative DNS Server is responsible for the domain.
6. The authoritative server returns the requested DNS record (A, AAAA, MX, TXT, etc.).
7. The resolver caches the answer according to its TTL (Time To Live) and returns it to your browser.

Browser
   │
   ▼
Recursive Resolver
   │
   ▼
Root Server
   │
   ▼
TLD Server
   │
   ▼
Authoritative DNS Server
   │
   ▼
DNS Record

It is important to distinguish between these two server types.

An authoritative DNS server stores the official DNS records for a domain.

Example:

example.com
    │
    └── ns1.example.com
            ├── A      → 93.184.216.34
            ├── AAAA   → 2606:...
            ├── MX     → mail.example.com
            ├── TXT    → v=spf1 include:_spf.example.com ~all
            └── CAA    → letsencrypt.org

Whenever DNS information changes, these servers are the source of truth.

TTL (Time To Live) specifies how long a DNS record may be cached before it must be queried again.

Example:

Short TTL values allow DNS changes to propagate more quickly but increase the number of DNS queries.

DNS responses may vary because:

• Different resolvers may still have cached records.
• CDN providers return different IP addresses based on the user's geographic location.
• DNS propagation may still be in progress after a recent change.
• Some providers implement GeoDNS or Anycast routing.

This is why querying multiple DNS servers is useful when troubleshooting DNS issues.

After changing a DNS record, not all users will see the change immediately.

Propagation time depends on:

• The TTL of the previous record.
• Resolver cache expiration.
• ISP caching policies.

Although changes are published immediately on the authoritative server, recursive resolvers around the world may continue serving cached data until the TTL expires.

Telenegar DNS Check queries DNS records from multiple DNS providers and geographic locations, allowing you to:

• Compare responses from different DNS servers.
• Detect DNS propagation issues.
• Verify GeoDNS and CDN behavior.
• Query A, AAAA, MX, TXT, NS, SOA, PTR, CNAME, and other DNS record types.

Use our DNS Check tool to investigate DNS resolution from multiple locations.

dns networking dnssec authoritative resolver propagation ttl