DNS Fundamentals — Resolution, Records, and the Hierarchy

Why DNS Is Critical for Telecom

DNS is the phonebook of the internet — it translates human-readable names to IP addresses. But for telecom, DNS does much more. It's the service discovery mechanism for SIP. When a phone needs to find its SIP server, it queries DNS for NAPTR and SRV records that specify not just the IP, but the transport protocol, port, and priority. A DNS failure doesn't just break web browsing — it breaks phone service entirely.

The DNS Hierarchy

DNS is a distributed, hierarchical database:

                    . (root)
                   / | \
               .com .net .io
              /   \
        telnyx.com  google.com
        /    \
    sip.telnyx.com  api.telnyx.com

Root servers (13 logical, hundreds of instances): Know where to find the TLD servers. Operated by organizations worldwide.

TLD servers (.com, .net, .org, .io): Know which authoritative nameservers handle each domain.

Authoritative nameservers: The final answer. Telnyx's nameservers know the IP addresses for sip.telnyx.com, api.telnyx.com, etc.

How DNS Resolution Works

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