Which arrangement helps DNS scale by distributing responsibilities among root name servers, TLD name servers, and host name servers?

• A. Division of labor between root name servers, TLD name servers, and host name servers
• B. A single authoritative DNS server for all domains
• C. Only using root servers
• D. Central caching on one machine

Answer: (A)

Dividing DNS duties among the root, TLD, and host name servers creates a scalable, resilient system. The root servers don’t hold the records for every domain; they simply direct queries to the appropriate top-level domain servers. Those TLD servers then point to the authoritative servers for a specific domain, which store the actual DNS records. This delegation distributes workload, so no single server has to handle every lookup. It also enables caching at multiple levels, speeds up repeated queries, and allows independent administration of different zones. If one part of the system faces a problem, the others can continue to function, maintaining overall availability.

Why the other arrangements don’t fit: a single authoritative server for all domains would become a bottleneck and a single point of failure. Relying only on root servers lacks the necessary granularity to locate many domains. Central caching on one machine would not provide proper authority for domains and would still fail under higher load or outages.