Which mechanism helps DNS scalability by caching domain ↔ IP mappings on multiple machines?

Which mechanism helps DNS scalability by caching domain ↔ IP mappings on multiple machines?

• A. Using a single global DNS server
• B. Refusing to cache any results
• C. Encrypting DNS queries only
• D. Caching domain ↔ IP mappings on multiple machines

Answer: (A)

Caching domain ↔ IP mappings on multiple machines helps DNS scale because it spreads the lookup work across many servers and closer to users. When a resolver caches a domain’s IP for a period (defined by the DNS record’s TTL), subsequent requests for that domain can be answered from the cache instead of querying authoritative servers every time. This reduces traffic to authoritative servers, lowers response times for users, and provides resilience if some servers are slow or unavailable. The more caches there are across the network, the less any single server has to handle, which is the essence of scalable DNS. In contrast, relying on a single global DNS server would create a bottleneck and a single point of failure. Not caching would keep asking authoritative servers for every lookup, which is slow and unsustainable at large scale. Encrypting DNS queries alone doesn’t address caching or load distribution, and refusing to cache ignores the primary mechanism that makes DNS fast and scalable.

Caching domain ↔ IP mappings on multiple machines helps DNS scale because it spreads the lookup work across many servers and closer to users. When a resolver caches a domain’s IP for a period (defined by the DNS record’s TTL), subsequent requests for that domain can be answered from the cache instead of querying authoritative servers every time. This reduces traffic to authoritative servers, lowers response times for users, and provides resilience if some servers are slow or unavailable. The more caches there are across the network, the less any single server has to handle, which is the essence of scalable DNS.

In contrast, relying on a single global DNS server would create a bottleneck and a single point of failure. Not caching would keep asking authoritative servers for every lookup, which is slow and unsustainable at large scale. Encrypting DNS queries alone doesn’t address caching or load distribution, and refusing to cache ignores the primary mechanism that makes DNS fast and scalable.