What is DNS and how do caching, TTL, and forwarders impact name resolution performance?

• A. DNS provides secure channels; caching never expires; forwarders store all results locally.
• B. DNS is only used for email routing; TTL is unrelated; forwarders bypass DNS entirely.
• C. DNS translates hostnames to IPs; caching reduces lookups; TTL controls cache duration; forwarders send queries to upstream servers.
• D. DNS translates IPs to hostnames; TTL controls cache duration; forwarders send queries to upstream servers.

Answer: (C)

DNS translates hostnames to IP addresses, which is what enables devices to reach the correct server on a network. When you resolve a name, the resolver can serve the answer from its cache if the name was looked up recently, so you don’t have to query upstream servers every time. That caching dramatically speeds up repeated lookups and reduces overall network traffic.

TTL, or Time To Live, controls how long a cached answer stays valid. A longer TTL means more subsequent requests are served quickly from the cache, improving performance, but it also means the information might stay stale longer if the underlying data changes. A shorter TTL increases how often the resolver must refresh the data, which can raise lookup latency and traffic but improves freshness.

Forwarders are intermediate DNS servers that take queries and forward them to upstream servers for resolution. Using forwarders can speed things up when they have fast, well-cached responses and a good path to the root/authoritative servers, and they also help centralize DNS management. If forwarders are slow or misconfigured, resolution times can increase.

So this description best captures how DNS works and how caching, TTL, and forwarders influence name resolution performance.