How does DNS resolve a domain name to an IP address, including caching and recursion?

How does DNS resolve a domain name to an IP address, including caching and recursion?

• A. The resolver queries root servers, then TLD servers, then authoritative servers; caching and TTL reduce subsequent queries; recursion is performed by the resolver until an IP is returned or failure.
• B. The resolver queries authoritative servers directly, bypassing root and TLD.
• C. DNS queries are always handled entirely by the client browser with no server involvement.
• D. Root servers store every domain's IP address directly.

Answer: (C)

DNS resolution relies on a hierarchical process where a recursive resolver handles the query on behalf of the client, using a sequence of referrals and caching to translate a domain name into an IP address. When a client asks to resolve a name, the resolver first contacts a root name server. The root doesn’t know the address of every domain; instead, it directs the resolver to the appropriate top-level domain server for the domain’s suffix (like .com, .org, or a country code). The TLD server then points the resolver to the authoritative server that actually holds the mapping for the specific domain. The resolver queries that authoritative server, which returns the final IP address. That result is passed back to the client, and the resolver caches it for future requests according to the time-to-live value. If another request comes in for the same name while the cache entry is valid, the resolver can answer from cache without repeating the full chain. This caching reduces load and speeds lookups, while TTLs ensure that outdated information eventually expires. It’s not the client browser alone doing all the work; a DNS resolver—often part of the OS, a router, or an ISP—performs the recursive lookups and manages caching. The root servers don’t store every domain’s IP; they simply direct queries to the next step, and the real domain mappings live on the authoritative servers.

DNS resolution relies on a hierarchical process where a recursive resolver handles the query on behalf of the client, using a sequence of referrals and caching to translate a domain name into an IP address. When a client asks to resolve a name, the resolver first contacts a root name server. The root doesn’t know the address of every domain; instead, it directs the resolver to the appropriate top-level domain server for the domain’s suffix (like .com, .org, or a country code). The TLD server then points the resolver to the authoritative server that actually holds the mapping for the specific domain. The resolver queries that authoritative server, which returns the final IP address. That result is passed back to the client, and the resolver caches it for future requests according to the time-to-live value. If another request comes in for the same name while the cache entry is valid, the resolver can answer from cache without repeating the full chain. This caching reduces load and speeds lookups, while TTLs ensure that outdated information eventually expires. It’s not the client browser alone doing all the work; a DNS resolver—often part of the OS, a router, or an ISP—performs the recursive lookups and manages caching. The root servers don’t store every domain’s IP; they simply direct queries to the next step, and the real domain mappings live on the authoritative servers.