Which statement correctly describes the function of TTL in DNS caching?

• A. TTL determines the number of DNS servers queried for a domain.
• B. TTL controls how long a DNS record is cached by resolvers.
• C. TTL sets the encryption strength for DNS queries.
• D. TTL fixes the DNS zone's expiration date.

Answer: (B)

TTL in DNS caching controls how long a DNS record is cached by resolvers. The TTL value, set on the record by the zone administrator, tells caches how long they can keep the answer before asking for a fresh lookup. This helps manage load on authoritative servers while balancing how current the data is. While a record is cached, resolvers will respond with the stored information even if the authoritative source changes, until the TTL expires. After expiration, the next query prompts a new lookup to update the cached data. A long TTL reduces query traffic but slows propagation of changes; a short TTL allows quicker updates but increases the number of queries. The other statements don’t fit because TTL isn’t about how many DNS servers are queried, nor about encryption strength, and TTL isn’t the mechanism that fixes a zone’s expiration date—that’s managed by the zone’s SOA expire setting, not the TTL on individual records.