See when a resolver needs the DNS hierarchy
Compare three cache states for the fixed query www.example.com. A. Step through the roles without sending a domain or making a DNS query.
Fixed synthetic query
Cold cache
www.example.com. A
With no usable cached answer or delegation, the resolver follows referrals from the root toward the authoritative service.
- Learning steps
- 7
- Upstream DNS queries
- 3
- Services skipped
- 0
Query count is for this simplified learning path, not a packet-count promise.
Client asks its recursive resolver
The client-side stub sends one recursive query for www.example.com. type A to its configured resolver.
What this establishes: The stub asks for recursive service; it does not walk the DNS hierarchy itself.
Complete text path
Client asks its recursive resolver
Stub resolver: The client-side stub sends one recursive query for www.example.com. type A to its configured resolver.
What this establishes: The stub asks for recursive service; it does not walk the DNS hierarchy itself.
Resolver finds no usable cache entry
Recursive resolver: The resolver checks its cache and finds neither a final answer nor a usable cached delegation for this simplified path.
What this establishes: A cache miss explains why upstream resolution starts; it does not identify a DNS failure.
Root refers the resolver to com
Root service: The resolver asks a root server and receives a referral toward authoritative servers for the com zone.
What this establishes: The root response is a direction to the next zone, not the final website address.
com refers the resolver to example.com
com authoritative service: The resolver follows the referral and asks a com server, which returns the example.com delegation.
What this establishes: The parent zone publishes the child nameserver delegation and may include eligible glue.
Authoritative service returns the answer
example.com authoritative service: The resolver asks the service authoritative for example.com and receives the synthetic A answer for www.example.com.
What this establishes: This server answers from zone authority; it does not perform recursive resolution for the client.
Resolver processes and caches the result
Recursive resolver: The resolver applies policy, performs DNSSEC validation where applicable, and caches eligible data using its TTL.
What this establishes: Retries, aliases, validation records, and transport fallback can add work outside this simplified path.
Resolver replies to the client
Recursive resolver: The recursive resolver returns its result to the stub after using cached data or completing the required upstream work.
What this establishes: The response is evidence from this resolver at this time, not a universal Internet state.
What this path skips
Nothing. The cold-cache model visits root, com, and example.com authoritative services.
Model boundaries
- The fixed query is an example-only scenario; its answer and exchanges are synthetic. The page never asks the DNS.
- Upstream retries, multiple server addresses, aliases, qname minimisation, DNSSEC records, transport fallback, and local policy can add or change exchanges.
- A root or parent response is normally a referral, not the final website address.
- Cached state belongs to one resolver. It does not describe every resolver or a global propagation percentage.
Read the sourced explanation in How a DNS lookup travels from root to answer.