1234.nu, something has to turn it into an IP address before a single byte can be sent. That something is DNS — the internet's phone book, spread across millions of servers and stitched together by caching. This is an interactive tour of the lookup walk from the root down, the record types, and how TTLs keep it fast. The demos are illustrative.Step 1 Names are for humans, numbers route packets
Routers move packets using IP addresses, not names. People remember names. DNS bridges the two: it maps a human-friendly domain to the address(es) a machine actually connects to. One name can map to many addresses (for load-balancing and redundancy), and the mapping can change without you ever knowing.
A name resolves to an address
Step 2 The lookup walk, one hop at a time
No single server knows every name. A recursive resolver (usually your ISP's or something like 1.1.1.1) does the legwork: it asks the root servers, which point it at the TLD servers for .nu, which point it at the domain's authoritative servers, which finally give the answer. Step through resolving www.1234.nu:
Step 3 Record types — a name holds more than one answer
A domain's authoritative zone is a set of records, each a type that answers a different question. Click each to see what it is for:
Step 4 Caching & TTL — why the walk happens rarely
If every click did the full root→TLD→authoritative walk, DNS would crawl. So every answer comes with a TTL (time to live): how many seconds a resolver may cache it. While cached, the answer is instant and the upstream servers are never touched. A low TTL means changes propagate fast; a high TTL means less traffic but slower updates.
A cached answer counting down
First lookup is a cache miss (does the walk); repeats within the TTL are instant hits. When the countdown reaches zero the entry expires and the next lookup walks again.
Step 5 Recursive vs authoritative
Two very different jobs share the name "DNS server". A recursive resolver answers "what is the address for X?" by asking around and caching the result — it holds no zone of its own. An authoritative server is the source of truth for specific domains; it answers only for the zones it is configured with, and never asks anyone else.
| Recursive resolver | Authoritative server | |
|---|---|---|
| Question it answers | "Resolve this name for me" | "Here is the record for my zone" |
| Owns the data? | No — caches others' answers | Yes — it is the source of truth |
| Asks others? | Yes — walks root→TLD→auth | No |
| Example | 1.1.1.1, 8.8.8.8, your ISP | The domain's nameservers (NS) |
Step 6 Glossary
| Term | In one sentence |
|---|---|
resolver | The server that does the lookup legwork and caches the result. |
root servers | The top of the tree; they point you at the right TLD servers. |
TLD | Top-level domain (.nu, .com) — its servers know each domain's nameservers. |
authoritative | The server that holds the real records for a domain. |
A / AAAA | Maps a name to an IPv4 / IPv6 address. |
CNAME | An alias: "this name is really that other name". |
TTL | Seconds an answer may be cached before it must be looked up again. |
zone | The set of records an authoritative server is responsible for. |
The whole idea: a resolver walks down a tree of delegations — root → TLD → authoritative — and caches the answer by its TTL. Almost every lookup you make is really just a cache hit; the full walk happens only when the cache is cold or expired.