Quiz Entry - updated: 2026.07.14
How is the DNS namespace structured as a hierarchy?
DNS is an inverted tree: an unnamed root at the top, top-level domains like .com and .ch below it, then organizations, then individual hosts — and you read a name right-to-left to walk down it.
The hierarchy is what makes DNS scale: responsibility is delegated level by level, so no one has to know everything.
(Root - has no name)
/ | | \ \
com edu org ch fr <- Top Level Domains (TLD)
| | | |
ibm purdue greenpeace hslu <- Second Level Domains
/ \ |
cs ee www <- Third Level Domains / hosts
| Level | Examples | Administered by |
|---|---|---|
| Root | (nameless) | ICANN |
| TLD | .com, .ch, .org, .edu | a registry (e.g. SWITCH runs .ch) |
| Second level | hslu, google, ibm | the organization / company |
| Third level+ | www, mail, shop | the organization itself |
A Fully Qualified Domain Name (FQDN) like www.hslu.ch is read right to left through the tree: root -> ch -> hslu -> www. So www is just a specific host (a computer) inside the hslu domain, which lives under the ch TLD.
Memory tip: the dots in a domain name are the branch points of the tree, biggest scope on the right.