DNSlevel

DNSlevel is a term used in the Domain Name System (DNS) to describe the depth of a domain name within the DNS namespace. It is typically defined as the number of labels in a domain's fully qualified domain name (FQDN), measured from the DNS root as level 0. In this scheme, the top-level domain (such as com or org) has level 1, a second-level domain like example.com has level 2, and a subdomain such as www.example.com has level 3. The root itself is not visible in regular FQDN notation but is considered level 0 in many explanations of hierarchy.

DNSlevel is used in diagnostic and monitoring contexts to quantify how far a query must traverse the DNS hierarchy, which can correlate with latency, cache behavior, and policy application. It can be helpful in debugging delegation failures, routing optimizations, or safety policies that apply at certain depths (for example, restrictions on subdomains).

In practice, DNSlevel is an informal concept and not a formal measurement defined by core DNS standards. Implementations and tools may expose the depth as needed for human operators, often using the count of labels in an FQDN. Edge cases include internationalized domain names (IDNs), which may be represented in punycode, and empty or apex labels in DNSSEC contexts.

See also: DNS, FQDN, DNS hierarchy, DNSSEC, RFC 1034, RFC 1035.