Read it in context.
P. Mockapetris, ISI, November 1987. Establishes the preferred name syntax for domain labels: letters, digits and hyphen, starting with a letter and ending with a letter or digit, a 63-character label limit, and comparison that ignores case. It constrains an identifier only where one is reused as a host name or DNS label, and says nothing about labeling.
The linked guide explains how this source informs its topic. Check the document’s scope and the edition adopted by your project before applying it. A publisher overview or product guide does not reproduce the full requirements of a standard.
Read the library’s edition and applicability notes.
What this source establishes
Establishes the character set and length limit that apply to a DNS label. It does not establish a labeling requirement.
Review date: 2026-09-16. This note describes the source scope; it is not a project approval.