Recorded scope and limits
RFC Editor publication, October 1989. Read section 2.1 for the update to earlier preferred hostname syntax. It is hostname context, not a physical-label format, a complete current DNS implementation guide or a rule for every URL component. Checked October 29, 2026.
Use the task guides below to see how this source informs a labeling decision. Check the publication scope and the edition adopted by your project before applying it. A publisher overview is not the full text of a standard, and software documentation does not prescribe a physical label format.
Read the library’s edition and applicability notes.
What this source establishes
The cited section updates earlier hostname syntax. Validate the actual receiving system; this source does not define physical identifiers.
Review date: 2026-10-29. This note describes the source scope; it is not a project approval.