# RFC 1123: Host Names and Numbers

> 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.

Canonical page: https://datacenterlabeling.com/references/s80

Original source: [RFC 1123: Host Names and Numbers](https://www.rfc-editor.org/rfc/rfc1123.html)

## Scope of this source

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.

The cited section updates earlier hostname syntax. Validate the actual receiving system; this source does not define physical identifiers.

Source review: 2026-10-29.

Rackstamp provides editorial field guidance. IDs, cases, and worksheet entries are fictional examples unless identified otherwise. Distinguish local conventions from adopted standards. Source notes describe the evidence scope; a linked overview is not the full standard or a project approval.

## Related guidance

- [We do not have a naming convention](https://datacenterlabeling.com/problems/naming-convention)