host-based-image-names.md

Host-Based Image Names

This is version 1 of this specification.

The X.509 Public Key Infrastructure provides a well-established mechanism for trusted namespacing of domain names. Protocols interested in leveraging that infrastructure need to be able to extract domain names from image names. This specification provides one approach for that extraction.

This specification defines image names compatible with host names using the following ABNF:

host-based-image-name = host "/" path-rootless [ "#" fragment ]

where:

• host is defined in RFC 3986 section 3.2.2. While IP addresses are valid host names, X.509 certificates usually assert ownership of one or more domain names and do not mention IP addresses. Host-based image names SHOULD use host names that conform RFC 1034's preferred name syntax as modified by RFC 1123 section 2.1.
• path-rootless is defined in RFC 3986 section 3.3.
• fragment is defined in RFC 3986 section 3.5.

Implementations MAY accept other names, for example, by creating a default host for names that match segment-nz (defined in RFC 3986 section 3.3).

Names which are not supported for host-based-image-name will not be able to use protocols that rely on this rule, although they may use other protocols.