| Internet-Draft | DNS Relative Labels | July 2024 |
| van Hartingsveldt | Expires 22 January 2025 | [Page] |
This document defines a new DNS Label Type using the Extension Mechanisms for DNS to indicate when a relative domain name is used.¶
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This document defines a "Relative Label" which may appear within domain names. This new label type enables resource records to be stored with their relative form (e.g. "www" instead of "www.example.com.").¶
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].¶
Relative labels are intended to efficiently solve the problem of using FQDNs when a relative label is wanted. For example, when someone wants to add the MX record "0 mx" instead of "0 mx.example.com." using DNS UPDATE [RFC2136]. It is also useful for DNS providers that store all the records in binary format. Saving data in binary requires less space and the data is already in wire format, but at the moment there is no way to save relative domains.¶
Relative labels can only appear in the end of a relative FQDN, like the zero octet only appears in the end of an absolute FQDN. Message compression is possible when also using the relative label, but because the relative label already gives the possibility to leave out the zone name, message compression will likely have less effect.¶
0 1 2 3 4 5 6 7 +-+-+-+-+-+-+-+-+ |0 1| ELT | +-+-+-+-+-+-+-+-+
As described in [RFC1035], relative domain names are domain names that don't end with a dot.¶
Before records are sorted for DNSSEC [RFC2065] purposes, the resource record MUST be converted to canonical form. This simply happens by replacing the relative label by the whole zone name. Also, the relative label should not appear when doing queries, except for AXFR and IXFR.¶
This document defines one Extended Label Type, termed the Relative Label, and requests registration of the code point 000000 binary in the space defined by [RFC2671].¶
All security considerations which apply to traditional ASCII DNS labels apply equally to binary labels. The canonicalization and sorting rules of section 3.3 allow these to be addressed by DNS Security [RFC2065].¶