On Mar 14, 2020, at 4:00 AM, Mark Delany <[email protected]> wrote:
> Methinks the safest outcome is that TXT substrings should be treated > as an artifact of the limitations of TXT RRs or a side-effect of > serialization and should have no semantic value whatsoever. I largely share the sentiment. At this point it looks like the above interpretation would most closely conform to existing practice. I know of no specifications that concatenate TXT RR strings with spaces. This makes sense given that TXT RRs are not ASCII natural language prose, but are rather what we generally call "octet-strings". There is however at least one counter-example to declaring that TXT carries just a single concatenated (with an empty joiner) logical string. For example, in DNS-SD https://tools.ietf.org/html/rfc6763, each substring in a TXT RR is a separate "key=value" pair. The DNS-SD TXT RRs are distinguished from unrelated TXT RRs by sharing the "_service._protocol" prefixes of the corresponding SRV RRs, so would not in practice be confused with e.g. SPF or DKIM where the rules are as proposed by Mark. So while I've found no existing practice of joining with spaces, there is it seems an expectation that the component substrings can be separately meaningful in some applications. So my take is that applications that expect a single string per TXT record should just join without inserting spaces, while applications that expect multiple values can use the verbatim substrings without concatenation. -- Viktor. _______________________________________________ dns-operations mailing list [email protected] https://lists.dns-oarc.net/mailman/listinfo/dns-operations
