Hm, well, the analogy I was making is that this is essentially a signal to an application, which happens to be a caching name server. "Other name servers treat them as ordinary names" is not a reason not to list a special-use name in the registry. Ideally we want names like this to have as small an implementation footprint as possible. The reason I am objecting to the idea that this is a special-use name is that it doesn't seem fundamentally different to _tcp, aside from the detail of what software happens to consume it. Special-use names do generally require special treatment by the system, even though we hope that the footprint will be as small as possible. Right now entries in the table are either not global names (which doesn't apply here) or are intended for special purposes (e.g., example.com, invalid), or require a protocol other than DNS to resolve (local, onion).
The case for handling this as a special-use name is that we'd want implementors of naming software to find it in the registry so that they'd know to do it, but I don't think that applies here—the downside to not doing it is that you don't get the new feature, not that something breaks. That's very similar to the downside of not knowing what _tcp means. On Tue, May 15, 2018 at 12:39 PM, Matthew Pounsett <m...@conundrum.com> wrote: > > > On 15 May 2018 at 12:34, Tony Finch <d...@dotat.at> wrote: > >> Ted Lemon <mel...@fugue.com> wrote: >> >> > It might be useful to compare this to labels like _tcp that appear in >> SRV >> > records and elsewhere. >> >> The reason for listing a name in the RCF 6761 registry is because it needs >> special handling of some kind in DNS software. That isn't the case for the >> _underscore names, which (from the DNS point of view) are just ordinary >> domain names that have conventional uses in applications. >> >> I'm going to suggest a modification to your first sentence. The reason > for listing a name int he RFC 6761 registry is because it needs special > handling of some kind in DNS software that would otherwise be unaware of > the special handling required by that name. In this case, the only name > servers that need to handle these names specially are the ones implementing > the technology.. all other name servers treat them as ordinary names. > >
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