Hi Ben,

Thanks for the work on the SVCB draft! It’s in really good shape, in my 
opinion. I’ve commented on these three PRs, but I’ll share my thoughts here as 
well.

> On Feb 18, 2021, at 7:36 AM, Ben Schwartz 
> <[email protected]> wrote:
> 
> The SVCB/HTTPS RR draft is nearing completion, but there are a few remaining 
> topics on which the authors would appreciate feedback from the working group. 
>  Personally, I've written up three proposed changes that would benefit from 
> broader input.  Please share your thoughts.
> 
> 1. Change IANA policy to Specification Required
> (https://github.com/MikeBishop/dns-alt-svc/pull/262/files 
> <https://github.com/MikeBishop/dns-alt-svc/pull/262/files>)
> 
> The current proposed IANA policy for SvcParamKeys has allocatable ranges 
> under three different policies ("Standards Action", "Expert Review", and 
> "First Come First Served").  This is very flexible and enables 
> experimentation, but creates compatibility risk: a FCFS SvcParamKey could be 
> allocated without a clear specification of its zone file syntax, leading to 
> zone file portability issues.
> 
> This proposal would replace all these ranges with a uniform Specification 
> Required policy.  The required documentation is minimal: it is only required 
> to describe the zone file format.

I disagree with the rationale behind this change. I totally agree that we 
should have a clear zone file syntax, but based on RFC 8126 that defines the 
various buckets, FCFS registrations can have requirements for well-formatted 
entries with registry-specific requirements. We can mandate that the 
registration have a clear zone file syntax, without needing to be Specification 
Required. Specification Required requires expert review and is a heavier-weight 
process than what we necessarily need for an experimental range. 

The documentation that’s needed is minimal: the value, the name, and the zone 
file format. These can be entries directly in the registry, and will make the 
registry a more useful resource.

> 
> 2. Skip the default port prefix
> (https://github.com/MikeBishop/dns-alt-svc/pull/230/files 
> <https://github.com/MikeBishop/dns-alt-svc/pull/230/files>)
> 
> Using SVCB with a new protocol requires the initial QNAME to end with 
> _(scheme).$HOSTNAME.  The current text suggests (non-normatively) to add 
> _$PORT for endpoints that are identified by a port number.  This turns out to 
> be inelegant for protocols that almost always use the default port.  For 
> example, in the DNS mapping (draft-schwartz-svcb-dns), this would correspond 
> to names like "_53._dns.resolver.example".
> 
> This proposal would change the guidance to skip the port prefix when starting 
> with the default port (like "_dns.resolver.example").

This is a good change. Ship it!

> 
> 3. Add a SHOULD-level chain length limit for zone owners
> https://github.com/MikeBishop/dns-alt-svc/pull/294/files 
> <https://github.com/MikeBishop/dns-alt-svc/pull/294/files>
> 
> Constructing huge chains of CNAME and AliasMode records is clearly a bad 
> idea, but how huge is too huge?  This change suggests not to use more than 8. 
>  This doesn't change the requirements for resolvers (which are free to impose 
> any limit greater than zero) but it might help us to converge on common 
> behavior.

This seems like a sensible change. I think the recommendation could be less 
that 8, but it shouldn’t be more. Leaving this at 8 seems fine.

Best,
Tommy
> 
> --Ben Schwartz
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