Re: [Add] questions about the Examples section of svcb-dns-02

[Peter van Dijk <[e-mail]>]

Hi Ben,

thank you for adding all those examples, this should unconfuse many
readers.

(I picked this email to reply to, instead of end of thread, because I'm
typing something more inline below).

On Thu, 2021-04-08 at 11:05 -0400, Ben Schwartz wrote:
> OK, I've clarified (and corrected, oops) the explanation of the examples, and added another one to highlight the default-DoT behavior: https://github.com/bemasc/svcb-dns/commit/e59c995fa976a19b5baf1770afb231d3dcb729e1
> 
> We can certainly remove the default ALPN, but personally I like having empty SvcParams correspond to a common default.  The size savings (~8 bytes) are probably not important, although MTU could become relevant in the context of SVCB delegation responses as envisioned by draft-rescorla-dprive-adox.

I think this one hits the core of the problem for me. I'm not confused
about what -empty- SvcParams mean. I am (well, I was) confused by
alpn=h2,h3 meaning alpn=dot,h2,h3.

So I wonder if having a default, but alpn= always *replacing* that
default instead of appending to it, might make more sense. It certainly
feels clearer to me.

In terms of packet size, some records may spend four more bytes on
'dot,' because they do combine it with DoH in one SVCB record. Other
records will spend a few bytes less on not needing no-default-alpn. I
don't know how this balances out in the end.

Kind regards,
-- 
Peter van Dijk
PowerDNS.COM BV - https://www.powerdns.com/