Re: [TLS] draft-ietf-tls-esni feedback

Rob Sayre <sayrer@gmail.com> Wed, 23 October 2019 21:10 UTC

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From: Rob Sayre <sayrer@gmail.com>
Date: Wed, 23 Oct 2019 14:10:23 -0700
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To: Ilari Liusvaara <ilariliusvaara@welho.com>
Cc: Watson Ladd <watsonbladd@gmail.com>, TLS List <tls@ietf.org>
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Subject: Re: [TLS] draft-ietf-tls-esni feedback
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On Wed, Oct 23, 2019 at 8:41 AM Ilari Liusvaara <ilariliusvaara@welho.com>;
wrote:

> On Wed, Oct 23, 2019 at 07:52:33AM -0700, Watson Ladd wrote:
> > On Wed, Oct 23, 2019 at 7:35 AM Bill Frantz <frantz@pwpconsult.com>;
> wrote:
> > >
> > > A perhaps radical suggestion:
> > >
> > > Make the server name field fixed length e.g. 256 bytes. Longer
> > > server names are not supported and clients MUST NOT send them.
> > > (Both client and server can't use them because they won't fit in
> > > the fixed length field.)
> >
> > The limit of server name in DNS is 260 bytes, so that limit already
> > exists. No reason to shorten it elsewhere!
>
> Got a reference for the 260 byte limit?
>


> ...
>
> I can not find any justification for higher limit from any RFC updating
> 1035 or 2181. And I would expect any such limit to have been
> significantly above 253 bytes.
>

I found the rationale here:

https://github.com/tlswg/draft-ietf-tls-esni/pull/54

I think this explanation should be in the draft, too.

thanks,
Rob