Re: Fwd: New Version Notification for draft-jaju-httpbis-zstd-window-size-00.txt

Hi Martin,

Thanks for taking a look and the comments!

I agree that `Content-Encoding: zstd` should mean that encoders use <= 8MB
and decoders support >= 8MB. This is key, and if there's a better way to
word that, I'd love suggestions.

The part that you mentioned about decoders being able to support a
different limit was added as an attempt to explain that deployments of zstd
operating in a private environment that don't care about interoperability
should negotiate it out-of-band. Maybe I could change that text to
something along the lines of:
  "Decoders that wish to support a lower limit and encoders that wish to
emit
  frames requiring a larger window size MUST negotiate the limit
out-of-band."

What do you think? Also, do we need to address this case at all? It
specifically only applies in situations where endpoints aren't trying to
interoperate beyond a short list of peers.

Best,
Nidhi

On Tue, Mar 5, 2024 at 1:12 PM Martin Thomson <mt@lowentropy.net> wrote:

> This seems fine.  And 8M is a fine choice of limit.
>
> However, I don't think that ㄟ( ▔, ▔ )ㄏ is a good interoperability strategy:
>
> > Decoders are free to support higher or lower limits, depending on local
> limitations, if negotiated out-of-band. Many deployments of Zstandard
> operate in controlled, private environments and can directly communicate
> with their encoder and decoder to negotiate a higher or lower limit.
>
> I think that it is obvious that decoders could support more.  But
> supporting less would not be following the standard.  The same goes for an
> encoder that wants a larger window.
>
> We should encourage people to choose a different way of identifying that
> content-coding.  In other words, encoding > 8M or decoding < 8M is not
> Content-Encoding: zstd.
>
> On Tue, Mar 5, 2024, at 14:16, Nidhi Jaju wrote:
> > Hi all,
> >
> > I wrote a draft regarding window sizes in Zstandard Content Encoding
> > that aims to update RFC8878
> > <https://datatracker.ietf.org/doc/html/rfc8878> to require a specific
> > limit for improved interoperability.
> >
> > For context, we recently shipped zstd Content Encoding support in
> > Chrome 123 and came across incompatibilities in the field where
> > developers were confused when their compressed content was not able to
> > be decoded by Chrome, but was correctly decoded by curl and the zstd
> > CLI. Having an explicit agreed-upon limit would help deployers of zstd
> > to align their implementations and cause less user friction.
> >
> > I believe this topic was also previously discussed at
> > https://lists.w3.org/Archives/Public/ietf-http-wg/2021JulSep/0137.html
> > and
> > https://lists.w3.org/Archives/Public/ietf-http-wg/2023JulSep/0178.html.
> > This was also discussed at the W3C WebPerf WG meeting
> > <
> https://docs.google.com/document/d/1ijP7yc6UXZVgzpXDVmBa7h70gxLpFcqdlOZzL3DRT_0/edit#heading=h.xn2d3li0b8op>
>
> > at TPAC 2023.
> >
> > Please let us know what you think.
> >
> > Best regards,
> > Nidhi
> >
> > ---------- Forwarded message ---------
> > From: <internet-drafts@ietf..org <mailto:internet-drafts@ietf.org>>
> > Date: Tue, Mar 5, 2024 at 7:26 AM
> > Subject: New Version Notification for
> draft-jaju-httpbis-zstd-window-size-00.txt
> > To: W. Felix P. Handte <felixh@meta.com>, Nidhi Jaju <
> nidhijaju@google.com>
> >
> >
> > A new version of Internet-Draft
> draft-jaju-httpbis-zstd-window-size-00.txt has
> > been successfully submitted by Nidhi Jaju and posted to the
> > IETF repository.
> >
> > Name:     draft-jaju-httpbis-zstd-window-size
> > Revision: 00
> > Title:    Window Sizing for Zstandard Content Encoding
> > Date:     2024-03-04
> > Group:    Individual Submission
> > Pages:    5
> > URL:
> >
> https://www.ietf.org/archive/id/draft-jaju-httpbis-zstd-window-size-00.txt
> > Status:
> > https://datatracker.ietf.org/doc/draft-jaju-httpbis-zstd-window-size/
> > HTML:
> >
> https://www.ietf.org/archive/id/draft-jaju-httpbis-zstd-window-size-00.html
> > HTMLized:
> >
> https://datatracker.ietf.org/doc/html/draft-jaju-httpbis-zstd-window-size
> >
> >
> > Abstract:
> >
> >    Deployments of Zstandard, or "zstd", can use different window sizes
> >    to limit memory usage during compression and decompression.  Some
> >    browsers and user agents limit window sizes to mitigate memory usage
> >    concerns, causing interoperability issues.  This document updates the
> >    window size limit in RFC8878 from a recommendation to a requirement
> >    in HTTP contexts.
> >
> >
> >
> > The IETF Secretariat