Re: Broader discussion - limit dictionary encoding to one compression algorithm?

On Tue, May 21, 2024 at 12:41 PM Poul-Henning Kamp <phk@phk.freebsd.dk>
wrote:

> Patrick Meenan writes:
>
> > ** The case for a single content-encoding:
> > […]
> > ** The case for both Brotli and Zstandard:
>
> First, those are not really the two choices before us.
>
> Option one is:  Pick one single algorithm
>
> Option two is:  Add a negotiation mechanism and seed a new IANA registry
> with those two algorithms
>
> As far as I can tell, there are no credible data which shows any
> performance difference between the two, and no of reason to think that any
> future compression algorithm will do significantly better.
>

We already have a negotiation mechanism.  It uses "Accept-Encoding" and
"Content-Encoding" and the existing registry. Nothing about the negotiation
changes if we use one, two or more. The question is if we specify and
register the "dcb" content-encoding as well as the "dcz" content encoding
as part of this draft or if we only register one (or if we also add a
restriction that no other content encodings can use the dictionary
negotiation).

As far as future encodings, we don't know if any algorithms will do better
but there is the potential for content-aware delta encodings to do better
(with things like reallocated addresses in WASM, etc). More likely, there
will probably come a time where someone wants to delta-encode
multi-gigabyte resources where the 50/128MB limitations laid out for "dcb"
and "dcz" won't work and a "large window" variant may need to be specified
(as a new content encoding).