On Tue, Feb 13, 2024 at 9:29 AM Nidhi Jaju <nidhij...@chromium.org> wrote:
> > > On Tue, Feb 13, 2024 at 4:18 PM Yoav Weiss (@Shopify) < > yoavwe...@chromium.org> wrote: > >> Thanks for working on this!! This is extremely exciting! >> >> On Tue, Feb 13, 2024 at 1:11 AM Nidhi Jaju <nidhij...@chromium.org> >> wrote: >> >>> Contact emails >>> >>> nidhij...@chromium.org >>> >>> Explainer >>> >>> >>> https://docs.google.com/document/d/1aDyUw4mAzRdLyZyXpVgWvO-eLpc4ERz7I_7VDIPo9Hc/edit?usp=sharing >>> >>> Specification >>> >>> https://datatracker.ietf.org/doc/html/rfc8878 >>> >>> Design docs >>> >>> >>> https://docs.google.com/document/d/14dbzMpsYPfkefAJos124uPrlkvW7jyPJhzjujSWws2k/edit?usp=sharing >>> >>> Summary >>> >>> Zstandard, or “zstd”, is a data compression mechanism described in >>> RFC8878. It is a fast lossless compression algorithm, targeting real-time >>> compression scenarios at zlib-level and better compression ratios. The >>> "zstd" token was added as an IANA-registered Content-Encoding token as per >>> https://datatracker.ietf.org/doc/html/rfc8878#name-content-encoding. >>> >>> Adding support for "zstd" as a Content-Encoding will help load pages >>> faster and use less bandwidth, and spend less time and CPU/power on >>> compression on our servers, resulting in reduced server costs. >>> >>> Blink component >>> >>> Internals>Network >>> <https://bugs.chromium.org/p/chromium/issues/list?q=component:Internals%3ENetwork> >>> >>> TAG review >>> >>> https://github.com/w3ctag/design-reviews/issues/930 >>> >>> TAG review status >>> >>> Pending >>> >>> Risks >>> Interoperability and Compatibility >>> >>> Servers that have a broken implementation of zstd might exist, but the >>> risk of this is small. Additionally, middleware and middleboxes like virus >>> checkers that intercept HTTPS connections might not support zstd, but might >>> fail to remove it from the Accept-Encoding header in the request. >>> >>> Another known risk is interoperability between clients that support zstd >>> regarding window frame sizes. In Chrome, we limit the window frame size to >>> 8MB to prevent excessive memory usage, but this limit does not exist in >>> curl and when using zstd directly. We have seen very few sites that use a >>> window size larger than 8MB which causes decoding errors, but we have added >>> new net error codes and debugging messages to help them understand what to >>> do in this situation. >>> >> >> I know we discussed >> <https://w3c.github.io/web-performance/meetings/2023/2023-09-TPAC/index.html#h.xn2d3li0b8op> >> this at length at the WebPerfWG. >> Can you summarize developments and/or findings since that discussion on >> that front? >> Should we expect the default output of CLI tools to be compatible with >> what we want to ship here? >> Should we expect interoperability between Chromium and e.g. curl? >> > > We've been discussing it with the zstd team at Meta at > https://github.com/facebook/zstd/issues/2713. The plan is to take it to > the HTTP WG at the IETF and either file an errata or publish a new document > with more strict window size guidelines. The zstd CLI tool currently > supports up to 8MB as a default, so the same limit. The library will use > 128MB by default, however, and Curl currently supports up to 128MB windows. > We expect those defaults to change to match any spec changes. In practice, > we've seen very limited reports of sites running into this limit, and we've > added helpful messages in Chromium to guide anyone who does run into it. > Thanks! Pushing that limit into the standard and having curl (and other tools) follow that makes sense and seems important. Thinking out loud, the main risk here is for folks to be testing their content outside of Chromium (e.g. with curl) and then have that content break in Chromium. At the same time if content is tested in Chromium, it will work in another client that supports larger windows. So the (seemingly small) risk here is one we take on ourselves, rather than risk we externalize on the ecosystem. > >> >> >>> Gecko: Positive ( >>> https://github.com/mozilla/standards-positions/issues/775) >>> >>> WebKit: Positive ( >>> https://github.com/WebKit/standards-positions/issues/168) >>> >>> Web developers: Positive (https://crbug.com/1246971) Meta (Yann and >>> Felix) and Akamai (Nic) are positive about zstd content-encoding on the >>> browser. Meta has collaborated with us to improve the compression ratios >>> for Meta origins during the experiment and is seeing positive user-level >>> results. Alibaba is also supportive of shipping zstd support as they saw >>> massive savings on their origins in terms of server CPU cost. >>> >>> Other signals: >>> >>> Ergonomics >>> >>> While both Zstandard and Brotli are clear wins over gzip >>> content-encoding, which of Zstandard or Brotli to use depends on many >>> factors, and site authors may need to experiment to identify the optimal >>> choice for their content. >>> >>> Zstandard uses more memory for decompression than gzip. However, this is >>> also true for Brotli, and we haven't seen any problems in practice. >>> >>> Activation >>> >>> The "zstd" Content-Encoding is not as widely supported by HTTP servers >>> as gzip. Of the top 5 web servers, Nginx has a third-party module, which >>> should also work for OpenResty (untested). Apache, IIS, and LiteSpeed >>> appear to have no support. Explicit server support is often only necessary >>> for dynamic content. For static (pre-compressed) content, Zstandard can >>> often be supported just by configuration. >>> >>> Only one public CDN is known to be able to compress Zstandard itself, >>> and some CDN's may require custom configuration to pass-through Zstandard >>> correctly. >>> >>> Zstd support is not particularly difficult to implement for a server >>> that already implements multiple content encodings. The C implementation >>> has a straightforward API and there are implementations for many other >>> languages. There is also a lively community of Zstandard enthusiasts which >>> should help accelerate adoption. >>> >>> Security >>> >>> CRIME <https://en.wikipedia.org/wiki/CRIME> and BREACH >>> <https://en.wikipedia.org/wiki/BREACH> mean that the resource being >>> compressed can be considered readable by the document deploying them. That >>> is bad if any of them contains information that the document cannot already >>> obtain by other means. An attacker may provide correctly formed compressed >>> frames with unreasonable memory requirements, and dictionaries may interact >>> unexpectedly with a decoder, leading to possible memory or other >>> resource-exhaustion attacks. It is possible to store arbitrary user >>> metadata in skippable frames, so they can be used as a watermark to track >>> the path of the compressed payload. It is important to note that these >>> concerns apply to all compression formats, not just zstd. >>> >>> To mitigate these risks, similar to Brotli, we'll be advertising support >>> for "zstd" encoding only if transferred data is opaque to proxies, to >>> ensure that resources don't contain private data that the origin cannot >>> read otherwise. >>> >> I'm not sure what that means. Can you elaborate on that? > >>> Adding zstd to third_party/ in Chromium adds a large new code surface >>> that processes untrusted data, which inevitably brings risks of new >>> security holes. However, this is mitigated by the extensive fuzzing and >>> security analysis done on zstd by Google and other community members. >>> >>> Furthermore, zstd is implemented in C, which is not a memory-safe >>> language, and the network service is not yet sandboxed on all platforms. >>> >>> WebView application risks >>> >>> Does this intent deprecate or change behavior of existing APIs, such >>> that it has potentially high risk for Android WebView-based applications? >>> >>> Apps which use a WebView to display content from Meta's servers will >>> suddenly start using Zstandard. Since we've already extensively tested our >>> implementation against Meta's servers in Chrome, no problems are expected. >>> There is a killswitch. No special treatment should be needed. >>> >>> >>> Debuggability >>> >>> No special support needed. >>> >>> Zstd content-encoding support is exposed to the devtools protocol, so >>> developers are able to override it and view the headers from the inspector. >>> >>> A new net error has been added for decoding errors related to window >>> frame size. >>> >>> Will this feature be supported on all six Blink platforms (Windows, Mac, >>> Linux, ChromeOS, Android, and Android WebView)? >>> >>> Yes >>> >>> Is this feature fully tested by web-platform-tests >>> <https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md> >>> ? >>> >>> Yes (https://wpt.fyi/results/fetch/content-encoding/zstd >>> <https://wpt.fyi/results/fetch/content-encoding/zstd?label=experimental&label=master&aligned> >>> ) >>> >>> Flag name on chrome://flags >>> >>> enable-zstd-content-encoding >>> >>> Finch feature name >>> >>> ZstdContentEncoding >>> >>> Requires code in //chrome? >>> >>> False >>> >>> Tracking bug >>> >>> https://bugs.chromium.org/p/chromium/issues/detail?id=1246971 >>> >>> Launch bug >>> >>> https://launch.corp.google.com/launch/4266275 >>> >>> Measurement >>> >>> https://chromestatus.com/metrics/feature/timeline/popularity/4629 >>> >>> Adoption plan >>> >>> In our experimental group, around 1% of responses use "zstd" >>> content-encoding. Given the significant benefits of zstandard over gzip, >>> we'd like to see it increase to 10% within 2 years. >>> >>> Estimated milestones >>> >>> Shipping on desktop >>> >>> 123 >>> >>> DevTrial on desktop >>> >>> 117 >>> >>> Shipping on Android >>> >>> 123 >>> >>> DevTrial on Android >>> >>> 117 >>> >>> Shipping on WebView >>> >>> 123 >>> >>> >>> Anticipated spec changes >>> >>> Open questions about a feature may be a source of future web compat or >>> interop issues. Please list open issues (e.g. links to known github issues >>> in the project for the feature specification) whose resolution may >>> introduce web compat/interop risk (e.g., changing to naming or structure of >>> the API in a non-backward-compatible way). >>> >>> The current standard, RFC8878, doesn't require a limit on the window >>> size used by HTTP servers when compressing Zstandard. An update of some >>> form will be needed to ensure interoperability. >>> >>> Link to entry on the Chrome Platform Status >>> >>> https://chromestatus.com/feature/6186023867908096 >>> >>> Links to previous Intent discussions >>> >>> Intent to Prototype: >>> https://groups.google.com/a/chromium.org/g/blink-dev/c/GDsI0Hw-jYk/m/Yc5QZWD-AwAJ >>> >>> Intent to Experiment: >>> https://groups.google.com/a/chromium.org/g/blink-dev/c/I6IWfl95gRU >>> >>> >>> This intent message was generated by Chrome Platform Status >>> <https://chromestatus.com/>. >>> >>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "blink-dev" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to blink-dev+unsubscr...@chromium.org. >>> To view this discussion on the web visit >>> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAMZNYAN7VRca4VfRqP7pi%2BnqwDuor4ZVjF9yDNH1mZcXteQURw%40mail.gmail.com >>> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAMZNYAN7VRca4VfRqP7pi%2BnqwDuor4ZVjF9yDNH1mZcXteQURw%40mail.gmail.com?utm_medium=email&utm_source=footer> >>> . >> >> -- You received this message because you are subscribed to the Google Groups "blink-dev" group. 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