Re: Specifying Range in Link preload header for HTTP/2 Push?

Yoav Weiss <yoav@yoav.ws> Wed, 10 July 2019 21:01 UTC

Return-Path: <ietf-http-wg-request+bounce-httpbisa-archive-bis2juki=lists.ie@listhub.w3.org>
X-Original-To: ietfarch-httpbisa-archive-bis2Juki@ietfa.amsl.com
Delivered-To: ietfarch-httpbisa-archive-bis2Juki@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 9D1E012001B for <ietfarch-httpbisa-archive-bis2Juki@ietfa.amsl.com>; Wed, 10 Jul 2019 14:01:17 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2.65
X-Spam-Level:
X-Spam-Status: No, score=-2.65 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, HEADER_FROM_DIFFERENT_DOMAINS=0.249, HTML_MESSAGE=0.001, MAILING_LIST_MULTI=-1, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (2048-bit key) header.d=yoav-ws.20150623.gappssmtp.com
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id B71ScSNciZdA for <ietfarch-httpbisa-archive-bis2Juki@ietfa.amsl.com>; Wed, 10 Jul 2019 14:01:14 -0700 (PDT)
Received: from frink.w3.org (frink.w3.org [IPv6:2603:400a:ffff:804:801e:34:0:38]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 136F1120025 for <httpbisa-archive-bis2Juki@lists.ietf.org>; Wed, 10 Jul 2019 14:01:13 -0700 (PDT)
Received: from lists by frink.w3.org with local (Exim 4.89) (envelope-from <ietf-http-wg-request@listhub.w3.org>) id 1hlJfm-0004EL-II for ietf-http-wg-dist@listhub.w3.org; Wed, 10 Jul 2019 20:58:42 +0000
Resent-Date: Wed, 10 Jul 2019 20:58:42 +0000
Resent-Message-Id: <E1hlJfm-0004EL-II@frink.w3.org>
Received: from mimas.w3.org ([2603:400a:ffff:804:801e:34:0:4f]) by frink.w3.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from <yoav@yoav.ws>) id 1hlJfk-0004DW-PZ for ietf-http-wg@listhub.w3.org; Wed, 10 Jul 2019 20:58:40 +0000
Received: from mail-wr1-x42d.google.com ([2a00:1450:4864:20::42d]) by mimas.w3.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.89) (envelope-from <yoav@yoav.ws>) id 1hlJfi-0008S5-8W for ietf-http-wg@w3.org; Wed, 10 Jul 2019 20:58:40 +0000
Received: by mail-wr1-x42d.google.com with SMTP id g17so3897346wrr.5 for <ietf-http-wg@w3.org>; Wed, 10 Jul 2019 13:58:17 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yoav-ws.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=6m4JcpddKxEIDMhaWcivLHpHbPoOPOwiYVwdSoLisUU=; b=CP8ZM0byi7TqG1FHW6H4EGFcrYayV2OYvjg+GTUpHsbfFHtfopJLeHWkkiHJ+S1wtV 2k4SrlaKjQI9eeUKmCHuGT9wu0T3ImBzM4vuWGecUEKCYap0lbVx2nHLLOe9ZRyxzUmO XuL9W7i0C3bBmmye/jeuJ0suaE2jfunD+4It5+sOVuRMeHGyKR/bSMtuxR46I07dizBz Xptb6PBHAJO3g3UT6QSb48GWLGaWvFFeFz80/dwKiyTOUkWABXEPMjeOG9qhz/ULfd6X 4O7uyAKv/3XDV8Rc77mgZRNVckc5styolvCi/NmavT48JgSWngPtyYQBvQKE6wk/SRWs JyYw==
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=6m4JcpddKxEIDMhaWcivLHpHbPoOPOwiYVwdSoLisUU=; b=KVV0Y/DfQ3QXfwMyiE0A6UEsHXBfB/cYOwBmLahyNFuQj3WRvDCSuz/jcUzXCBxLnr 69PhOiBuTwU4AKgjzxxkvCuXKK4P47qatemPpczk2S81fCnAMVl+F9V8H8X+OhQm+vwB l2wSxxx+NDTWqkh/dqMqTePdvWtJAus3TJA26EJJBsIedWmOcCmUMMUbSxI9hxb6FEj1 qiVfuDE3xZRn/h/Bc7cOW2mb4L25K6jpbar6mfzrT/DAUxtRRoZIGJvR2ZUnPDLqQvyg zbHe0VVZDP1O3Xs9FvyHgqIIUfvRGbTEQL9HLUFYtGDI0Aure9HE6d8CP9nYtyCE2Sx6 DOlA==
X-Gm-Message-State: APjAAAUi1qeO81fLQHBmrWjJixO+BQyRx6XbD6YKD4kYbxOCeveiFvcY yD+Nmw/zOT6b56tYuTTZxd53V1ovC9CDUjLlDcwoBA==
X-Google-Smtp-Source: APXvYqx3lO6KheLzjxCMReC38p0bgpXZBlQRFR9Hv1Yl18pPKkygQy/XZgAt3cKRZr2GE3OqmbmfhHGRR46nSaCdZ4Q=
X-Received: by 2002:a5d:6190:: with SMTP id j16mr33861995wru.49.1562792295570; Wed, 10 Jul 2019 13:58:15 -0700 (PDT)
MIME-Version: 1.0
References: <63CAE7E1-34E9-42DA-A7DD-1E17223032AE@apple.com> <CALGR9oaNnSKp-a8tj+7ojc_g+AhJQ4jF5Z738mjhXhoesfYqLg@mail.gmail.com> <CC99D5CA-1C8B-4200-A6D4-059ABCD6DBA8@apple.com> <D2C627CF-C1D3-459E-8489-CD0530A30A9B@apple.com> <C1CBCD79-7D43-4346-AD79-11658F848126@apple.com> <CACMu3tqTtStsBL1eQ8HPxcyuH7WrTTAKxioob7gN5msZL0HG0A@mail.gmail.com> <732745DA-6CFC-4D02-B052-EDE94C89FC13@apple.com>
In-Reply-To: <732745DA-6CFC-4D02-B052-EDE94C89FC13@apple.com>
From: Yoav Weiss <yoav@yoav.ws>
Date: Wed, 10 Jul 2019 22:57:58 +0200
Message-ID: <CACj=BEiCTVjKKnMmsYhxYXwJT_OoS+zJ5U4q2gCzH_jb+3Wx3g@mail.gmail.com>
To: Roger Pantos <rpantos@apple.com>
Cc: =?UTF-8?Q?Bence_B=C3=A9ky?= <bnc@chromium.org>, HTTP Working Group <ietf-http-wg@w3.org>
Content-Type: multipart/alternative; boundary="000000000000a2b4b1058d59efcc"
Received-SPF: pass client-ip=2a00:1450:4864:20::42d; envelope-from=yoav@yoav.ws; helo=mail-wr1-x42d.google.com
X-W3C-Hub-Spam-Status: No, score=-5.0
X-W3C-Hub-Spam-Report: AWL=3.872, BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, HTML_MESSAGE=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, W3C_AA=-1, W3C_DB=-1, W3C_IRA=-1, W3C_IRR=-3, W3C_WL=-1
X-W3C-Scan-Sig: mimas.w3.org 1hlJfi-0008S5-8W 99af6637c6f73a1eba4bf5dccc23b29d
X-Original-To: ietf-http-wg@w3.org
Subject: Re: Specifying Range in Link preload header for HTTP/2 Push?
Archived-At: <https://www.w3.org/mid/CACj=BEiCTVjKKnMmsYhxYXwJT_OoS+zJ5U4q2gCzH_jb+3Wx3g@mail.gmail.com>
Resent-From: ietf-http-wg@w3.org
X-Mailing-List: <ietf-http-wg@w3.org> archive/latest/36785
X-Loop: ietf-http-wg@w3.org
Resent-Sender: ietf-http-wg-request@w3.org
Precedence: list
List-Id: <ietf-http-wg.w3.org>
List-Help: <https://www.w3.org/Mail/>
List-Post: <mailto:ietf-http-wg@w3.org>
List-Unsubscribe: <mailto:ietf-http-wg-request@w3.org?subject=unsubscribe>

Hey Roger,

If the goal is to extend preload (e.g. with a new attribute), I believe the
best route would be to open an issue on the preload repo
<https://github.com/w3c/preload/issues> with your use-case and we can
discuss it further there. I also believe that such an attribute would be
considered an extension attribute
<https://tools.ietf.org/html/rfc8288#section-3.4.2> from a WebLinking
perspective, but I may be wrong on that front.

Regarding such an attribute, have you considered what would be its impact
on the browser itself? Should the browser use that range for the request as
well? (assuming the header doesn't get stripped off by the server)

Cheers,
Yoav

On Wed, Jul 10, 2019 at 6:34 PM Roger Pantos <rpantos@apple.com> wrote:

>
>
> > On Jul 10, 2019, at 5:10 AM, Bence Béky <bnc@chromium.org> wrote:
> >
> > Hi,
> >
> > FYI I worked on this in Chrome a little more about a year ago, aiming
> > to do something simple, with no particular use case in mind.
>
> > Currently range request pushes are accepted, but matched with requests
> > only if the range matches exactly.  Caching in this case is trivial.
> > I imagine this would be relatively easy to implement in other clients
> > as well.
>
> Hi Bence. Thanks for the additional detail.
>
> >
> > If you could work some client side JS magic to issue requests with the
> > same range that the server has pushed, it would work with Chrome
> > today.
>
> That will be the case in LL-HLS. The primary resource (that triggers the
> push) is actually the active manifest. It contains the URI and byte range
> of the pushed resource. Upon receiving the manifest update the client will
> request that specific range.
>
> > The only caveat is that Chrome only allows one pushed stream
> > with any given URL, so you wouldn't be able to push the second range
> > for the same resource until the first one is matched by a request,
>
> That should be workable.
>
> > which of course the server has no insight into seeing when it happens.
> > I imagine other client might have a similar restriction.  In fact,
> > about 40% of incoming pushes are rejected as duplicate URL, indicating
> > that many servers are pushing the same request repeatedly on a single
> > connection, therefore rejecting such pushes seems like a necessary
> > optimization to avoid wasting downlink.
>
> Agreed, but that shouldn’t happen with LL-HLS. The client affirmatively
> asks for the push at the application layer (via a query parameter on the
> manifest request). It will only ask if it needs the media resource.
>
>
> thanks,
>
> Roger.
>
> >
> > Cheers,
> >
> > Bence
> >
> >
> > On Tue, Jul 9, 2019 at 11:26 PM Roger Pantos <rpantos@apple.com> wrote:
> >>
> >>
> >>
> >> On Jul 9, 2019, at 7:01 PM, Leif Hedstrom <lhedstrom@apple.com> wrote:
> >>
> >>
> >>
> >> On Jul 9, 2019, at 19:05, Roger Pantos <rpantos@apple.com> wrote:
> >>
> >>
> >>
> >> On Jul 9, 2019, at 4:03 PM, Lucas Pardue <lucaspardue.24.7@gmail.com>
> wrote:
> >>
> >> Hi Roger,
> >>
> >> On Tue, 9 Jul 2019, 21:36 Roger Pantos, <rpantos@apple.com> wrote:
> >>>
> >>> Greetings HTTP experts,
> >>>
> >>> I’m interested in employing HTTP/2 Push of Range requests for media
> streaming. It seems like the core h2 protocol handles this well enough; the
> PUSH_PROMISE can contain a Range header, and at the very least if that ends
> up in the client push cache then a request for that exact Range should
> match.
> >>>
> >>> That being said, I’d also like to signal the push request to
> downstream HTTP caches. Push is typically signaled via the Link header with
> rel=preload, but https://www.w3.org/TR/preload/ doesn’t seem to define
> signaling and associated Range.
> >>>
> >>> Has anyone defined a Link extension to signal an associated Range?
> >>
> >>
> >> I've spoken informally to some people on related topics. I presume this
> is related to Apple's LHLS? Or in lay speak, one approach to low-latency
> HTTP-based streaming. It'd be great to have a reference to cite when
> talking around the topic.
> >>
> >>
> >> That’s right. Here’s a link to the current white paper:
> https://developer.apple.com/documentation/http_live_streaming/protocol_extension_for_low-latency_hls_preliminary_specification
> >>
> >>
> >>>
> >>> If not, would anyone object to the following Link extension?
> >>>
> >>> range-link-extension = “range” = ranges-specifier
> >>>
> >>> where ranges-specifier is defined in RFC 2616.
> >>>
> >>> An example would be:
> >>>
> >>> Link: </media.mp4>; rel=preload; as=video; type=video/mp4;
> range=1380-14226
> >>>
> >>>
> >>> thanks,
> >>>
> >>> Roger Pantos
> >>> Apple Inc.
> >>
> >>
> >> The general impression I've observed is that such a range signal in
> Link would be useful to a number of services, and that there would be
> benefit in adopting a common signal.
> >>
> >> Furthermore, while the use of server push might have debatable benefits
> for the web browsing use case. I'm led to believe that it has affirmative
> uses in this streaming model. Again, some evidential data would be really
> interesting.
> >>
> >>
> >> The use of Push in our LL-HLS design eliminates one round trip per
> (partial) media segment downloaded. We’ve got data that shows round trip
> times to media servers can exceed 100 (or even 200) ms, particularly on
> cellular networks, even in the U.S.
> >>
> >> When playing at very low delay-from-live (2s or less), the client can
> only buffer around 1s ahead of the playhead (because that’s all there is).
> New segments must be loaded in a timely fashion to prevent playback from
> stalling. Speeding that up by 10% of the overall budget is a significant
> win.
> >>
> >> In addition, keeping the TCP send pipe full improves lost-packet
> recovery performance of the primary resource that accompanies the push (via
> fast retransmit).
> >>
> >>
> >> Finally, server push and caching is an interesting area that might
> benefit from some more information. Some of the WG might be interested in
> how this gets implemented in your use case.
> >>
> >>
> >> Certainly. I’d be happy to answer as I’m able to.
> >>
> >>
> >> FWIW, server push sort of dictates that you can write the object to
> cache if I recall.
> >>
> >>
> >> Absolutely. That’s what we want.
> >>
> >>
> >> That much said, caching partial objects can be tricky at best. Do you
> treat each range as a unique object ?
> >>
> >>
> >> That’s the simplest approach, and it should work pretty well for
> LL-HLS. From a cache point of view it’s effectively the same as the
> non-byterange case, where each partial segment has its own URL.
> >>
> >> If so, how do you avoid an explosion in various range sizes?
> >>
> >>
> >> There shouldn’t be much of an explosion. The byte ranges pushed are
> determined by the origin, and there won’t be more than about 20 per URL. So
> it hopefully won’t hurt cache search performance too much.
> >>
> >> If you try to combine partial objects into one larger object,  the
> cache code tend to get tricky (we gave up in ATS).
> >>
> >> This is probably something worthwhile discussing to understand the
> implications both on servers and clients. It’s non trivial, but definitely
> interesting!
> >>
> >>
> >> Agreed,
> >>
> >>
> >> Roger.
> >>
> >>
> >> Cheers,
> >>
> >> — Leif
> >>
> >>
> >> If there’s nothing currently defined, what would be the next step? To
> write an Internet-Draft specifying the Link extension?
> >>
> >> (I’m also interested in a way for a server to indicate that pushed
> resources are to be strictly ordered (such as via a dependency tree).
> Today, multiple pushes get multiplexed at the default priority. But that’s
> a different discussion.)
> >>
> >>
> >> Roger.
> >>
> >>
> >> Cheers
> >> Lucas
> >>
> >>
> >
> >
>
>
>