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Re: Submitted new I-D: Cache Digests for HTTP/2

From: Kazuho Oku <kazuhooku@gmail.com>
Date: Wed, 10 Feb 2016 10:50:34 +0900
Message-ID: <CANatvzzUQ+TEFZ5kML+Eagsb_O2pdmWosjMx_xspzrsCTy2hkA@mail.gmail.com>
To: Alcides Viamontes E <alcidesv@zunzun.se>
Cc: Mike Bishop <Michael.Bishop@microsoft.com>, Martin Thomson <martin.thomson@gmail.com>, Amos Jeffries <squid3@treenet.co.nz>, HTTP Working Group <ietf-http-wg@w3.org>
Hi,

2016-02-09 20:46 GMT+09:00 Alcides Viamontes E <alcidesv@zunzun.se>:
>>> Not something that we've implemented yet, but it's a valid scenario.
>
> Pushing 304 works both in Chrome and Firefox:
> https://drive.google.com/open?id=0B2F2m0rSqGCVWFJnTzRWOWFWQmc , we have been
> doing it for some time.

My understanding is that handling of pushed 304 in Chrome and Firefox
is unreliable.

When sending a push, a server cannot be 100% certain if the client has
the resource cached.  In other words, there is always a possibility
that the pushed response will be considered as a response to a
non-conditional HTTP request on the client side.

In other words, browsers that support 304 push should, when matching a
pushed 304 response against a HTTP request, check that the request is
conditional, and use the pushed response only if the request was
conditional (additional checks might be necessary).  Otherwise, the
pushed 304 request must be ignored, and the browser should pull the
unconditional HTTP request.

However, my understanding is that both Chrome (48.0.2564.103) and
Firefox (44.0.1) don't do the check; they consider pushed 304
responses to be a response to a unconditional HTTP request.
Therefore, there is a chance that you would fail to deliver the
correct content if you use 304 push today.

-- 
Kazuho Oku
Received on Wednesday, 10 February 2016 01:51:03 UTC

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