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Re: WiSH: A General Purpose Message Framing over Byte-Stream Oriented Wire Protocols (HTTP)

From: Takeshi Yoshino <tyoshino@google.com>
Date: Tue, 22 Nov 2016 13:14:32 +0900
Message-ID: <CAH9hSJbNk83FT0WqB1tHJvEfaU5CMoAaKRdvy8NTb4zgEUdzBw@mail.gmail.com>
To: Van Catha <vans554@gmail.com>
Cc: "ietf-http-wg@w3.org Group" <ietf-http-wg@w3.org>, Wenbo Zhu <wenboz@google.com>, Martin Thomson <martin.thomson@gmail.com>
Ah, no. Martin just warned us that we might face the same issue that SSE
faced.

Mark's suggestion is a separate thing. The co-chairs (Mark and Patrick)
said that this (WiSH) doesn't seems to be a topic that should be discussed
in the HTTP WG given the charter of the WG, I think.

On Sun, Nov 20, 2016 at 12:26 PM, Van Catha <vans554@gmail.com> wrote:

> I do not understand what this means.  Is the suggestion to ignore WiSH for
> now in favor of SSE?
>
> On Fri, Nov 18, 2016 at 1:55 AM, Takeshi Yoshino <tyoshino@google.com>
> wrote:
>
>> I'd like to share the feedback on WiSH from IETF 97.
>>
>> ----
>>
>> Due to limited time, I got just one on-site comment from Martin about
>> comparison with Server-sent event (EventSource).
>>
>> As mentioned in the I-D, yes, this is kinda full-duplex SSE with the WS
>> framing, and it might suffer from unexpected buffering by intermediaries if
>> any as Martin said.
>>
>> WiSH should work well for deployment with TLS only (possibly with some
>> non-TLS part beyond server side front-end but are under control of the
>> service providers). Given the wide trend of encouraging TLS and browser
>> vendors' implementation status of H2, I think we should prioritize layering
>> simplicity than taking care of gain of WiSH/H2/TCP + transparent proxy
>> (with unexpected buffering) case. For H2-less TLS-less environment, we can
>> just use the WebSocket protocol.
>>
>> There can still be some risk of MITM (trusted) proxy and unexpected
>> buffering with AntiVirus/Firewall for deployment with TLS, but other
>> WebSocket/H2 mapping proposals also have issues of possible blocking,
>> buffering, etc. WebSocket/TCP's handshake success rate for non-TLS port 80
>> was also not so good when it started getting deployed, and got improved
>> gradually. I think the problems will get resolved once WiSH is accepted
>> widely, and I believe the total pain and cost would be smaller.
>>
>> ----
>>
>> Mark suggested that we should find some other right place than HTTP WG.
>> I'll discuss this with Mark. Maybe we'll consult the DISPATCH WG.
>>
>> ----
>>
>> Thanks everyone for the feedback.
>>
>> Takeshi
>>
>> On Thu, Nov 3, 2016 at 3:20 AM, Costin Manolache <costin@gmail.com>
>> wrote:
>>
>>> Good timing -  http://httpwg.org/http-extensions/encryption-preview.html is
>>> addressing my concerns for
>>> webpush ( and general 'encrypted content' ), we're still discussing some
>>> details, but for this use
>>> case metadata won't be needed.
>>>
>>> Costin
>>>
>>>
>>> On Tue, Nov 1, 2016 at 10:34 PM Takeshi Yoshino <tyoshino@google.com>
>>> wrote:
>>>
>>>> On Mon, Oct 31, 2016 at 5:57 AM, Wenbo Zhu <wenboz@google.com> wrote:
>>>>
>>>>
>>>>
>>>> On Sun, Oct 30, 2016 at 10:25 AM, Costin Manolache <costin@gmail.com>
>>>> wrote:
>>>>
>>>> Thanks for the answer and pointers. From earlier responses, it seems
>>>> possible to use GET
>>>> or a non-web-stream request to would avoid the extra cost of the
>>>> pre-flight.
>>>>
>>>>
>>>>
>>>> Yeah, at least the Content-Type in the HTTP request gets eliminated.
>>>>
>>>>
>>>> One more question/issue: in some cases it would be good to send some
>>>> metadata (headers) along with binary frames. For example in webpush the
>>>> content is an encrypted
>>>> blob, and needs headers for the key/salt. I would assume a lot of other
>>>> 'binary' messages would
>>>> benefit if simple metadata could be sent along. Would it be possible to
>>>> use one of the reserved
>>>> bits for 'has metadata' and add some encoded headers ? I know in
>>>> websocket they are intended
>>>> for 'extensions', but 'headers' seems a very common use case.
>>>>
>>>> Q about webpush: is the metadata different for each binary message?
>>>>
>>>> We discussed about metadata and how to use one of RSV bits etc. For the
>>>> current version, let's make sure the WS compatibility is fully addressed
>>>> (with minimum wire encoding like WiSH)
>>>>
>>>>
>>>> Agreed. Let's discuss the metadata needs separately. I agree it's
>>>> important.
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> Having the binary frame use some MIME encoding to pass both text
>>>> headers and the binary blob
>>>> is possible - but has complexity and overhead.
>>>>
>>>> OTOH, if the binary blob relies on text headers (metata) to be useful,
>>>> then you probably need define a dedicated MIME encoding.
>>>>
>>>>
>>>>
>>>>
>>>> Costin
>>>>
>>>> On Sun, Oct 30, 2016 at 5:27 AM Takeshi Yoshino <tyoshino@google.com>
>>>> wrote:
>>>>
>>>> Thanks, Van, Costin.
>>>>
>>>> On Sun, Oct 30, 2016 at 2:43 AM, Costin Manolache <costin@gmail.com>
>>>> wrote:
>>>>
>>>> Good point - websocket is widely deployed, including IoT - and the
>>>> header is pretty easy to handle anyways.
>>>> +1.
>>>>
>>>> One question: is this intended to be handled by browsers, and exposed
>>>> using the W3C websocket API ?
>>>> Will a regular app be able to make WiSH requests and parse the stream
>>>> by itself, without browser
>>>> interference ? And if yes, any advice on how it interact with CORS ?
>>>>
>>>>
>>>> The first step would be using Streams based upload/download via the
>>>> Fetch API + protocol processing in JS.
>>>>
>>>> The next step could be either introduction of an optimized native
>>>> implementation of WiSH parser/framer in the form of the TransformStream
>>>> which can be used as follows:
>>>>
>>>> const responsePromise = fetch(url, init);
>>>> responsePromise.then(response => {
>>>>   const wishStream = response.body().pipeThrough(wishTransformStream);
>>>>   function readAndProcessMessage() {
>>>>     const readPromise = wishStream.read();
>>>>     readPromise.then(result => {
>>>>       if (result.done) {
>>>>         // End of stream.
>>>>         return;
>>>>       }
>>>>
>>>>       const message = result.value;
>>>>       // Process the message
>>>>       // E.g. access message.opcode for opcode, message.body for the
>>>> body data
>>>>       readAndProcessMessage();
>>>>     });
>>>>   }
>>>>   readAndProcessMessage();
>>>> });
>>>>
>>>> and provide a polyfill that presents this as the WebSocket API, and (or
>>>> skip the step and) go further i.e. native implementation for everything if
>>>> it turns out optimization is critical.
>>>>
>>>> We need to discuss this also in W3C/WHATWG.
>>>>
>>>> Regarding CORS, if the request includes non CORS-safelisted headers,
>>>> fetch() based JS polyfills will be basically subject to the CORS preflight
>>>> requirement. We could try to exempt some of well defined headers if any for
>>>> CORS like WebSocket handshake's headers and server-sent event's
>>>> Last-Event-Id are exempted. Regarding the proposed subprotocol negotiation
>>>> in the form of combination of the Accept header and the Content-Type
>>>> header, the Accept header is one of the CORS-safelisted headers, so it's
>>>> not a problem. The Content-Type header is considered to be
>>>> non-CORS-safelisted if it's value is none of the CORS-safelisted media
>>>> types. So, WiSH media type would trigger the preflight unless we exclude it.
>>>>
>>>> Origin policy https://wicg.github.io/origin-policy/ might also help.
>>>>
>>>>
>>>>
>>>> Costin
>>>>
>>>> On Fri, Oct 28, 2016 at 12:06 PM Takeshi Yoshino <tyoshino@google.com>
>>>> wrote:
>>>>
>>>> Sorry for being ambivalent.
>>>>
>>>> We can of course revisit each design decision we made for RFC 6455
>>>> framing and search for the optimal again. But as:
>>>> - one of the main philosophies behind WiSH is compatibility with
>>>> WebSocket in terms of both spec and implementation
>>>> - the WebSocket is widely deployed and therefore we have a lot of
>>>> implementations in various languages/platform
>>>> - most browsers already have logic for the framing
>>>> - the framing is not considered to be so big pain
>>>> inheriting the WebSocket framing almost as-is is just good enough.
>>>> Basically, I'm leaning toward this plan.
>>>>
>>>> Takeshi
>>>>
>>>> On Sat, Oct 29, 2016 at 3:12 AM, Takeshi Yoshino <tyoshino@google.com>
>>>> wrote:
>>>>
>>>> On Sat, Oct 29, 2016 at 2:55 AM, Loïc Hoguin <essen@ninenines.eu>
>>>> wrote:
>>>>
>>>> On 10/28/2016 08:41 PM, Costin Manolache wrote:
>>>>
>>>> Current overhead is 2 bytes if frame is up to 125 bytes long - which I
>>>> think it's not very common,
>>>> 4 bytes for up to 64k, and 10 bytes for anything larger.
>>>> IMHO adding one byte - i.e. making it fixed 5-byte, with first as is,
>>>> and next 4 fixed length would
>>>> be easiest to parse.
>>>>
>>>>
>>>> Is making it easy (or easier) to parse even a concern anymore?
>>>>
>>>> Considering the number of agents and servers already supporting
>>>> Websocket, the numerous libraries for nearly all languages and the great
>>>> autobahntestsuite project validating it all, reusing the existing code is a
>>>> very sensible solution.
>>>>
>>>>
>>>> Yeah, I've been having similar feeling regarding cost for
>>>> parser/encoder implementation though I might be biased.
>>>>
>>>>
>>>> There are obviously too many options to encode and each has benefits -
>>>> my only concern was
>>>> that the choice of 1, 2, 8 bytes for length may not match common sizes.
>>>>
>>>> ( in webpush frames will be <4k ).
>>>>
>>>>
>>>> --
>>>> Loïc Hoguin
>>>> https://ninenines.eu
>>>>
>>>>
>>>>
>>>>
>>>>
>>
>
Received on Tuesday, 22 November 2016 04:15:28 UTC

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