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

From: Mark Nottingham <mnot@mnot.net>
Date: Fri, 25 Nov 2016 10:35:09 +1100
Cc: Takeshi Yoshino <tyoshino@google.com>, "ietf-http-wg@w3.org Group" <ietf-http-wg@w3.org>, Wenbo Zhu <wenboz@google.com>, Martin Thomson <martin.thomson@gmail.com>
Message-Id: <437A6E14-03A9-42DD-A4B8-921C80EC5729@mnot.net>
To: Van Catha <vans554@gmail.com>
To clarify, we said that the future of WebSockets really isn't in scope for this WG; the proper venue for discussing that is:
  https://www.ietf.org/mailman/listinfo/hybi

What *is* in-scope here is how (if at all) that protocol interacts with HTTP, including HTTP/2; there are several ways you could implement WebSockets over HTTP/2, and a few pitfalls in doing so that the people on this list will be able to give you feedback on.

However, it's hard to do that before there's agreement in the WS community about what the requirements are. Ideally, that community would bring a single proposal that has broad support here for review.

Cheers,


> On 25 Nov. 2016, at 5:39 am, Van Catha <vans554@gmail.com> wrote:
> 
> Thanks for clarification. Unfortunate that so little attention was paid to this.  Looks like some of us will be on HTTP1.1 for a long time.
> 
> On Mon, Nov 21, 2016 at 11:14 PM, Takeshi Yoshino <tyoshino@google.com> wrote:
> 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
> 
> 
> 
> 
> 
> 
> 

--
Mark Nottingham   https://www.mnot.net/
Received on Thursday, 24 November 2016 23:35:42 UTC

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