Re: negotiated protocol in Navigation and Resource Timing

On Thu, Oct 16, 2014 at 3:36 PM, William Chan (陈智昌) <willchan@chromium.org>
wrote:
>
> > On Oct 16, 2014, at 3:13 PM, Ilya Grigorik <igrigorik@google.com> wrote:
> > On Thu, Oct 16, 2014 at 10:05 AM, William Chan (陈智昌) <
> willchan@chromium.org>
> > It may make sense to provide protocol info on the Response object, but I
> > don't think that's a strong argument against exposing the protocol in
> RT/NT.
> > There are some rough plans to allow retrieving Response object from an
> > element (e.g. <img>), but that's an involved affair that requires
> iterating
> > over the DOM, and it still doesn't cover the case of the parent page
> > (covered by NT) -- i.e. I can't get the Response object for the
> navigation.
>
> Mostly I'd prefer not to duplicate data in multiple places.
>

We need protocol info in Navigation Timing because there is no way to get
the Response object for the navigation. That said, I would also like to see
it on Resource Timing: developer convenience, consistent API interface.

Also, right now we're working on the assumption that Fetch's Response
object could/should expose the protocol.

*Anne: *any thoughts on the latter?


> >> * How is this property populated when serving from cache?
> > Hmm, good question. Empty value?
>
> Btw, we already leak whether or not a response was cached in other
> ways, right? This should be mentioned in the privacy considerations.
>

Not sure "leak" is the right word. It has always been possible to test for
this: time the request, modify the URL to cache-bust and time that, compare
the two and voila.. a pretty solid way to answer the "in cache" question.
That said, yes, an empty protocol value for a cache fetch makes this
explicit - something we should document in privacy+security sections.


> >> * Are we restricted to ALPN Protocol IDs? What about experimental
> >> protocols like QUIC?
> >
> > I'll defer to Mark on this one :)
>
> Well, I'm going to insist on being able to experiment. And ALPN is an
> interesting choice since QUIC obviously doesn't get deployed using
> ALPN :P
>

https://github.com/w3c/navigation-timing/issues/2#issuecomment-59127537

ALPN ID is simply the namespace / shared registry of names, and QUIC can
register own values as it revs each version. There is no requirement that
you actually use ALPN.


> > I think this falls into same bucket as cached response. Empty value?
>
> I forget how SW interacts with NT/RT, but I sorta view this as a
> reason to tag the protocol in the Response object. The SW may be
> initiating fetches from the worker context rather than a document
> context, so there's no document RT/NT to report the resource fetch.
>

I don't think it's "forget"... it's undefined, and something we should
discuss in a separate thread.

ig