> On Nov 14, 2019, at 10:18 AM, Mirja Kuehlewind <[email protected]> wrote:
> 
> Hi taps folks (also cc’ing the WebTransport list),
> 
> I assume that people on the taps list are aware of the WebTransport effort 
> that will have a BoF meeting on 13:30-15:00 Wednesday. I had another look at 
> the WebTransport documents today in order to better understand the scope of 
> WebTransport compared to taps. 
> 
> Looking at https://tools.ietf.org/html/draft-vvv-webtransport-overview-00 I 
> believe that this should be covered by pooled connections in taps + use of 
> partial messages. WebTransport proposes to use streams as the base concept 
> while we in taps explicitly decided against this but to use messages instead 
> which also aligns with other protocols that are discussed in WebTransports 
> like Websockets and WebRTC data channels. Unfortunately the draft doesn’t 
> give any reasoning for that choice but I would still think that use of 
> particle messages in taps should be equivalent at it is explicitly designed 
> to address applications that actually need streaming. What do people think?

I think the notion of stream here is just a multiplexing concept; the 
terminology doesn't follow the terminology in TAPS, but it's not at odds. It's 
just a different phrasing.

> 
> Further looking at https://tools.ietf.org/html/draft-vvv-webtransport-quic-00 
> this draft defines a new ALPN value and a QUIC extension. I guess in taps we 
> have not explicitly considered ALPN so far but we really would need to do 
> that in any case! I guess one could see this as a protocol specific property 
> but maybe it’s even worth to be more explicit here. Did anybody consider ALPN 
> already?

ALPN is a TLS option, so it fits into the protocol-specific options. We 
certainly have support for that in our implementation! 
(https://developer.apple.com/documentation/security/2976269-sec_protocol_options_add_tls_app?language=objc)

> 
> Regarding the new QUIC transport parameter I have to say that the purpose it 
> not fully clear to me from the draft. However it seems that this is supposed 
> to support some kind of access control that is performed on the application 
> layer but by a more trusted entity than the client application itself. It is 
> not fully clear to me what the trust assumptions are, however it does seems 
> that is should not be a transport parameter that is protocol specific but 
> rather some function on the higher layer. However, to be able to make a 
> proposal here, I would probably need to understand the purpose better. Do 
> people have any insights?

From the TAPS side, transport parameters in QUIC do need to be able to be 
configured by the app or set as a default for a given use case, so that 
shouldn't be an issue.

> 
> Do people have thoughts? What is missing in taps to also cover the full web 
> use case? Is that something we want to account for in taps? Or what is the 
> difference that would not fit with the taps approach? What am I missing?

Fundamentally, TAPS is about API shape and approach. It alone doesn't define 
any new protocol knobs. If WebTransport needs new on-the-wire protocol changes, 
those need to be independent. However, the shape of creating connections, and 
sending and receiving messages, is something that can certainly conform to a 
TAPS-compliant interface.

If you read through draft-vvv-webtransport-overview, it largely outlines 
something that is a TAPS interface, just without referencing TAPS or calling 
that out.

So, one way to view the relationship is that WebTransport as described is a 
specific set of protocol features that a web-focused implementation of a TAPS 
system ought to build, plus a few protocol tweaks below.

Thanks,
Tommy

> 
> Mirja
> 
> 
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