Re: #645: Privacy impact of connection coalescing

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On 22/11/2014 4:20 a.m., Patrick McManus wrote:
> On Fri, Nov 21, 2014 at 2:19 AM, Martin Thomson wrote:
> 
>> On 20 November 2014 17:28, Mark Nottingham wrote:
>>> <https://github.com/http2/http2-spec/pull/647>
>>> 
>>> Any thoughts?
>> 
>> I like the correlation text, that's a real issue.
> 
> 
> agreed - the term origin might be stronger than 'site' as currently
> used.
> 
> 
>> I'm lukewarm on the value of the SETTINGS/PING thing.  TCP
>> window scaling relies on knowing RTT, so another way of measuring
>> it in a
>> 
> 
> h2 bits are e2e

That is wrong. Any h2 intermediaries will likely be varying the RTT
based on work being done for unrelated clients traffic. Stream windows
may also be scaled down/up at each hop depending on the various hops
capabilities. The way the h2 spec is written intermediaries have to do
a *lot* of transcoding work to pass traffic around.
 Clients workloads will impact on each others behaviour in randomly
varied amounts as things scale.
 The only thing e2e about the h2 transfer is per-stream window size.
And all that tells is how many bytes the network can afford to buffer
along the way.

In reality *HTTPS* (HTTP over TLS) is where the e2e predictability
problems start to occur in measurable amounts. Since clients traffic
is distinctly segregated from each other and A-to-B encryption
enforces large sections of the network to become measurable single-hops.

Amos

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Received on Friday, 21 November 2014 16:21:27 UTC