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Re: Question on flow control for a single file transfer

From: Amos Jeffries <squid3@treenet.co.nz>
Date: Tue, 05 Nov 2013 10:02:24 +1300
To: ietf-http-wg@w3.org
Message-ID: <210db200e46446c3602dd1dce5428b6d@treenet.co.nz>
On 2013-11-05 05:05, Peter Lepeska wrote:
> Amos,
> 
> I agree what you said, but again only when there is more than one 
> active
> stream. Again, HTTP 2 flow control is harmless at best when there is 
> only
> one active stream.

Part of my point was that there is absolutely no way to determine that 
one active stream cases existence all the way along the path. Middleware 
exists (whether it is visible to the endpoints or not) and the "single 
stream" may be sharing any HTTP hop with one or more other streams.

"At best" this single stream will be able to avoid contention in the 
more common cases where it ceases being a single end-to-end stream at 
some middel hop. So no I think the best-case is rather better than you 
are saying.


> 
> But you don't have to believe me. Just setup a test a browser that does
> flow control and add a few % loss and 200 ms latency and see whether 
> you
> are able to download large files faster with flow control on or off. 
> The
> flow control off case should never lose, assuming the loss/latency are
> regular and your test is long enough.

At what size data frames? and what relative size of TCP and HTTP layer 
buffer sizes? over how many hops?

In the grand scheme of HTTP, single client going to single server, with 
a single stream and nothing in between is a rather rare occurance. Just 
like it is a rather rare and artificial occurance to see only a single 
isolated TCP connection today.

Amos
Received on Monday, 4 November 2013 21:02:51 UTC

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