Re: HTTP/2 flow control <draft-ietf-httpbis-http2-17>

Roland Zink <roland@zinks.de> Fri, 20 March 2015 19:44 UTC

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Date: Fri, 20 Mar 2015 20:38:31 +0100
From: Roland Zink <roland@zinks.de>
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Subject: Re: HTTP/2 flow control <draft-ietf-httpbis-http2-17>
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On 20.03.2015 17:50, Bob Briscoe wrote:
> I believe there is no need for an intermediate node to do flow control 
> for individual streams. It does need to control the whole envelope 
> within which all the streams are flowing through the proxy's app-layer 
> buffer memory (e.g. due to a thick incoming pipe feeding a thin 
> outgoing pipe). The best mechanism for controlling the app-layer 
> buffer consumption of the aggregate connection is for the intermediate 
> node to control the TCP receive window of the incoming stream.
>
I think a HTTP proxy can be much more powerful than just forwarding 
streams from the server. It may return some stream from cache, answer 
some requests directly and forward others, it may even push some 
resources for example from cache. As such I don't see a difference to 
what an HTTP server may want to do.

> That doesn't preclude the intermediate node passing on any per-stream 
> flow control messages emanating from the ultimate receiver so that the 
> ultimate sender controls each stream's rate, which will alter the 
> balance between streams within the overall envelope at the proxy.
>
> Bob

Regards,
Roland