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Re: #541: CONTINUATION - option #4

From: Willy Tarreau <w@1wt.eu>
Date: Mon, 7 Jul 2014 10:54:09 +0200
To: Mark Nottingham <mnot@mnot.net>
Cc: Jason Greene <jason.greene@redhat.com>, K.Morgan@iaea.org, Martin Thomson <martin.thomson@gmail.com>, adrian.f.cole@gmail.com, tatsuhiro.t@gmail.com, ietf-http-wg@w3.org
Message-ID: <20140707085409.GA32346@1wt.eu>
Hi Mark,

making a quick comment about this below :

On Mon, Jul 07, 2014 at 06:10:25PM +1000, Mark Nottingham wrote:
> Thinking through deployment scenarios --
> 
> a) Imagine a forward proxy that has a single connection to the user agent.
> Each time the UA requested an origin that necessitated a new connection, the
> proxy would have to advertise a new, lower request MHS if the origin
> advertises one less than the current client connection's. It could only raise
> the UA->proxy request MHS again when that connection is no longer in use by
> the client (and it'd likely need to use some heuristic to figure this out).
> This isn't great, because you're effectively getting the smallest MHS you're
> currently connected to (for some value of "currently"), and it's dynamic.

I think you're mixing two sides. Here the proxy does not have to impact one
client's MHS depending on the other ones. At best it would impact the MHS on
the connections to the origin server. The MHS is a property of the connection
and does not have to be transferred between the two sides (better, must not).

>From this point on, the proxy can decide whether or not some client connections
may be coalesced to the origin server. If one is watching a video while another
one is loading some CSS, it's likely that we'll make better use of at least two
connections. Just like we'd prefer to have two if one is watching a video at
16kB data frames while someone else is doing some very interactive stuff like
using a WYSIWYG editor or simply benefiting from auto-completion on a search
engine.

Thus I'm pretty sure that forward proxies (and probably reverse proxies as
well) will try to assign streams to connections based on some form of QoS.
If it has to be done for data, for sure it will be needed on headers. Imagine
the large number of small companies still running on ADSL with 4M/1M or so,
you definitely don't want there to have one user sending large cookies over
the connection and block the stream for all other users for the time it takes
to send a huge 16kB of headers.

So MHS can help the proxy take the proper decision as well.

Best regards,
Willy
Received on Monday, 7 July 2014 08:54:49 UTC

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