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RE: HTTP 1.1 Pipelining

From: Tim.Greenwald <tim.greenwald@wamu.net>
Date: Mon, 04 Aug 2003 08:52:11 -0500
To: Ian Clelland <ian@veryfresh.com>, Mike Dierken <mdierken@hotmail.com>
Cc: www-talk@w3.org
Message-id: <MAENIHPCMNELNPHOJIGCOEBGCBAA.tim.greenwald@wamu.net>

Keep-alive has been replaced with persistent connections. This works great
because it doesn't make sense to open/close connections for every object.

Pipelining, as I understand it, opens a connection from a client and sends
request1, request2, request3... end. The problem as I see it is that the
server services these requests sequentially, in the order received. So in
HTTP 1.0 a client could open connection, send request1, and open a second
connection, send request2,... Then the server can process these multiple
connections and requests in a multi-threaded scenario. The bad side of this
is the opening/closing of connections. The good side is the independent
handling of those requests.

Regards,
Tim Greenwald

"You can't manage what your not measuring"

-----Original Message-----
From: www-talk-request@w3.org [mailto:www-talk-request@w3.org]On Behalf
Of Ian Clelland
Sent: Saturday, August 02, 2003 6:35 PM
To: Mike Dierken
Cc: www-talk@w3.org
Subject: Re: HTTP 1.1 Pipelining



On Fri, Aug 01, 2003 at 09:30:59PM -0700, Mike Dierken wrote:
>
> Is pipelining the same as 'keep-alive'?
> I thought it was something different...
>
> ----- Original Message -----
> From: "Tim.Greenwald" <tim.greenwald@wamu.net>
> > I would be interested in comments regarding the trade-off of using
> > pipelining. My thoughts on this are that it is great because it relieves
> the
> > burden on the server of having to open a TCP connection for each request
> for
> > an object but the trade-off is that the requests have to be
sent/received
> in
> > order. This seems to me to override the benefits of multi-threading. If
I
> > was to send multiple GETs at the same time I would open multiple
> connections
> > but the requests could be processed concurrently.

It's a similar concept -- Keep-Alive was an artifact of HTTP/1.0 which
was removed in HTTP/1.1. In 1.1, the default behaviour is to keep
connections open for some time to accept further requests, unless a
'Connection: close' header is sent.

In response to the original question, I don't think it's really a
tradeoff at all -- you can optimise a client's performance by using
request pipelining in conjunction with multiple requests.

I don't think it's uncommon for a web client to open one connection to a
server to get a document, then open half a dozen more connections to get
the related images / style sheet, and then keep all of those connections
open. When the user clicks a link to another document on the same
server, the connections are all still open, so the second document can
be retreived even faster.

Ian Clelland
<ian@veryfresh.com>
Received on Monday, 4 August 2003 10:20:20 GMT

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