Re: Re: Firefox users - please note....

[James Fidell <james@xxxxxxxxxxxx>]

Quoting mark_harrison_uk2 (mph@xxxxxxx):
>
> --- In ukha_d@xxxxxxx, "J." <chemically_enhanced@h...>
wrote:
> >
> > Unless it happens to be your server that people are accessing.
most
> > servers ar throttled to handle a mximum number of request at any
one
> > time,  If you put your settings at 30 - 40 and everyne else does
it
> > acts as a denial of service to other users as the server will
just
> > return a 503 http response. play nicely!
> > #
> > </rant mode off>
> >
> > J.
>
> Have you seen this happen? The discussion lists have been full of
> people warning that "this could happen", but I've not yet
seen anyone
> actually demonstrate that it HAS happened.

My understanding of what happens is as follows:

Normally when you request a web page, your browser opens a single
connection to the webserver and sequentially requests all the elements
of the page from that single connection.

What the "pipelining" stuff appears to do is to tell Firefox to
open
multiple concurrent connections to the webserver at the same time and
"multiplex" all its requests down those connections.

>From the webserver's point of view this means that it will be trying to
serve lots of different files to you at once, as opposed to one after
the other.  Webservers however usually have a fixed limit on the number
of concurrent connections they'll allow in total, so if enough people
are opening lots of connections to the same server at the same time,
the server will start returning a "too busy" message when there
are
fewer users than if everyone just opened one connection at a time.

One might think that this shouldn't actually be a problem, because
although you're opening multiple connections, you're requesting fewer
files from each one and therefore not using the connection for as long.
However, it's usual once a client has connected to a webserver to keep
the connection open for a while in case it needs to be used again,
because doing so requires less resources than closing the connection and
re-opening it later.  So, even after you've grabbed the web page you
may still be using resources on the webserver.

This may result in an effective denial of service for users of the
website, depending on how busy it is. If that does turn out to be
the case, I'd expect the server administrators might reconfigure the
server to restrict the number of concurrent connections from any given
client and/or reduce the time that the connection is kept alive. I
shouldn't be surprised if that resulted in people who are using the
pipelining finding that their browser performance has returned to
it's pre-pipelining levels and those that don't use it finding that
theirs has reduced further. If it becomes a serious problem I guess the
developers will just remove the settings from future releases of the
browser.

All this is theory though.  What's really required is some empirical
evidence, which seems unlikely to be forthcoming given that it'll be
hard work to collect.

James