[e2e] Network level qos support for web services

[Sridhar Ramesh]

On Sun, 17 Oct 2004 15:44:58 -0700, Christian Huitema
<huitema at windows.microsoft.com> wrote:
> > Are there (applications using, requirements for, ...) web services out
> > there which really DO require network QoS (i.e. have strict delay
> bounds,
> > require throughput guarantees... something like this)?
> 
> In practice, there are three kinds of networks: those that have enough
> capacity for the desired application, those that don't, and those that
> are in between. QOS schemes are only useful in the latter case, when the
> network almost has enough capacity for the application's demand, but not
> quite. They are useless if the network is to narrow: no amount of QOS
> will enable HDTV on a narrowband modem line. They are also useless if
> the network has enough capacity, since they only serve there to make the
> network more complex.
> 
> QOS is not the only possible response in the "in between" state. If the
> network has "almost enough capacity", one can generally redesign the
> application to consume slightly less resource, e.g. use more
> compression. If the application is valuable, there will be incentives to
> increase the network capacity so it will always work.
> 
> The "in between" case is a transient state, and the domain of
> applicability of QOS solutions is very narrow.
> 
> -- Christian Huitema
> 

I have a problem with the part "enough capacity for the application's
demand". Applications like file transfer typically do not come with a
fixed demand but try to fill out whatever the network gives them
(being built over TCP which does its probing and flow control).
By assigning their packets a lower priority than those of voice
or video with which they may be sharing network resources, we
could throttle them down when the higher priority apps are active, right ?
Who really cares if the file download takes a couple of minutes
longer because we were making a long distance VoIP call ?

Regards,
Sridhar