The MPLS WG Archive

[Eric Gray <eric.gray@sandburst.com>]

David,

    You can't exactly do ATM style QoS over non-ATM media.

    The thing that allows an ATM switch to contemplate delay
variation separately from delay is the fact that ATM switches
switch data in fixed size chunks.  When the size of data chunks
can vary, the only practical way to control delay variation is to
try to control delay.  Therefore, with IP packets on non-ATM
media, you can't even begin support two knobs for delay and
delay variation.  So why would you undertake to add complexity
by trying?

--
Eric Gray

You wrote:

> Eric Rosen wrote:
> >
> > I think this is a good time to repeat a remark that Luca Martini
> > made at the PWOT BoF in Minneapolis:
> >
> >         If people wanted the ATM service model, we'd all be run-
> >         ning ATM to the desktop now.
>
> That's incredibly oversimplified.  I'm rather surprised to see you take
> such a cheap shot in this group.
>
> There are a great many reasons why ATM hasn't displaced Ethernet on
> people's desktops, including the price of switch ports and a routing
> protocol that would have a hard time scaling to the size of the
> internet.
>
> The fact that most people don't run ATM to their desktop doesn't mean
> that ATM-style QoS wouldn't be appreciated over non-ATM media.
>
> -- David