The MPLS WG Archive

[David Charlap <david.charlap@marconi.com>]

Eric Gray wrote:
> 
>     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?

Variable-size frames don't make it impossible.  It just means you are
forced to work with a coarser granularity (defined by your configured
MTU size.)

-- david