On 28 May 2014 20:31, "David Collier-Brown" <davec-b@rogers.com> wrote:
>
> On 05/28/2014 11:33 AM, Jonathan Morton <chromatix99@gmail.com> wrote
> > It's a mathematical truth for any topology that you can reduce to a black box with one or more inputs and one output, which you call a "queue" and which *does
> not discard* packets.  Non-discarding queues don't exist in the real
> world, of course.
> >
> > The intuitive proof is that every time you promote a packet to be transmitted earlier, you must demote one to be transmitted later.  A non-FIFO queue tends to increase the maximum delay and decrease the minimum delay, but the average delay will remain constant.
>
> A niggle: people working in queuing theory* make the simplifying
> assumption that queues don't drop. When describing the real world, they
> talk of "defections", the scenario where a human arrives at the tail of
> the queue and "defects", either to another queue or to the exit door of
> the store!

I think my description of the black box is still valid: a "defection" must imply a second output from the box, otherwise it will appear as either a reordering (preserving the property) or a discard.

- Jonathan Morton