[e2e] Why don't we talk about segments/objects instaead of layers? Re: Lost Layer?
detlef.bosau at web.de
Tue Feb 18 11:39:44 PST 2014
Am 18.02.2014 19:00, schrieb dpreed at reed.com:
> Well, if you compare economics (barely a science, but only when it actually allows data to disconfirm hypotheses, which almost never happens) with queueing theory and control theory, I cannot refute you.
You cannot refute queueing theory and control theory. (Listen to
yourself ;-) You quite often do EXACTLY this ;-))
However, the question is whether these two apply to computer networks.
You told us more than once that we have hardly realistic models for user
behaviour. (We know how to model Monsieur Poisson and Andrej Andrejewich
Markov - however, how do we model the rest of the world?) Than all these
theories assume potentially infinite buffers.
And for control theory: If you really want to apply system theory here
(you did not appreciate my thoughts in this direction in some off list
discussions) you are in the need of a model.
No problem: The packets are the "energy": packets on the fly (links) are
"kinetic energy", packets in queues are "power", the state variables are
buffer queues (which are limited in real life) and links (the transport
capacity of which is HIGHLY volatile as we discussed in many details) ,
in addition: Which state variables are to be taken into consideration?
(Of course the links and buffers along the path, unfortunately, this may
VJ even talks about a "Ljapunov function" which is actually ludicrous.
The concept of Ljapunov stability intends wo make a system behave close
to a given trajectory in state space. How do we apply this concept to a
flow where we cannot even agree upon the state variables in charge.
Yes, you cannot refute queuing theory and control theory.
But applying these to a model, where they do not apply is hand waving
And that's exactly what you often refuse when being done by others ;-)
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