Re: Why don't we talk about segments/objects instaead of layers? Re: Lost Layer?
Detlef Bosau <[email protected]> Tue, 18 Feb 2014 20:39:44 +0100
| Newsgroups | gmane.network.end2end |
|---|---|
| Message-ID | <[email protected]> |
Am 18.02.2014 19:00, schrieb [email protected]: > 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 change.) 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 with formulae. And that's exactly what you often refuse when being done by others ;-)