[e2e] Why don't we talk about segments/objects instaead of layers? Re: Lost Layer?

Andrew Mcgregor andrewmcgr at google.com
Tue Feb 18 15:54:12 PST 2014

I had this in another tab:

We have some really good models, that paper is the tip of a really large
iceberg.  The hard thing is shoehorning them in to a legacy protocol's
header fields, and then getting agreement across some large number of
administrative domains to actually use the resulting protocols.

On 19 February 2014 06:39, Detlef Bosau <detlef.bosau at web.de> wrote:

> 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
> 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 ;-)

Andrew McGregor | SRE | andrewmcgr at google.com | +61 4 1071 2221

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