What you want from the probe is predictability in the form of minimal jitter and possibly some calibration (to equate latency). IF the Turris people can run the Atlas code with some sort of real-time scheduling then it is going to be OK as a probe. Can they? If it is a process competing with whatever else the router might be doing at the time then I agree, it wouldn’t be suitable as a probe for things that involve precise time measurements, although they could still run the set of measurements for which precise timing is not necessary (routing, DNS, etc). In the Atlas probe all software is under control of one party and *I guess* doesn’t interfere with the rest of the software running on them. The criteria should be reproducibility of the experiment, not whether it is a VM or something else. Just my opinion Joao
On 05 Dec 2015, at 17:27, Gert Doering <gert@space.net> wrote:
On Fri, Dec 04, 2015 at 11:30:34PM +0100, Daniel Suchy wrote:
I don't fully agree here. There're always so many things, which may involve measurement realiability just on first from the probe. You always believe, that "hardware" probe is more reliable. Not, it isn't - current probe itself is quite cheap piece of not-so-powerfull hardware. And if someone want's to trick measurement, he can - there're so many ways. You don't have any kind of control on network behind the probe - and that's more important part in terms of reliable measurements...
The thing is "we perfectly well know the characteristics of the measuring device". Everything deviating from the norm will be caused by the network, not "something in the VM environment".
Many thing are going virtual around us (even on high-end routing platforms). Virtualised probe can be more reliable in terms of computing power compared to small TP-Links & so-on.
Computing power is totally unimportant as compared to reproduceability of a given measurement on a given probe.
Of course a VM is more powerful than either of these probes, but does this make it more suitable to be part of Atlas? I say no, because for a measurement platform, "raw power" is not the key issue.
Gert Doering -- NetMaster -- have you enabled IPv6 on something today...?
SpaceNet AG Vorstand: Sebastian v. Bomhard Joseph-Dollinger-Bogen 14 Aufsichtsratsvors.: A. Grundner-Culemann D-80807 Muenchen HRB: 136055 (AG Muenchen) Tel: +49 (0)89/32356-444 USt-IdNr.: DE813185279