https://labs.ripe.net/Members/romeo_zwart/LuigiCorselloAtlasanchorvirtualisa...
nice masters level work, which i presume it was. of course, the devil is in the details, and he seemed to be dealing with a lot of devils. for me, interested in timing, the following was the most disappointing: The "accurate timekeeping" requirement, for the way it was defined, has no unconditional winner. Carefully configured NTP with stable peers is the minimal condition for stable timekeeping, however a ceiling of "1ms" set during the research may be too strict to be respected at all times by a virtualization technology and maybe even by physical PC hardware. while he seemed to have explored the standard kvm hack of the guest booting with no-kvmclock while running ntpd in the guest (for which the net of a thousand lies makes a very clear case), Section 4.3.3. KVM does not make clear that this configuration is what was evaluated. in general, i worry that he discovered ntp during the project and may not have configured the DUTs as well as they could have been. the researcher was brutally honest about details, limits, what was unexplored, ... you gotta love The role and importance of the Network Time Protocol to guarantee an accurate timekeeping has been progressively "discovered" during the analysis phase of this research. when ntp's precision is not really all that great, hence the gps clocks for ttm. i would greatly love to see this researcher explore ttm time precision and accuracy before ttm is retired, so we can compare to previous analyses. i was worried by In fact, the first TTM node for time monitoring (tt97.ripe.net) resided in a different VLAN than the POC and had an average delay of about 1100μsec! That was certainly not good enough to measure sub millisecond time accuracy and was replaced by tt999.ripe.net installed in the same VLAN as the POC. ntp is designed to be pretty insensitive to rtt. so this either scares the hell outta me about ttm, is a misunderstanding, or miscommunication. i would love to see more analysis of this. side note: it would have been nice if he had run openvz and kvm on something less paleolithic than centos. but my compliments to the researcher and to the ncc for funding him. useful work. randy