Hi Randy, On 13/09/16 01:59 , Randy Bush wrote:
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.
Thanks for taking the time to review. I will forward your comments, I am sure the researcher will be pleased with your constructive criticism. [...]
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.
This is a misunderstanding and probably only reflects a very early view of the researcher on the topic. I don't believe it was intended to comment on the quality of the TTM mechanism. :) WRT you other question about more work along these lines on TTM. I think it's unlikely we will follow this up further. The researcher has moved on the greener fields in the mean time and a lot of work on TTM has been done in the early 2000's and before, see e.g. [1]. Although that particular reference is not specifically looking TTM accuracy.
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.
Thanks for that comment. I will pass it on. :)
randy
[1] http://www-nas.et.tudelft.nl/people/Piet/papers/PAM2002.pdf