I'm sorry, I'm not following you. What delay asymmetry are you refering to?
OWAMP does rely on accurate time stamps, see http://www.internet2.edu/performance/owamp/index.html If I have S1 and X1 synching to the same time reference (in this case, the same stratum 1 server), and I do one-way delay tests between S1 and X1, I'm expecting to find a valid measurement of the one-way delay, no? If you're talking about the asymmetry caused by NTP assuming the one-way delay to/from the clients is RTT/2, I'm aware of that error. And I will try to minimize it, e.g., using tunnels. On Friday, October 26, 2012 11:19:26 PM UTC+1, David Woolley wrote: > [email protected] wrote: > > > > > > > > Also, I don't want to use NTP to directly measure the one-way delay, I have > > OWAMP > > > > You can't stop it measuring the delay asymmetry! The trouble is you > > will not have any way to obtain that value, which will tend to cancel > > out the asymmetry measured by your primary tool, assuming it depends on > > accurate time stamps! > > > > > (more specifically perfSonar - http://www.internet2.edu/performance/pS-PS/) > > > to do that for me. > > > > > The page is a commercial type hype, not a technical overview of the > > algorithms used, but the only way I know of measuring one way delay is > > synchronise the clocks somewhat better than the acceptable measurement > > error, which you can't do if the synchronisation process is vulnerable > > to the effects of the same delay asymmetry. On Friday, October 26, 2012 11:19:26 PM UTC+1, David Woolley wrote: > [email protected] wrote: > > > > > > > > Also, I don't want to use NTP to directly measure the one-way delay, I have > > OWAMP > > > > You can't stop it measuring the delay asymmetry! The trouble is you > > will not have any way to obtain that value, which will tend to cancel > > out the asymmetry measured by your primary tool, assuming it depends on > > accurate time stamps! > > > > > (more specifically perfSonar - http://www.internet2.edu/performance/pS-PS/) > > > to do that for me. > > > > > The page is a commercial type hype, not a technical overview of the > > algorithms used, but the only way I know of measuring one way delay is > > synchronise the clocks somewhat better than the acceptable measurement > > error, which you can't do if the synchronisation process is vulnerable > > to the effects of the same delay asymmetry. On Friday, October 26, 2012 11:19:26 PM UTC+1, David Woolley wrote: > [email protected] wrote: > > > > > > > > Also, I don't want to use NTP to directly measure the one-way delay, I have > > OWAMP > > > > You can't stop it measuring the delay asymmetry! The trouble is you > > will not have any way to obtain that value, which will tend to cancel > > out the asymmetry measured by your primary tool, assuming it depends on > > accurate time stamps! > > > > > (more specifically perfSonar - http://www.internet2.edu/performance/pS-PS/) > > > to do that for me. > > > > > The page is a commercial type hype, not a technical overview of the > > algorithms used, but the only way I know of measuring one way delay is > > synchronise the clocks somewhat better than the acceptable measurement > > error, which you can't do if the synchronisation process is vulnerable > > to the effects of the same delay asymmetry. _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
