[EMAIL PROTECTED] wrote: > I've got two (x86_64 Linux) machines between which I need to > determine the relative time difference. The problem is, the > machines are not directly connected and only one is connected to the > Internet. > > The topology looks like this: > > box_1 <--VPN--> box_common <--LAN--> box_2 > > It's not so important that box_1 and box_2 are synced, but that > their time difference is accurately measured. > > So, box_1 and box_common sync via NTP to (different) public stratum > 2 NTP servers. box_2 syncs to box_common. > > I wrote a simple program to try an determine the time difference > between box_1 and box_2. The program works like this: > > box_1 and box_2 run the program in "server" mode; when queried, the > server program calls gettimeofday() and returns the timeval result > via UDP. > > box_common runs the program in "client" mode. client mode does the > following: > > - record the current time via gettimeofday() as t1 > - send a UDP packet to the remote server > - wait for the UDP response (i.e. the remote machine's actual > time) > - record the time of the UDP response as t2 > - define "remote calculated time" as the midpoint between t1 and > t2 > - calculate the difference between "remote calculated time" and > the actual remote time as provided by the UDP response; call > this t_d > > Once I've done the above for box_1 and box_2, I subtract t_d1 and > t_d2. > > I'm just looking for some feedback on my approach: is it valid (i.e. > am I overlooking something?), are there better approaches, etc? >
What do you think that NTP does? and why don't you think that after 20+ years of engineering that it doesn't do a much better job? Danny _______________________________________________ questions mailing list [email protected] https://lists.ntp.isc.org/mailman/listinfo/questions
