On 2013-01-28, Rob <nom...@example.com> wrote: > no-...@no-place.org <no-...@no-place.org> wrote: >> On 28 Jan 2013 09:57:00 GMT, Rob <nom...@example.com> wrote: >> >>>There will be the extra complication that a UMTS connection goes into >>>a "sleep mode" when there is little or no traffic. To "wake it up" >>>you need to send about 4 packets/second for some time. This is a >>>very typical pattern on a UMTS connection: >>> >>>ping -i1 172.31.32.18 >>>PING (172.31.32.18) 56(84) bytes of data. >>>64 bytes from (172.31.32.18): icmp_seq=1 ttl=127 time=461 ms >>>64 bytes from (172.31.32.18): icmp_seq=2 ttl=127 time=377 ms >>>64 bytes from (172.31.32.18): icmp_seq=3 ttl=127 time=390 ms >> ........ >>>64 bytes from (172.31.32.18): icmp_seq=9 ttl=127 time=246 ms >>>64 bytes from (172.31.32.18): icmp_seq=10 ttl=127 time=144 ms >>>64 bytes from (172.31.32.18): icmp_seq=11 ttl=127 time=50.8 ms >>>64 bytes from (172.31.32.18): icmp_seq=12 ttl=127 time=52.2 ms >>>64 bytes from (172.31.32.18): icmp_seq=13 ttl=127 time=102 ms >>>64 bytes from (172.31.32.18): icmp_seq=14 ttl=127 time=50.4 ms >>>64 bytes from (172.31.32.18): icmp_seq=15 ttl=127 time=51.4 ms >>>64 bytes from (172.31.32.18): icmp_seq=16 ttl=127 time=52.4 ms >>>64 bytes from (172.31.32.18): icmp_seq=17 ttl=127 time=47.6 ms >>>64 bytes from (172.31.32.18): icmp_seq=18 ttl=127 time=50.1 ms >>>64 bytes from (172.31.32.18): icmp_seq=19 ttl=127 time=51.4 ms >>>64 bytes from (172.31.32.18): icmp_seq=20 ttl=127 time=47.4 ms >>> >>>As you can see, totally unsuitable for accurate time calibration. >> >> Would I likely get better results if I advised my users to connect to >> broadband wi-fi if possible and I use that instead of 3G data? > > WiFi has the same problem on a slightly smaller scale. > With WiFi the pingtime jitters by 50 ms or so.
But what matters is not the ping time jitter, but the assymetric travel time jitter. On wifi that is nearer 1 -10 ms _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions