Maarten Wiltink wrote: > "Unruh" <[EMAIL PROTECTED]> wrote in message > news:[EMAIL PROTECTED] > [...] >>> What should I be doing to get 20 us? Buy all new computers with >>> gigabit Ethernet? >> I suspect buying better switches. And it looks to me like you should >> definitely NOT go to gigabit Ethernet if you want good timing. > > Seeing as how gigabit Ethernet uses jumbo frames to reach decent > throughput, I suspect it's subject to higher jitter at the network > level. NTP frames are short, but if it's contending with a large > download, there will be a relatively large unpredictable delay on > the line.
I wrote a very similar msg, then I started to consider the math: 100 Mbit uses 1.5 kB packets, while Gbit jumbo frames are typically 9 kB, right? The thing is that as long as the jumbo frames are less than 10 times the size of regular packets, the wire will be busy for a shorter time than for a 1.5 K packet on 100 Mbit! Hybrid interrupt/polled hardware & drivers are a much more likely culprit: If the hardware waits a little bit before interrupting, hoping to be able to bunch up several packets in a single task, then jitter will suffer badly. Terje -- - <[EMAIL PROTECTED]> "almost all programming can be viewed as an exercise in caching" _______________________________________________ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
