[cube13]

>Well if it is measured at the 1-second or 1-millisecond level, yes the exchanges are in compliance. At the 100-microsecond, 10-microsecond and nanosecond level, perhaps the exchange is in compliance at the 50th percentile.

And once you hit the <1 millisecond level, it's hard to even get reliable measurements, which makes compliance for "same time delivery" really really freaking hard.

Keep in mind, when you're talking about the nanosecond level, you're at the point where the length of cabling between the systems matters.

Sure, there's a lot of new tech coming out, especially with using GPS to synchronize clocks, but it's still a major issue.

[itchyouch]

It's a hard problem, but it's not insurmountable. Most places are getting these measurements by using PTP with hardware timestamping. Solarflare has NIC offerings where the packets are hardware timestamped on the wire regardless of the queueing that occurs on the internal socketbuffer with that data being available through several special metachannels.