Topic

asymmetric latency

A collection of 5 issues

DOCSIS 3.1 and NTP

Spectrum upgraded my area to DOCSIS 3.1 to offer 1G/40M service. I believe they have it configured for 1.7Gbit shared downstream (using DOCSIS 3.1) and ~100Mbit shared upstream (sharing the legacy DOCSIS 3.0 upstream channels). This is unverified because the modem (a Technicolor TC4400-AM) has

Stratum 2 NTP over a Cable Modem

Goals I have a Stratum 1 NTP server at home, and ideally I'd like to join the ntp pool as a server. The problem is, my home connection isn't up to this task. My IP is dynamic, there's an asymmetric latency built in, and

Measuring Asymmetric latency via NTP, part 3

Part 1 [https://blog.dan.drown.org/measuring-asymmetric-latency-via-ntp/], Part 2 [https://blog.dan.drown.org/measuring-asymmetric-latency-via-ntp-part-2/] Varying round trip times Asymmetric latency changes NTP's calculated clock offsets. What do the offsets look like when two clocks are in sync (or always within ~200us) and the latency varies? SMQ

Measuring Asymmetric latency via NTP, part 2

See the first part for the math [https://blog.dan.drown.org/measuring-asymmetric-latency-via-ntp/] Let's use a third party (stratum 2) observer to compare the stratum 1 NTP clocks. Round trip times First, a graph of the $rtt times from the third party to various stratum 1 NTP clocks.

Measuring Asymmetric latency via NTP

Goal Learn more about the latency characteristics of my cable connection. Starting point I have a stratum 1 NTP server at home. Below is a graph of its performance. The offset between the GPS clock and the server's clock is in red. The two clocks are within +/-