Dan Drown

SB6183 vs DG1670A latency

See also: SB6183 dropping IPv6 traffic [https://blog.dan.drown.org/sb6183-dropping-ipv6-traffic/] Comparing latency in cable modems: SB6183 (16 channel DOCSIS 3 modem only) vs DG1670A (16 channel DOCSIS 3 modem+router combo, in bridge mode) Arris DG1670A Average latency of 100 ICMP echo replies to the default gateway: 20.

Beaglebone Black NTP/GPS Server, Temperature Compensation part 2

See the Part 1 of Temperature Compensation [https://blog.dan.drown.org/beaglebone-black-ntpgps-server-temperature-compensation/] or the hardware setup [https://blog.dan.drown.org/beaglebone-black-ntpgps-server/] Overview In part 1, I did a trial run of chrony's temperature compensation and got a pretty good result. In this part, I collected more

Beaglebone Black NTP/GPS Server, Temperature Compensation part 1

See also: The hardware/software setup [https://blog.dan.drown.org/beaglebone-black-ntpgps-server/] or part 2 [https://blog.dan.drown.org/beaglebone-black-ntpgps-server-temperature-compensation-part-2/] Overview Chrony (the NTP server software) has temperature compensation built in, using a quadratic forumla to estimate the effect of temperature changes have on the speed of the local

Beaglebone Black NTP/GPS server

Goals I wanted to experiment with using temperature measurement to augment a NTP stratum 1 server. I started with a very similiar setup to this one [https://web.archive.org/web/20131209092059/http://the8thlayerof.net/2013/12/08/adafruit-ultimate-gps-cape-creating-custom-beaglebone-black-device-tree-overlay-file/] . [Edit: the8thlayerof.net is gone, link changed to archive.org]. This

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 +/-

Time Warner 300/20 service

Before (50M/5M) After (300M/20M) Other notes DG1670A Firmware Version was updated from 8.0.89 to 8.0.120. SW_REV: 8.0.120.SIP.PC20.TW IPv6 $ iperf -f m -i 1 -V -c 2605:6000:x:x -r ------------------------------------------------------------ Server listening on TCP port 5001 TCP

New Time Warner router: Arris DG1670A

See also: Comparison of the Arris SB6183 vs Arris DG1670A [https://blog.dan.drown.org/sb6183-vs-dg1670a-latency/], and SB6183 dropping IPv6 traffic [https://blog.dan.drown.org/sb6183-dropping-ipv6-traffic/] As part of TWC's upgraded speeds (300M/20M coming in August), I needed a 16x4 channel DOCSIS 3.0 modem. Since