# AWS Time Sync, now with (limited) PTP support

**URL:** <https://community.ntppool.org/t/aws-time-sync-now-with-limited-ptp-support/3580>\
**Category:** Server operators\
**Created:** [October 29, 2024, 3:21am UTC](https://community.ntppool.org/t/aws-time-sync-now-with-limited-ptp-support/3580 "2024-10-29T03:21:12Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![n1zyy](https://sea2.discourse-cdn.com/flex016/user_avatar/community.ntppool.org/n1zyy/32/338_2.png) [@n1zyy](https://community.ntppool.org/u/n1zyy)\
**Post date:** [October 29, 2024, 3:21am UTC](https://community.ntppool.org/t/aws-time-sync-now-with-limited-ptp-support/3580/1 "2024-10-29T03:21:12Z")

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I happened across this the other day and thought I’d pass it along:

> **[Set the time reference on your EC2 instance to use the local Amazon Time Sync...](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/configure-ec2-ntp.html#ptp-hardware-clock-requirements)**
>
> Set the time reference on your Amazon EC2 instance to use the local Amazon Time Sync Service or connect to the PTP hardware clock.

(I worry this makes me sound like an Amazon shill. In actuality, using AWS makes me tear my hair out most of the time, but this one bit is kind of cool.)

It’s only in limited regions, and on limited instance types (for now?), but AWS is starting to support PTP with its existing Time Sync service. For grins I spun up the cheapest compatible instance in Malaysia, compiled the driver, and chrony saw it as a stratum 0 PHC source. It is indeed pretty stable:

```plaintext
chronyc> sources
MS Name/IP address Stratum Poll Reach LastRx Last sample
===============================================================================
#* PHC0 0 0 377 1 +25ns[+27ns] +/- 5031ns
^- sgsin3-ntp-002.aaplimg.c> 1 10 377 368 -36ms[-36ms] +/- 39ms
^- 144.126.242.176 2 10 377 24m -748us[-744us] +/- 9011us

```

```plaintext
chronyc> tracking
Reference ID : 50484330 (PHC0)
Stratum : 1
Ref time (UTC) : Tue Oct 29 02:49:05 2024
System time : 0.000000003 seconds fast of NTP time
Last offset : +0.000000009 seconds
RMS offset : 0.000000012 seconds
Frequency : 1.484 ppm fast
Residual freq : +0.000 ppm
Skew : 0.004 ppm
Root delay : 0.000010000 seconds
Root dispersion : 0.000001281 seconds
Update interval : 1.0 seconds
Leap status : Normal

```

Incidentally, it seems that this makes me the only public stratum 1 NTP server in Malaysia?

It would be interesting if they continue to roll this out globally, because there are some regions that seem like they could benefit from having more/any stratum 1s available. A major downside is that AWS bandwidth is outrageously expensive, so I currently have this new instance in the pool at 512kbps since I’ll pay $0.108/GB for outbound traffic. (I actually added a cheap VPS to the pool pointing at this AWS instance with a greater bandwidth setting to try to soak up some of the traffic. There were only three IPv4 servers when I started, and I’m not sure how reliably the pool bandwidth proportioning works when there are fewer than 4 instances to go around.)

I’m not sure there’s a need for dozens of people to do the same, but I thought I’d pass this along because I can’t be the only person here to whom this is interesting.

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**Author:** ![Badeand](https://avatars.discourse-cdn.com/v4/letter/b/c2a13f/32.png) [@Badeand](https://community.ntppool.org/u/Badeand)\
**Post date:** [October 29, 2024, 4:08pm UTC](https://community.ntppool.org/t/aws-time-sync-now-with-limited-ptp-support/3580/2 "2024-10-29T16:08:47Z")

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Where does aws get their time from though? Safe to assume they’re highly accurate?

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<div class="post-metadata">

**Author:** ![n1zyy](https://sea2.discourse-cdn.com/flex016/user_avatar/community.ntppool.org/n1zyy/32/338_2.png) [@n1zyy](https://community.ntppool.org/u/n1zyy)\
**Post date:** [October 30, 2024, 11:01pm UTC](https://community.ntppool.org/t/aws-time-sync-now-with-limited-ptp-support/3580/3 "2024-10-30T23:01:03Z")

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They don’t provide copious details, but [an earlier Time Sync blog post](https://aws.amazon.com/blogs/aws/keeping-time-with-amazon-time-sync-service/) described “a fleet of redundant satellite-connected and atomic clocks in each region.”

In [their blog post about PTP support](https://aws.amazon.com/about-aws/whats-new/2023/11/amazon-time-sync-service-microsecond-accurate-time/), they reference “GPS-disciplined reference clocks” being “within microseconds of UTC.”