Re: [chrony-users] Interop with NTP version 1 and 4 clients

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On Tue, 19 Feb 2013, Benny Lyne Amorsen wrote:

tir, 19 02 2013 kl. 08:31 -0800, skrev Bill Unruh:

On Tue, 19 Feb 2013, Benny Lyne Amorsen wrote:

Chrony is working very well as an NTP server (not a stratum 1 of

Chrony works perfectly well as a stratum 1-- just use refclock of say a gps
pps source.

I didn't realize that chrony had PPS support. Excellent.

What version of chrony are you using?


No idea about this. As far as I know sntp uses exactly the same packets as
does full ntpd. get a better app.

Yes well, getting a better app is an uphill battle. LG phones send SNTP
only. tcpdump shows the packets as NTPv1, and chrony ignores them.

As I said, sntp is NOT version 1. SNTP is defined in both the V3 and V4 rfcs
and use the same packets. It is ludicrous that the lg phones are sending out
packets whith V1 in them. But if you wanted to try, you could change NTP_MIN_COMPAT_VERSION to 1 and NTP_VERSION to 4 in ntp_core.c of chrony I am
not sure that this will not break things, but it should be easy to try doing
so and see if stuff breaks.

Anyway again, in both cases it is bugs in the phone software that is giving
you trouble and you are either going to have to write them off, or try
contorting chrony to satisfy what they want. It is of course not at all clear
that this will break support for other phones.

As far as I can see, the difference between the ntpd versions (1 2 3 4) is not
in the packets that are  exchanged, but in the way the data is massaged in order to
discipline the local clock.

Here is the tcpdump of a client indicating NTPv4 but receiving an NTPv3
answer. The client then proceeds to ignore that answer and repeats the

What software is being used by the client?

Good question. Aastra phones are the clients. They work with (and are
probably only tested against) ntp 4.2.x.


William G. Unruh   |  Canadian Institute for|     Tel: +1(604)822-3273
Physics&Astronomy  |     Advanced Research  |     Fax: +1(604)822-5324
UBC, Vancouver,BC  |   Program in Cosmology |     unruh@xxxxxxxxxxxxxx
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