[Freeswitch-users] FreeSWITCH, NTP daemon and clock drift

[Peter Olsson]

Tony, I tested this on Windows, and found a few glitches (some are probably there for Linux as well). Could you please check out FS-4387 for a proposed patch.

/Peter

-----Ursprungligt meddelande-----
Från: freeswitch-users-bounces at lists.freeswitch.org [mailto:freeswitch-users-bounces at lists.freeswitch.org] För Anthony Minessale
Skickat: den 4 juli 2012 00:16
Till: FreeSWITCH Users Help
Ämne: Re: [Freeswitch-users] FreeSWITCH, NTP daemon and clock drift

My first instinct is to say: don't use boxes with unreliable timing in them since if they can't keep time, the precision for audio could be even worse.
But,

Its not an unreasonable request

give this param a try in latest git:

enable-use-system-time in switch.conf.xml

the status uptime should still be right but the timestamps etc will follow system time.

use at your own risk



On Tue, Jul 3, 2012 at 2:36 PM, Steven Ayre <steveayre at gmail.com> wrote:
> Anthony,
>
> There's previously been a discussion captured on 
> http://wiki.freeswitch.org/wiki/Clock regarding the internal clock 
> time FS keeps.
>
> Currently FreeSWITCH uses the monotonic clock and ignores system time. 
> On machines where the time is very unreliable, NTP isn't in use and 
> the sysadmin is changing the time manually or by ntpdate the system 
> time can make large jumps - and I can indeed see the reasoning that 
> having FS use its own clock on these systems is more reliable as it 
> prevents billing time being lost because of a large clock jump.
>
> However, on systems correctly running ntpd that have clock drift the 
> system time will constantly be being corrected and won't experience 
> large jumps and in these cases the system time will be more accurate 
> than FreeSWITCH's internal time.
>
> On such systems although FreeSWITCH might not be losing billing 
> seconds from clock jumps (which shouldn't normally happen) the clock 
> drift will mean that there is also that clock drift present in 
> FreeSWITCH's CDRs - and these could conceivably cause billing disputes 
> where a customer's CDRs do not have the same times because their times 
> are more accurate than FS's due to that clock drift. This is unlikely 
> to be large enough to affect billed minutes much, but could put a 
> large number of calls on the wrong billing rate (eg if FS's internal 
> time in the CDRs identifies calls as on a peak rate when the customer 
> believes it is on an offpeak rate). On a badly drifting system over a 
> month on a large volume of calls that could become a noticeable discrepancy.
>
> Obviously there is the sync_clock option, but it seems you shouldn't 
> need to run that frequently (and would that cause any sideeffects?) 
> Running it infrequently would cause the same time-jumping behaviour 
> FS's internal time was designed to avoid, and sync_clock_when_idle 
> isn't possible on busier systems.
>
> On systems running ntpd perhaps it would be worth adding an opt-in 
> option that lets FreeSWITCH use the system time and rely on ntpd (but 
> keeping the present behaviour as the default)?
>
> Your thoughts please...
>
> Warm regards,
> -Steve
>
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--
Anthony Minessale II

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