What causes clock drift?
The rate of drift depends on the clock’s quality, sometimes the stability of the power source, the ambient temperature, and other subtle environmental variables. Thus the same clock can have different drift rates at different occasions.
What is the difference between NTP and NTPD?
The NTP algorithm includes information to allow you to calculate and fix the drift in your server’s clock. NTPD includes the ability to use this to keep your clock in sync and will run more accurately than a clock on a computer not running NTPD. NTPD will also use several servers to improve accuracy.
What’s the difference between NTP and normal smear interval?
During the smear interval the time provided by smearing NTP servers differs significantly from UTC, and thus from the time provided by normal, non-smearing NTP servers. The difference can be up to 1 second, depending on the smear algorithm.
What are the pros and cons of NTP smearing?
Here’s an excerpt: Pros and Cons of the Smearing Approach The disadvantages of this approach are: * During the smear interval the time provided by smearing NTP servers differs significantly from UTC, and thus from the time provided by normal, non-smearing NTP servers. The difference can be up to 1 second, depending on the smear algorithm.
How does leap second smearing work in NTP?
Due to the reasons mentioned above, some support for leap smearing has recently been implemented in ntpd. This means that to insert a leap second an NTP server adds a certain increasing “smear” offset to the real UTC time sent to its clients, so that after some predefined interval the leap second offset is compensated.
Is there a fix for leap second in NTP 4.2.8?
In 4.2.8 the leap second code was rewritten and some enhancements were introduced, but the resulting code still showed the behavior of 4.2.6, i.e. ntpd with -x would still step the time. This has only recently been fixed in the current ntpd stable code, but this fix is only available with a certain patch level of ntpd 4.2.8.