NTP Facts

Question 1

stratum levels.

Answer 1

The higher the stratum number, the lower it is in the stratum hierarchy and the less precedence it has in relation to other time providers with a lower number.
Stratum 0 is the highest level in the hierarchy. Stratum 0 is the authoritative time device itself, such as a GPS time source or atomic clock.
Stratum 1 is the server connected to the authoritative time device.
Stratum 2 providers synchronize time from stratum 1 providers.
Stratum 3 providers synchronize time from stratum 2 providers, and so on until the stratum level of 15 is reached (the maximum allowed).
Network hosts that are configured to use the NTP protocol to synchronize time function in the following roles:

An NTP time provider provides time to clients.
An NTP time client seeks time from a time provider.
A host can be an NTP time provider and an NTP time client at the same time, receiving time from one host while providing time to another host.
An NTP client can be configured to synchronize time from any NTP time provider. Several NTP configurations are commonly used:
In client/server mode, you can configure all NTP clients on the network to synchronize time with a public NTP source on the internet.
You can configure one internal host to be a master NTP time provider. It synchronizes time with a public time provider on the internet, creating an internal authoritative time source. You configure all other NTP clients on the network to get time from this host.
If the network is isolated from the internet, you can configure a master NTP time provider on one internal host to get time from its own internal clock. This creates an internal authoritative time source. All other NTP clients are configured to get time from this host.

Question 2

Event logging

Answer 2

Event logs should be sent to a central server where they can be easily viewed. Using NTP to tag each event with the same UTC time stamp is critical in establishing the order of events for troubleshooting and assigning priority.

Question 3

Time mismatch errors

Answer 3

There are some instances where a program will not function properly if the time is wrong.
Program and operating system updates can fail due to time mismatch.
Security certificates will suspect malicious behavior and block connections, if the computer time is off.

Question 4

Time drift

Answer 4

Time drift is when a system’s clock begins to get off by a few seconds or minutes.

Question 5

Slew method

Answer 5

If the time is off by only a few seconds, NTP adjusts the time a few milliseconds at a time to get it back on track. Slewing is a slower, methodical method of correcting the time, but the risk of problems occurring are much less.

Question 6

Slam method

Answer 6

If the time is off by more than a few seconds and slewing will take too long, NTP will hard reset the time. While this is a quick and immediate fix, slamming can cause some programs to not function properly.

Question 7

Skew

Answer 7

measures the difference (in hertz) between the actual frequency of a clock and its frequency to keep more accurate time.

Question 8

Dispersion

Answer 8

measures how scattered the time offsets (in seconds) are from a given time server.

Question 9

Drift

Answer 9

measures how quickly the skew of a clock changes (in Hertz per second)

Question 10

Jitter

Answer 10

refers to small, rapid variations in a system clock.