Jitter of spreading spectrum clock

[hmsheng]

(1)How to define the period jitter, cycle to cyle jitter (or short-term jitter), and accumulated jitter (or long-term jitter) of a spreading spectrum clock like following attached figure?
(2)Which one is important of period jitter, C-C jitter, and ACC jitter for spreading spectrum clock?

Another problem about jitter simulation:

 

[layes2]

may be you can see the same point of period

 

[hmsheng]

The period jitter and accumulated jitter should be large because of the time-varying frequency in the preading spectrum clock. But the cycle-to-cycle jitter can be kept small because the spreading frequency is much less than the clock frequency. The cycle-to-cycle jitter is the right parameter for calculating the margins for set-up time and hold-on time. So, I think only the cycle-to-cycle jitter is meaningful for the spreading spectrum clock. Am I right?