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Quantitative Finance · शब्दावली

Boundary clock, transparent clock क्या है?

अन्य नाम: boundary clock · transparent clock

Definition 4.9 Networks, Hardware and Trading Infrastructure · अध्याय 4 — Time Synchronisation

A boundary clock is a network device with its own clock that is a PTP slave on one port and a master on its others: it ends one exchange and starts new ones, so that no PTP message crosses it. A transparent clock forwards PTP messages and adds to a correction field in each the time the message spent inside the device (its residence time), which the endpoints subtract from their timestamps.

Simulation: a server’s clock (20 ppm off, wandering) disciplined over a path of three switches with a mean 5\, µ s of queueing per switch and direction, eight exchanges a second. Queueing, not the timestamps, dominates until transparent clocks remove it; the dashed line is the 100-microsecond limit. Model values; data: fig_clock.py on firm.clocksync (seeded).
Figure 4.3. Simulation: a server’s clock (20 ppm off, wandering) disciplined over a path of three switches with a mean 5 µs5\,\text{µ}\mathrm{s} of queueing per switch and direction, eight exchanges a second. Queueing, not the timestamps, dominates until transparent clocks remove it; the dashed line is the 100-microsecond limit. Model values; data: fig_clock.py on firm.clocksync (seeded).
Simulation: Allan deviation of the chapter’s oscillator left alone and of the same clock disciplined over transparent clocks. The free clock’s frequency wanders (slope +1/2); the disciplined clock’s readings jitter by nanoseconds around a correct rate (slope -1). Below a few seconds (between 2 and 8) the free oscillator is the steadier of the two; above, the servo wins by orders of magnitude. Model values; data: fig_clock.py.
Figure 4.4. Simulation: Allan deviation of the chapter’s oscillator left alone and of the same clock disciplined over transparent clocks. The free clock’s frequency wanders (slope +12+\tfrac12); the disciplined clock’s readings jitter by nanoseconds around a correct rate (slope −1-1). Below a few seconds (between 2 and 8) the free oscillator is the steadier of the two; above, the servo wins by orders of magnitude. Model values; data: fig_clock.py.
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