7210 SAS-MXP, R6, R12, S, SX, T BASIC SYSTEM
CONFIGURATION GUIDE RELEASE 22.9.R1
System management
Network synchronization is commonly distributed in a hierarchical PTP topology at the physical layer, as
shown in the following figure.
Figure 21: Conventional network timing architecture (North American nomenclature)
The architecture shown in the preceding figure provides the following benefits:
• It limits the need for high quality clocks at each network element and only requires that they reliably
replicate input to remain traceable to its reference.
• It uses reliable physical media to provide transport of the timing signal. It does not consume any
bandwidth and requires limited additional processing.
The synchronization network is designed so a clock always receives timing from a clock of equal or higher
stratum or quality level. This ensures that if an upstream clock has a fault condition (for example, loses its
reference and enters a holdover or free-run state) and begins to drift in frequency, the downstream clock
will be able to follow it. For greater reliability and robustness, most offices and nodes have at least two
synchronization references that can be selected in priority order (such as primary and secondary).
Further levels of resiliency can be provided by designing a capability in the node clock that will operate
within prescribed network performance specifications without any reference for a specified timeframe. A
clock operating in this mode is said to hold the last known state over (or holdover) until the reference lock
is once again achieved. Each level in the timing hierarchy is associated with minimum levels of network
performance.
Each synchronization capable port can be independently configured to transmit data using the node
reference timing. In addition, some TDM channels can use adaptive timing or loop timing.
Transmission of a reference clock through a chain of Ethernet equipment requires that all equipment
supports Synchronous Ethernet. A single piece of equipment that is not capable of performing
3HE 18197 AAAB TQZZA
© 2022 Nokia.
Use subject to Terms available at: www.nokia.com/terms/.
257
SPACER TEXT
To Next Page
Loading...