Televes OLT 769401, User Manual

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Descripción del producto
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Figure 2-18: Delay from Slave-Clock Device to Master-Clock Device
OLT equipment configured as Boundary Clock (BC)
The OLT configured as BC recover the clock and regenerate the PTP packets r eceives timing through the TU40G unit.
The OLT is effectively a node that recovers timing from the incoming 1588v2 (as a Slave) and then uses this recovered timing to re-time the
outgoing signal. It then acts as the 1588v2 Master for the next node. By using this mechanism, the impact of PDV is minimized as the packets will
not travel through many routers or switches between Master and Slave (which would have caused PDV).
The OLT configured as Boundary clock can be considered as performing both the slave and master function. The 1588v2 message flow is terminated
and the frequency and/or time recovered from the ingress messages. This is used to guide its internal reference. The boundary clock then acts
as the master to the downstream clock by generating a new 1588v2 message flow using timestamps generated from its internal reference . The
downstream flow to the ONT through the GPON LC (TG16G) unit, Figure 2-.
Figure 2-19: Boundary Clock Synchronization mechanism (Mobile Backhaul Example)
Measurements & Limits
The measurement limits for Frequency Accuracy (MTIE/TDEV) are specified by the relevant ITU-T standards that specify clock accuracy, for example
G.813, G.823, G.824. G.8261, or “Timing and Synchronization Aspects in Packet Networks”, specifies the upper limits of allowable network jitter and
wander, the minimum requirements that network equipment at the TDM interfaces at the boundary of these packet networks can tolerate, and
the minimum requirements for the synchronization function of network equipment. G.8263 “Timing characteristics of packet-based equipment
clocks” specifies the outlines requirements for timing devices used in synchronizing network equipment that operates in the interworking function
(IWF) and other network elements as defined in Recommendation ITU-T G.8261/Y.1361.