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Guidelines to Configure Hybrid Mode

Keep the following points in mind while configuring hybrid mode on ACX Series routers:

  • In a Hybrid Operation, the Frequency Module derives frequency from the Synchronous Ethernet or BITS (T1/E1) clock or 10 MHz clock and Phase from the IEEE-1588v2 (PTPv2). The current deployments are all LTE-TDD based and require a phase accuracy of only 1.5us and it is expected that this performance can be achieved without requiring frequency assist.

  • Frequency Plane (Synchronous Ethernet, BITS (T1/E1), 10 MHz) is not impacted by the phase or time plane. The frequency plane derives the frequency from Synchronous Ethernet, BITS (T1/E1) and 10 MHz.

  • Phase/Time Plane uses the Frequency which is derived locally from the equipment (Synchronous Ethernet, BITS (T1/E1), 10 MHz). To achieve phase accuracy of less than 1.5us, both Frequency Input source and PTP sources traceable to a primary reference source (PRS) or primary reference clock (PRC). Hybrid mode is supported in a ring topology.

  • You can configure the following frequency sources for hybrid node:

    • Synchronous Ethernet 1G, 10G with/without ESMC

    • BITS T1 Clock

    • BITS E1 Clock

    • 10 MHz Clock

    • T1 Interface

    • E1 Interface

  • You can configure the following phase sources for hybrid node:

    • PTP IPv4 with or without unicast negotiation

    • PTPoE with or without stateful port

  • By enabling the hybrid mode, the convergence time period is reduced and locking happens quickly.

  • You can configure the PTP Source as phase or time source for hybrid mode.

  • You can configure Layer 2 rings for PTPoE with stateful ports and Synchronous Ethernet with ESMC for Layer 2 ring topologies.

  • When you enable hybrid mode, each node generates a phase error of or plus or minus 100 nanoseconds (without Phy Timestamping) or plus or minus 50 nanoseconds with Phy timestamping feature. This phenomenon requires Frequency (SyncE/BITS/10 MHz) source and PTP source must be traceable to same PRC/PRS source.

  • Fully redundant and resilient ring based configurations of up to 10 nodes are supported, targeting the 1 microsecond phase requirement for a form of 4G known as Long-Term Evolution-Time Division Duplex (LTE-TDD). A single node or link failure is accommodated and all nodes are able to maintain phase accuracy to be +/- 1us accurate to a common source.

  • Hybrid mode for PTP IPv4 rings is not supported.

  • Dynamic switchover from Hybrid to PTP mode is not supported in ACX routers.

  • BITS T1 Clock with SSM is not supported. BITS E1 Clock with SSM is not supported.

  • Hybrid Mode: Time Of Day (TOD) as Phase and Frequency as SyncE/BITS/10 MHz is not supported. Simultaneous PTP IPv4 Ring and SyncE Hybrid Mode are not supported.

  • Hybrid Mode with Phy Timestamping feature is not supported only on ACX500 series routers.

  • Dynamic Switchover from Hybrid to PTP Mode feature is not supported.

  • Hybrid Feature on aggregated Ethernet (ae-) interfaces is not supported.

  • When you configure hybrid mode, the following processes take place.

    • The best of the configured PTP time sources is selected by the PTP Best Primary Clock Algoritm (BMCA).

    • The best of configured chassis synchronization sources is selected by the synchronization source selection algorithm.

    • During the boot-up process, if valid sources are configured at the [edit chassis synchronization] hierarchy level and chassis synchronization mode in free-running mode, valid PTP source available case, system continues to operate in hybrid mode ( In this case, chassis synchronization is in free-run mode, whereas PTP is in locked mode). When both primary and secondary frequency sources fail, system still works under hybrid mode ( In this case, chassis synchronization is in hybrid mode and PTP is in locked mode).