Guidelines to Configure Hybrid Mode on ACX Series Routers

Read this topic to understand the guidelines to configure hybrid mode on ACX routers.

Guidelines to configure hybrid mode on ACX Series Routers are provided below:

• 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 the PTP Mode feature 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 TimeTransmitter Clock Algoritm (BTCA).

  • 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).