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Hybrid Mode on ACX Series Routers Overview
The combined operation of Synchronous Ethernet and Precision Time Protocol (PTP) is also known as hybrid mode. The following sections explain hybrid mode in detail:
Hybrid Mode Overview
In hybrid mode, the synchronous Ethernet equipment clock (EEC) on the Modular Port Concentrator (MPC) derives the frequency from Synchronous Ethernet and the phase and time of day from PTP. Time synchronization includes both phase synchronization and frequency synchronization.
Synchronous Ethernet is a physical layer–based technology that functions regardless of the network load. Synchronous Ethernet supports hop-by-hop frequency transfer, where all interfaces on the trail must support Synchronous Ethernet. PTP (also known as IEEE 1588v2) synchronizes clocks between nodes in a network, thereby enabling the distribution of an accurate clock over a packet-switched network. This synchronization is achieved through packets that are transmitted and received in a session between a primary clock (commonly called the primary) and a client clock (also known as the client in PTP terminology). PTP synchronizes both frequency and phase including time of day. The accuracy of clock synchronization depends on factors such as packet delay variation, quality of oscillator used, network asymmetry, and so on.
Synchronous Ethernet and PTP provide frequency and phase synchronization; however, the accuracy in the order of nanoseconds is difficult to achieve through PTP or Synchronous Ethernet and they do not support a large number of network hops. Hybrid mode resolves these issues by extending the number of network hops and also provides clock synchronization accuracy in the order of tens of nanoseconds.
Hybrid mode is configured on the client. On the client, you can configure one or more interfaces as Synchronous Ethernet source interfaces.
Router clocks are categorized based on the role of the router in the network. They are broadly categorized into ordinary clocks and boundary clocks. The primary clock and the client clock are known as ordinary clocks. The boundary clock can operate as either a primary clock or a client clock.
In hybrid mode, the following show commands display
information regarding the hybrid status configuration:
The
show ptp status detailscommand displays the time and phase plane status.The
show chassis synchronization extensivecommand displays the frequency plane status.The
show ptp hybrid statuscommand displays the hybrid (combined status of frequency and phase plane) status.In hybrid mode, the
show ptp hybrid statusandshow ptp lock-statuscommands indicate the lock status asPhase Alignedin the output.
For information about configuring hybrid mode, see Configuring Hybrid Mode and ESMC Quality Level Mapping. You can use the show ptp hybrid status operational command
to find the current operating mode.
Supporting Platforms
Hybrid mode is supported on the Juniper Networks ACX Series Universal Metro Routers.
The combined operation is possible only when the PTP client and the Synchronous Ethernet source are on the same device and are traceable to the same primary reference clock (also known as PRC).
When acting as PTP slaves, the ACX Series routers can accept any external Synchronous Ethernet clock as reference and do not support building-integrated timing supply (BITS) input as frequency source in hybrid mode of operation. Only Synchronous Ethernet sources are allowed in hybrid mode. Note that when the selected Synchronous Ethernet reference fails, the router continues to work in PTP mode.
Unified in-service software upgrade (unified ISSU) is not supported when clock synchronization is configured for PTP and Synchronous Ethernet on the hybrid mode.
To switch between PTP and Synchronous Ethernet modes, you must first deactivate the configuration for the current mode and then commit the configuration. Wait for 30 seconds, configure the new mode and its related parameters, and then commit the configuration.