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PTP & SyncE: Sub-100ns Timing for 5G and AI Fabrics

5G NR, time-sensitive AI workloads, and modern industrial transport all demand sub-microsecond phase alignment across the network. OcNOS implements IEEE 1588v2 PTP (Class C/D), ITU-T SyncE, and the hybrid mode that combines them, with boundary and transparent clocks distributed across validated cell-site routers.

Timing Distribution: Grandmaster to Cell Site

A GPS-disciplined grandmaster injects time at the aggregation site. Each hop is a PTP boundary clock (BC) running OcNOS, recovering frequency from SyncE and phase from PTP, and re-stamping events down to the cell-site router.

PTP timing topology: GPS-fed grandmaster distributing Class C and D timing through boundary clocks to cell-site routers and a 5G gNB
PTP: GPS grandmaster, boundary clocks, and cell-site routers feeding a 5G gNB.

Why timing matters more than ever

5G TDD slot alignment, coordinated multipoint (CoMP), and emerging time-sensitive networking (TSN) profiles all require phase accuracy below 1.5 µs end-to-end, and most modern radio profiles tighten that to a few hundred nanoseconds. AI fabrics increasingly want sub-microsecond timestamps for tracing GPU collective stalls. OcNOS combines IEEE 1588v2 PTP for phase with SyncE for frequency in a single hybrid clock per hop, keeping every interface in lock with the grandmaster.

The OcNOS PTP & SyncE implementation

Profiles

G.8275.1 / G.8275.2

Full-on-path (G.8275.1) and partial-timing-support (G.8275.2) profiles, plus default and telecom-2008 profiles for legacy interop.

SyncE

G.8261 + G.8262

SyncE frequency distribution with EEC-Option 1/2 clock specs, ESMC quality-level signalling, and best-source selection.

Boundary Clock

Class C / Class D

Boundary and transparent clock modes with hardware time-stamping; validated platforms achieve Class C and Class D per-hop specs.

Holdover

Reference loss tolerance

OCXO and rubidium-disciplined holdover keeps phase within budget for hours when the reference path goes away, critical for cell-site survival.

Telemetry

gNMI sync state

Per-port PTP servo state, offset-from-master, mean-path-delay, and SyncE QL exposed as streaming sensors for proactive timing alarms.

Validated Platforms

Cell-site routers

Validated PTP/SyncE on UfiSpace S9500-22XST and S9510-28DC class hardware, including 1PPS / 10MHz / ToD external timing ports.

What you get with OcNOS timing

  • Single image, full timing stack. PTP and SyncE are part of the OcNOS-SP CSR image, with no separate timing license tier.
  • Open hardware certified. Validated end-to-end on cell-site routers with hardware time-stamping ASICs and disciplined oscillators.
  • Mature alarms. Phase-out-of-bounds, holdover-entered, and QL-degraded events surface via syslog, gNMI, and SNMP traps.
  • 5G-ready. Reference designs for fronthaul (xHaul) and midhaul deployments aligned to ITU G.8275.1 budget tables.
5G Backhaul RoCEv2 OcNOS-SP CSR

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FAQ

Frequently asked questions

What is the difference between PTP and SyncE?
PTP (IEEE 1588v2) delivers phase and time-of-day accuracy, while SyncE (ITU-T G.8261/G.8262) delivers physical-layer frequency. OcNOS runs both together as a hybrid clock per hop, recovering frequency from SyncE and phase from PTP.
Which PTP profiles does OcNOS support?
OcNOS supports the G.8275.1 full-timing-support and G.8275.2 partial-timing-support telecom profiles, plus default and telecom-2008 profiles for legacy interoperability.
What timing accuracy can OcNOS achieve?
OcNOS supports boundary and transparent clock modes with hardware time-stamping, and supported platforms meet IEEE 1588v2 Class C and Class D per-hop specs, targeting a phase budget below 100ns for 5G transport.
What happens to timing if the reference is lost?
OCXO and rubidium-disciplined holdover keeps phase within budget for hours when the reference path goes away, which is critical for cell-site survival. Phase-out-of-bounds and holdover-entered events surface via syslog, gNMI, and SNMP traps.
Which platforms support PTP and SyncE in OcNOS?
PTP and SyncE are tested on cell-site routers such as UfiSpace S9500-22XST and S9510-28DC class hardware, including 1PPS, 10MHz, and ToD external timing ports, and ship in the OcNOS-SP CSR image with no separate timing license tier.
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