How to Deploy PTP Network Switches with SONiC for Nanosecond-Perfect Timing

Where financial trades, 5G networks, industrial automation, media & broadcasting, and power & utilities all hinge on nanosecond precision time synchronization, low latency is critical. However, traditional timing protocols like NTP fall dangerously short of meeting these demands. That’s why Asterfusion’s PTP network switches are designed to deliver the nanosecond-level accuracy today’s networks require. The Precision Time Protocol (PTP) is backed by hardware timestamping and Asterfusion SONiC NOS. AsterNOS’ PTP offers comprehensive configurability across standard PTP features and industry-specific profiles. This blog explores how to deploy PTP network switches with SONiC to achieve the nanosecond-level timing your business needs to stay ahead. The following are Asterfusion’s CX-M series SONiC campus switches that support PTP features.

What is PTP (Precision Time Protocol)?

Precision Time Protocol (PTP) is a protocol for clock synchronization throughout a computer network with relatively high precision and therefore potentially high accuracy. PTP is defined in the IEEE 1588 standard and is used to provide highly accurate and reliable time across local or wide area networks for various systems and applications.

Clock Node

• Time synchronization: Aligning the absolute clock time to a reference time.
• Frequency synchronization: Ensuring clocks run at the same rate, even if they start at different times.

Concepts of Clock Synchronization

• Ordinary Clock: Provides only one physical port for participating in time synchronization within a PTP domain.
• Boundary Clock: Provides two or more physical ports to participate in time synchronization in a PTP domain. One port synchronizes time with an upstream device, and the others send the time to a downstream device.
• Transparent Clock: Does not synchronize time with other devices, just forwards PTP messages between its PTP ports and measures the link delay of the messages.

For network engineers, PTP represents a paradigm shift from traditional time synchronization methods. Where NTP allows for precision within milliseconds, PTP allows for precision within nanoseconds. NTP is accurate within ten milliseconds, while PTP is accurate to within less than a microsecond, measured in nanoseconds.

How Does Precision Time Protocol (PTP) Work?

End-to-End (E2E) Delay Mechanism

This diagram demonstrates the End-to-End transparent clock mechanism, where the intermediate device (E2E TC) forwards timing messages while adding residence time corrections, and the delay measurement is performed end-to-end between the Master and Ordinary clocks.

Three main components shown:

• Master Clock (left side, depicted with a dark blue clock icon marked “L”)
• E2E TC (End-to-End Transparent Clock, middle, shown with a light blue clock icon)
• Ordinary Clock (right side, shown with a gray clock icon)

Message flow and timing:

1. SYNC message flow:
   • At time t₁, Master Clock sends SYNC message
   • Shows “Path delay (pd)” from Master to E2E TC
   • E2E TC adds “Residence Time(rt)”
   • Shows “Path delay (pd)” from E2E TC to Ordinary Clock
   • Message arrives at Ordinary Clock at time t₂
2. FollowUp message:
   • Shown as dashed line from Master Clock through E2E TC to Ordinary Clock
   • Contains timing information for the SYNC message
3. Delay Request/Response mechanism:
   • Delay_Req(t₃) sent from Ordinary Clock at time t₃
   • Delay_Req(t₃) forwarded through E2E TC
   • Arrives at Master Clock at time t₄
   • Delay_Resp(t₄) sent back from Master Clock
   • Delay_Resp(t₄) forwarded through E2E TC to Ordinary Clock

Calculations shown on the right:

• t₂ – t₁ = offset + delay
• t₄ – t₃ = delay – offset
• delay = (t₂-t₁)+(t₄-t₃)/2
• offset = (t₂-t₁)-(t₄-t₃)/2
• T_OC_new = T_Master ± offset

Peer-to-Peer (P2P) Delay Mechanism

This diagram demonstrates how PTP achieves precise time synchronization across network devices by measuring and compensating for network delays and residence times in transparent clocks.

Three main components shown:

• Master Clock (left side, depicted with a dark blue clock icon marked “L”)
• P2P TC (Peer-to-Peer Transparent Clock, middle, shown with a light blue clock icon)
• Ordinary Clock (right side, shown with a gray clock icon)

Message flow and timing:

1. At time t₁, the Master Clock sends a SYNC message
2. This message includes “Residence Time(rt)” and reaches the P2P TC at pt₁
3. A “correctionField” is shown in yellow/orange between the P2P TC and Ordinary Clock
4. The SYNC message reaches the Ordinary Clock at time t₂

Delay measurement process:

• pDelay_Request messages are sent from pt₂ to pt₃
• pDelay_Response messages are sent back from pt₄ to pt₁

Calculations shown:

• PD1 = (pt₂-pt₁)+(pt₃-pt₂)/2
• PD2 = (pt₄-pt₁)+(pt₄-pt₃)/2

Final synchronization formulas:

• correctionField = PD1 + rt
• offset = t₂ – t₁ – correctionField – PD2
• T_OC_new = T_Master ± offset

The Core Distinctions Between E2E and P2P

✓AsterNOS supports operating in both E2E and P2P modes, and can be used with various PTP profiles.

SONiC-Based PTP Network Switch Deployment Across Industries

Broadcast and Media Industry

The diagram illustrates a broadcast and media network topology. It shows how PTP network switch enables precise synchronization across various media types (audio, video, metadata) in broadcast environments, utilizing multiple domains and redundant timing sources.

Why: PTP provides the broadcast and media industries with highly accurate time synchronization, ensuring less than 20ns accuracy, which ensures seamless alignment of audio, video, and metadata traffic.

How: Supports Best Master Clock Algorithm (BMCA) for optimal grandmaster selection, enabling fast switchover to backup clock upon primary clock failure. Supports multiple PTP domains, with separate domain numbers assigned for audio and video to avoid conflicts.

5G and O-RAN Networks

The diagram shows an O-RAN Fronthaul Transport network topology. The diagram shows PTP timing signals flowing from GNSS through the DU to coordinate timing across the entire O-RAN fronthaul network, ensuring precise synchronization for 5G radio operations including CoMP coordination and TDD scheduling.

Why 5G and O-RAN Networks Need PTP?

1. Multiple RUs coordinate through CoMP to achieve signal combining and performance enhancement, which requires precise time synchronization between the RUs.

2. In a TDD network, the uplink and downlink share the same frequency, so PTP time synchronization is required to schedule signal transmission and avoid interference precisely.

Grandmaster + Carrier Ethernet Switch + O-DU

• Support IEEE1588v2 and SyncE protocols, GNSS receiver, 1PPS, ToD, 10MHz timing interfaces.
• 2 optional DPU, it is also possible to migrate applications from standard x86 servers to ARM-based DPU, which minimizes O-DU into a single box.
• Enterprise SONiC with comprehensive layer2, layer3, virtualization, security, and management features, suitable for mobile fronthaul, backhaul, and O-RAN networks.

PTP Network Switches’ AsterNOS PTP Main Features

AsterNOS PTP Delivers Enterprise-Grade Synchronization

Complete Protocol Flexibility and Compatibility
AsterNOS PTP offers unmatched versatility by supporting all essential PTP clock roles: Grandmaster Clock (GC), Boundary Clock (BC), Transparent Clock (TC), and Ordinary Clock (OC) – ensuring seamless integration with any network topology. The system offers the maximum level of flexibility in deployment with its timestamping capabilities (One-step and Two-step) and comprehensive delay measurement capabilities (End-to-End as well as Peer-to-Peer) that allow businesses to improve performance based on the specific needs for their network accuracy requirements.

Multi-Profile and Multi-Instance PTP

• Compliant with mainstream PTP profiles including IEEE 1588v2, ITU-T G.8275.1, and SMPTE ST2059-2.
• Supports concurrent multi-instance PTP operation to prevent domain conflicts, ideal for broadcast, 5G, and industrial applications.

Integrated Converged Platform Design

• Built-in GNSS interface, 1PPS, 10MHz, and ToD support.
• High-performance DPU enables full integration of O-DU and PTP functions.
• Synchronization + forwarding in a single unit.

High Precision Large Scale Time and Frequency Synchronization

• Synchronization accuracy within ±20 nanoseconds, suitable for ultra-precise applications such as video broadcasting, phasor measurement, and mobile RAN.
• Each device supports up to 48 concurrent slave clocks, enabling cost-effective deployment in large-scale cluster scenarios.

Conclusion

Implementing PTP network switches equipped with SONiC to ensure nanosecond-perfect timing has become an essential requirement across all industries that require precision timing synchronization. In this article we’ve examined the key components of a an effective PTP implementation, from comprehending the physical requirements to achieve accurate timestamping to configuring the SONiC’s programmable PTP profiles to meet specific applications in the industry for example, broadcast media that requires sub-20 nanosecond precision to ensure seamless audio-video synchronization and 5G O-RAN networks require coordinated timing between distributed radio units. A deep technical dive into the delay mechanisms and clock hierarchy design support has revealed the flexibility of SONiC’s open architecture, which allows the flexibility required to satisfy various timing requirements while avoiding vendor lock-in.

Refer to:

What is NTP and PTP?
What is PTP and How Does It Work?
Linux PTP or PTP-optimized SONiC – Which One to Choose for Network Synchronization?