What is Precision Time Protocol (PTP)?
Precision Time Protocol (PTP) services provide the most accurate and secure time available to IP-based networks. With time traceable to UTC at the level of nanoseconds (billionths of a second), PTP is far more accurate than, for example, Network Time Protocol (NTP). PTP also avoids the security, stability and logistical issues that cause significant problems when using GNSS services.
What is PTP?
PTP is a high-precision protocol for delivering time and frequency over IP-based networks. It has been designed for systems needing the highest level of accuracy. By enabling hardware time-stamping, and used in conjunction with specific hardware arrangements, PTP can enable time stamping to the level of tens of nanoseconds.
The most accurate time-based protocol available for networks, PTP, was originally defined in the IEEE 1588-2002 standard ("Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems"). It offers the highest level of time precision and security without the inherent weakness of services that rely on GNSS.
How do PTP services work?
PTP enables highly-accurate time synchronisation of clocks in IP based networks by sending packets between leader and follower clocks. The reference clock (also called a grandmaster) may be controlled by an atomic clock (such as the caesium clocks used by Netnod in its PTP time service). Atomic clocks are the most accurate source of time currently in use. In fact, it is the weighted average of the time kept by around 500 atomic clocks in 70+ laboratories worldwide that generates UTC.
What are the benefits of PTP?
PTP services are delivered over dedicated fibre optic connections. This is far more secure than GNSS services, which are delivered over radio signals susceptible to all manner of natural and human interference. As PTP uses dedicated fibre connections, precise adjustments can be made for the time it takes packets to travel between the primary and client clocks. With the correct calibration of equipment, it is possible to cancel any networking delay. This means that PTP services avoid the inaccuracies in time propagation that happens with NTP over the public internet and GNSS. This gives customers a guaranteed, stable level of high-precision time. It also means that PTP enables highly-accurate time stamps traceable to UTC to the level of nanoseconds.
PTP and time stamping
Time stamps play a crucial role in everything from financial transactions, to transport logistics and computer forensics. They enable systems to track the exact order of events but they require accurate, reliable and secure time if they are to be effective. Time stamps also need to be traceable to UTC to fulfil regulatory requirements, such as the MIFID II regulation for the financial industry. For certain financial transactions, such as High-Frequency trading, the regulation specifies time stamping traceable to UTC at the level of microseconds (millionths of a second). By enabling hardware time-stamping, and used in conjunction with specific hardware arrangements, PTP can provide time stamping to the level of nanoseconds (billionths of a second).
PTP and traceable time
Traceable time means that the time stamping of a specific event can be traced all the way back through the relevant systems and networks to UTC. Each part of the traceability chain must be precisely measured, monitored and archived for future reference. This requires an extremely high-level of expertise, for example: high-precision calibration, continuous monitoring of all timing equipment and documentation of the the setup and methods of your timestamping infrastructure allowing full traceability through ever step of the process.
The requirements of traceable time put a significant burden on networks. The results of not providing traceable time can result in non-compliance with EU regulations and heavy financial penalties. It is usually much easier, safer and cost-effective for networks to get PTP services from a trusted time provider. This ensures the time they use is accurate, secure and traceable as well as guaranteeing you they can fulfil regulatory requirements. With all the complexity and costs involved, it is better to outsource this service from the the experts and focus on running your network.
What is the difference between PTP and NTP?
The main difference between PTP and NTP is that PTP is used with hardware support in the equipment for high resolution and accuracy, and with controlled network connections. This prevents situations such as routing asymmetries that are normal for data traffic but result in time errors. NTP is often used over connections meant for other data traffic and these connections are not optimised for time accuracy.
When considering whether to use NTP or PTP, you need to evaluate your accuracy, reporting and regulatory requirements.
If you don’t need highly accurate time, NTP can be a good choice for your network. Netnod provides a free NTP service available to anyone. For a good introduction to NTP, you can read our NTP best practice guide. In the past, NTP has been vulnerable to a range of security issues. Netnod has helped develop the Network Time Security (NTS) standard that makes NTP more secure.
What is the difference between PTP and GNSS?
The Global Navigation Satellite System (GNSS) has been in operation since the late 1970s. GNSS services, which include GPS, GLONASS, Galileo, and BDS, use a constellation of satellites with high accuracy atomic clocks. These transmit radio signals to GNSS receivers on earth enabling them to determine position and time to a high level of accuracy.
These services can have a range of issues that can introduce significant errors in time and frequency measurements. For mission-critical systems, these errors can be disastrous and include:
- signal interference
- rollover issues
- vulnerability to attack using signal jamming and spoofing
In recent years, GNSS has become increasingly vulnerable due to the wide availability of technology for compromising radio-based services. As a result, it is now much easier for malicious actors to prevent GNSS data from getting through (jamming) or to trick a GNSS receiver into believing fake data (spoofing).
Who uses PTP?
As a time distribution protocol offering the highest level of precision and security, PTP is used in military applications, the energy industry, at high-level research institutes (such as CERN), in telecommunications and in the financial services industry. PTP is the only protocol that can deliver the necessary level of time-stamping and traceability required by the MIFID II regulations for financial transactions. It also offers a more robust solution than GNSS for customers operating mission-critical services.
Netnod’s PTP service
Netnod’s PTP service is delivered over a dedicated fibre and offers a robust, reliable and highly accurate source for traceable time and frequency. If you are working in a sector where every nanosecond counts, you can trust Netnod to keep you on time.