Precision Time Protocol

About: Precision Time Protocol is a research topic. Over the lifetime, 604 publications have been published within this topic receiving 6006 citations. The topic is also known as: PTP & IEEE 1588.

A reliable architecture based on Precision Time Protocol for WAMPAC synchronization

Abstract: Wide Area Monitoring Protection and Control (WAMPAC) systems play an increasingly important role in electric power system. They allow the measurement and the analysis of real time data to improve power system‘s reliability and efficiency. To work properly, every element of a WAMPAC system must be synchronized to a common reference time. Currently, the most common synchronization source is GPS, a system greatly vulnerable to cyber-attacks. To fully exploit WAMPAC systems‘ potential, cyber security issues must be taken into account. One possible solution could be the utilization of Precision Time Protocol (PTP) over Ethernet, as an alternative synchronization source.

Improving syntonization of synchronous ethernet nodes using multiple paths

Abstract: The joint use of clock synchronization and syntonization can provide extremely high accuracy in industrial and telecom applications. However, in typical implementations of Synchronous Ethernet , only one frequency source at a time is selected for node syntonization (even in the presence of redundant networks with multiple paths), thus losing useful information. In this paper, an algorithm able to synthesize a frequency reference from the fusion of multiple signals over different network paths is presented and validated through simulations. The results confirm that the proposed algorithm is able to improve both frequency stability and robustness of the generated reference signal.

Precision time transfer using IEEE 1588 over OTN through a commercial optical telecommunications network

Abstract: There is a need to back up critical timing infrastructure at the national level. This paper provides an update on a joint project employing commercial equipment to send national timing signals through a telecommunication network in the United States. This experiment connects the UTC(NIST) time scale located in Boulder, Colorado with the UTC(USNO) Alternate Master Clock time scale located at Schriever Air Force Base in Colorado via a telecommunication provider's optical network. Timing signals using the Precision Time Protocol (PTP) were sent in the usual two-way fashion, but each one-way delay was measured, because we had UTC time scales at both ends of the network that were within 10 ns of each other. This part of the experiment is now nearly complete. The experiment was started in April 2014 and extensions of the project will run through the end of 2016. It appears that there is at least one commercial transport mechanism that could serve to back up GPS for time transfer at the 100 ns level. We found that the asymmetry of the PTP time transfer resulted in 10's of microseconds of time transfer error, but that the stability through the entire connection was less than 100 ns, as long as the connection remained complete. This implies that if the time delays of the network could be calibrated, it could maintain under 100 ns accuracy as long as it did not go down. We have established the likely causes of the bias, as well as run simulations of various configurations in a laboratory. Thus, we have some certainty that similar results will apply if this technique were used as a service across the country. While many researchers have shown that fiber can transfer time and frequency with high accuracy, this experiment addresses the practicality of using the US telecom infrastructure for timing.

A Modular Approach for Synchronized Wireless Multimodal Multisensor Data Acquisition in Highly Dynamic Social Settings

Abstract: Existing data acquisition literature for human behavior research provides wired solutions, mainly for controlled laboratory setups. In uncontrolled free-standing conversation settings, where participants are free to walk around, these solutions are unsuitable. While wireless solutions are employed in the broadcasting industry, they can be prohibitively expensive. In this work, we propose a modular and cost-effective wireless approach for synchronized multisensor data acquisition of social human behavior. Our core idea involves a cost-accuracy trade-off by using Network Time Protocol (NTP) as a source reference for all sensors. While commonly used as a reference in ubiquitous computing, NTP is widely considered to be insufficiently accurate as a reference for video applications, where Precision Time Protocol (PTP) or Global Positioning System (GPS) based references are preferred. We argue and show, however, that the latency introduced by using NTP as a source reference is adequate for human behavior research, and the subsequent cost and modularity benefits are a desirable trade-off for applications in this domain. We also describe one instantiation of the approach deployed in a real-world experiment to demonstrate the practicality of our setup in-the-wild.

Practical Implementation of APTs on PTP Time Synchronisation Networks

Abstract: The Precision Time Protocol is essential for many time-sensitive and time-aware applications. However, it was never designed for security, and despite various approaches to harden this protocol against manipulation, it is still prone to cyber-attacks. Here Advanced Persistent Threats (APT) are of particular concern, as they may stealthily and over extended periods of time manipulate computer clocks that rely on the accurate functioning of this protocol. Simulating such attacks is difficult, as it requires firmware manipulation of network and PTP infrastructure components. Therefore, this paper proposes and demonstrates a programmable Man-in-the-Middle (pMitM) and a programmable injector (pInj) device that allow the implementation of a variety of attacks, enabling security researchers to quantify the impact of APTs on time synchronisation.