Usage Analysis of the NIST Internet Time Service

Abstract

The Internet Time Service (ITS) at the National Institute of Standards and Technology (NIST) currently receives over 16 billion time requests per day. ITS servers derive their system time from the NIST atomic-referenced time scale and distribute it freely to the public. Here we explore ITS usage patterns discovered by analysis of inbound network traffic. For example, over a period of four weeks, just two of the ≈ 20 ITS servers received requests from 316 million unique Internet Protocol (IPv4) addresses, which is at least 8.5 % of the entire Internet. We offer recommendations for networked device/software manufacturers, and providers and consumers of network time services. OverviewAmong national metrological institutes, NIST operates the largest ensemble of time-serving computers (timesevers) on the public Internet [1]. The approximately twenty [2] servers' system clocks are synchronized to a time scale governed by atomic clocks and primary frequency standards [3], the laboratory's realization of Coordinated Universal Time, UTC(NIST). The timeservers are geographically diverse, operate with independent synchronization links, and provide a source of time independent of Global Navigation Satellite Systems such as the Global Positioning System (GPS) [4]. Historically, traffic to the ITS has grown exponentially and now (at time of writing) exceeds 1.6 × 10 10 requests daily (see Fig. 1). Applications and demand for accurate network time transfer include securities trading [5], distributed databases [6], and realtime cyber-physical systems [7][8][9]. Generally, while information security applications do not yet require UTC at high resolution, they do rely on time accuracy and network integrity [10]. For these reasons, trusted, highly available primary sources of network time like the ITS are vital public resources. Industry forecasts predict even more classes of appliances will become networked (i.e., Internet of Things [11]), implying further significant growth potential in demand for network time. Therefore, it is important to understand ITS usage patterns in order to optimally use and provision ITS resources.Since background information about network time transfer and the ITS [12] is available elsewhere, we cover only relevant details in Sec. 2. Thus far, the only published ITS usage statistics are daily request totals. In this work, we explore usage patterns in finer detail. In Sec. 3 we present new findings including temporal patterns in request rate, and estimates of the number, character, and behavior of unique clients. Given the large request rate (averaging over 28,000/s on one server), and the delay-sensitive nature of the

Accurate, Traceable, and Verifiable Time Synchronization for World Financial Markets

“…The requirement was originally enforced only for the NASDAQ stock market, but the NYSE, through Rule 132A [15], adopted requirements identical to NASD Rule 6953 in 2003. Figure 1 shows an OATS compliant clock, still available at this writing, that can obtain NIST time from either radio station WWVB at 60 kHz [16] or from the NIST Internet Time Service (ITS) [17].…”

“…Because UTC(NIST) is a close real-time approximation of UTC, it can also be utilized as an official time source for financial exchanges throughout the world. NIST distributes UTC(NIST) to the general public through a variety of services that operate over various mediums including WWV, WWVH, and WWVB, which broadcast time signals via high frequency (HF) and low frequency (LF) radio signals [16,32]; by the Automated Computer Time Service (ACTS), which broadcasts time codes via ordinary telephone lines [33]; and by the Internet Time Service (ITS), which broadcasts billions (10 9 ) of time codes per day via the public Internet [17]. However, due to uncompensated propagation delays, each of these services delivers time to the user that is far less accurate than the time kept at NIST.…”

Metrological and Legal Traceability of Time Signals

“…The primary purpose of NTP is the synchronization of computer clocks and network appliances. The demand for these services is so high that many billions of NTP synchronization requests are currently received every day [14]. At this writing (November 2017) the average number of NTP requests received per second is about 460 000 at NIST and about 15 000 at the USNO.…”

Impact of Quality of Service on Cloud Based Industrial IoT Applications with OPC UA

“…The NTP (Network Transfer Protocol) has been used to synchronize each system with a local time server locked to GPS clock. The synchronization uncertainty using NTP may vary with the quality of the network connection in terms of latency [22,23] but all the considered systems are connected via a local area network with time server, reducing the variability to the minimum. Nevertheless, the synchronization uncertainty of the devices involved in this use case is estimated in different ways.…”

“…Nevertheless, the synchronization uncertainty of the devices involved in this use case is estimated in different ways. For the IIoT Gateway, the time synchronization is experimentally measured considering the residual time offset after compensation, as listed in the NTP statistics [23]. For the Machine, the equivalent synchronization uncertainty is derived from Siemens documentation that sets the maximum error to 0.2 ms and by supposing the error distribution is uniform.…”