Network Time Protocol

Business - Information Systems: Network Time Protocol

Network Time Protocol: The Best Alternative Today?

Time is money, of course, but it is also the accepted framework in which the modern world operates. For most civic functions, though, publicly available time is regarded as entirely adequate and many people consider being a few minutes early or late completely acceptable. For computers, though, a few minutes (or even a few seconds) one way or the other can spell the difference between a successful application and a failed one. Clearly, for these high-technology applications, more sophisticated and reliable methods are required to ensure smooth functioning. For this purpose, many computers use the so-called "Network Time Protocol" (NTP), which is an Internet standard protocol (built on top of TCP/IP) that assures accurate synchronization to the millisecond of computer clock times in a network of computers. This paper provides an overview of Network Time Protocol, following by a general discussion concerning its current applications and potential future trends. A summary of the research and important findings are provided in the conclusion.

Review and Discussion

Background and Overview. Running as a continuous background client program on a computer, NTP sends periodic time requests to servers, obtaining server time stamps and then using them to adjust the client's clock. According to the organizers of the Network Time Protocol project (2007), "NTP is a protocol designed to synchronize the clocks of computers over a network. NTP version 3 is an internet draft standard, formalized in RFC 1305. NTP version 4 is a significant revision of the NTP standard, and is the current development version, but has not been formalized" (NTP Project 2). The current Network Time Protocol (Version 3) has been in use since 1992 and has been characterized by nominal accuracy in the low milliseconds; however, modern workstations and networks are much faster today, with attainable accuracy in the low microseconds (Mills 9). The NTP Version 4 architecture, protocol and algorithms have been evolved to achieve this degree of accuracy:

Improved clock models which accurately predict the time and frequency adjustment for each synchronization source and network path.

Engineered algorithms reduce the impact of network jitter and oscillator wander while speeding up initial convergence.

Redesigned clock discipline algorithm operates in frequency-lock, phase-lock and hybrid modes (Mills 9).

These improvements, confirmed by empirical study, have been found to improve accuracy by about a factor of ten, while allowing operation at much longer poll intervals without significant reduction in accuracy (Mills 9). Some of the current uses for NTP include synchronization of client workstation clocks to the U.S. Naval Observatory Master Clocks in Washington, D.C. And Colorado Springs, Colorado (Mills 3). The architecture of a typical NTP process is shown in the schematic in Figure 1 below:

Figure 1. NTP Architecture.

Source: Mills 6.

According to Mills (2007) of the Network Time Protocol Project, Network Time Protocol is used to synchronize the clocks of hosts and routers in the Internet and the following represent some salient features of NTP today:

The National Institute of Standards and Technology (NIST) estimates that 10-20 million NTP servers and clients deployed in the Internet and its tributaries all over the world and every Windows/XP has an NTP client;

NTP provides nominal accuracies of low tens of milliseconds on WANs, submilliseconds on LANs, and submicroseconds using a precision time source such as a cesium oscillator or GPS receiver;

NTP software has been ported to almost every workstation and server platform available today - from PCs to Crays - Unix, Windows, VMS and embedded systems, even home routers and battery backup systems; and,

The NTP architecture, protocol and algorithms have been evolved over the last two decades to the latest NTP Version 4 software distributions.

Furthermore, Mills maintains that NTP can reasonably be said to be the longest running, continuously operating, ubiquitously available protocol in the Internet; the NIST, as well as their counterparts in other countries, currently provide multiple NTP primary servers directly synchronized to national standard cesium clock ensembles and GPS. More than 230 Internet primary servers are already in Australia, Canada, Chile, France, Germany, Israel, Italy, Holland, Japan, Norway, Sweden, Switzerland, UK, and the United States and NTP provides function to more than a million Internet servers and clients are all over the world (Mills 4). Network Time Protocol is used by agencies and organizations such as the U.S. Weather Service, U.S. Treasury Service, the Internal Revenue Service, Public Broadcasting Station, Merrill Lynch, Citicorp, GTE, Sun, DEC, Hewlett-Packard and others etc. Moreover, private networks are reported to have more than 10,000 NTP servers and clients behind firewalls; one (GTE) reports in the order of 30,000 NTP workstations and PCs and NTP has even been used on the NASA Shuttle and in the Antarctica in planning efforts for the envisioned Mars Internet (Mills 5).

Future Trends. While NTP provides enormously reliable time synchronization for computers, some computer vendors are opting for different approaches that provide superior results for their systems. For example, Compuware employs its own time server wherein all time is calculated relative to the central-site "Probe Manager"; by contrast, Agilent and Viola use the Network Time Protocol and a round-trip message's response time, divided by half, is assumed to represent the one-way latency (Hommer, Mier and Molle 40). According to Hommer and his colleagues (2002), "This is not nearly as reliable as the global positioning system timing, since it presumes that both paths of the round trip exhibit symmetrical latency behavior" (Hommer et al. 40). This point is also made in their essay, "Measuring SLA Compliance," wherein Mier and Percy (2001) report that, "One of the most advanced features that some network-monitoring products support today is time synchronization between remote sites using the satellite-based Global Positioning System, or OPS. This can yield extremely accurate temporal measurements, such as latency and jitter" (34). These authors add that latency represents the end-to-end, one-way delay that occurs between two remote locations; while this aspect of network monitoring is extremely important to applications such as Voice over Internet Protocol, it is not as important to data-retrieval transactions such as Web page requests (Mier and Percy 34). By contrast, "jitter" refers to the variation in latency that takes place over time; like latency, jitter is an important measure to real-time traffic such as VoIP, but it is of virtually no consequence to non-real-time data (Mier and Percy 34). In this regard, Mills advises that, "Engineered algorithms reduce jitter, mitigate multiple sources and avoid improperly operating servers. The system clock is disciplined in time and frequency using an adaptive algorithm responsive to network time jitter and clock oscillator frequency wander" (5). According to Mills (2007), the following types of applications stand to benefit the most from the precision offered by NTP:

Distributed database transaction journaling and logging

Stock market buy and sell orders

Secure document timestamps (with cryptographic certification)

Aviation traffic control and position reporting

Radio and TV programming launch and monitoring

Intruder detection, location and reporting

Multimedia synchronization for real-time teleconferencing

Interactive simulation event synchronization and ordering

Network monitoring, measurement and control

Early detection of failing network infrastructure devices and air conditioning equipment