NTP Network Time Protocol (RFC 1305)

Introduction to Time in a Networked Environment

 

NTS-3000 Elproma NTP Network Time Server

 

 

 

 

NTP - Introduction to Network Time Protocol

 

 

The need for synchronized time is critical for today’s network environments. As organizations grow and the network services they provide continue to increase, the challenges involved with providing accurate time to their systems and applications also increase. Every aspect of managing, securing, planning, and debugging a network involves determining when events happen. Time is the critical element that allows an event on one network node to be mapped to a corresponding event on another. In many cases, these challenges can be overcome by the enterprise deployment of the NTP service.

 

 

 

Time in a Networked Environment

 

 

Electronic clocks in most servers and networking devices keep inaccurate time. One of several reasons for this is that designing a computer to keep accurate time is rarely a priority for computer manufacturers because it adds cost and complexity. However, even fairly accurate computer clocks are likely to vary due to manufacturing defects, changes in temperature, electric and magnetic interference, the age of the oscillator, or even computer load. Additionally, even the smallest errors in keeping time can significantly add up over a long period. Consider two clocks that are synchronized at the beginning of the year, but one consistently takes

an extra .04 milliseconds to increment itself by a second. By the end of a year, the two clocks will differ in time by more than 20 minutes. If a clock is off by just 10 parts per million, it will gain or lose almost a second a day. These measures are actually fairly optimistic examples of the accuracy of some of the clocks in modern

workstations and PCs. The types of inaccuracies that exist in computer clocks are difficult to classify. Some clock variations are random, caused by environmental or electronic variations, others are systematic, caused by a miscalibrated clock. Clearly, having any sort of meaningful time synchronization is almost impossible if clocks are allowed to run on their own. In some environments, this lack of synchronization isn’t a big issue. However, in most modern networked computing environments, time synchronization is important. To reduce confusion in shared filesystems, it is crucial for the modification times to be consistent, regardless of what machine the filesystems are on. Billing services and similar applications must know the time accurately. Some financial services even require highly accurate timekeeping by law. Sorting email and other network communications can also be difficult if time stamps are incorrect. In addition, tracking security breaches, network usage, or problems affecting a large number of components can be nearly impossible if time stamps in logs are inaccurate. Time is often the critical factor in separating cause from effect. Applications such as cyptographic key management and secure document transmission may require using accurate, encoded time stamps which match unencoded time stamps to help assure document authenticity. For instance, secure RPC needs clocks to be synced to within 15 seconds for proper operation. In addition, interactions with dynamic events such as stock market trades, aviation management, and radio and TV programming, require careful synchronization of time. As with any complex problem that is important in a wide variety of circumstances, a number of potential solutions to the time synchronization problem exist. There are several UNIX® time synchronization protocols, including Digital Time Service (alternately known as DTS or DTSS). Many other synchronization protocols and their relative merits are discussed in detail in RFC1305, which defines An Overview of NTP, the NTPv4 specification. Other time protocols have influenced the evolution of NTP, including rdate and DTS. The procedure for determining offsets evolved from a model used by telephone companies to synchronize time. NTP builds on the legacy and research efforts of these other protocols, which makes it a very robust and mature technology. NTP is a good choice for time synchronization in a variety of circumstances. Other schemes, such as DTS, are designed primarily for local area networks, while NTP is designed specifically for Internet environments. Although a number of UNIX commands provide setting or synchronizing time, they don’t have the accuracy and robust feature set present in NTP. Flexibility of the client/server relationship and security methods allow NTP to work well in almost any environment. NTP not only corrects the current time, it can keep track of consistent time variations and automatically adjust for time drift on the client. This allows for less network traffic and keeps client clocks more stable, even if the network is unavailable. In addition, the NTP daemon can automatically adjust the time at periodic increments. NTP can also operate through firewalls and has a number of security features. In addition, NTP operates on a wide variety of platforms. Simple Network Time Protocol (SNTP) is a lightweight variation of NTP which is compatable with NTP and popular on wintel machines. Since many platforms and networking devices support one or both of these protocols, NTP can be easily standardized throughout an enterprise.

 

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