Accurate, reliable and secure time has become essential to many types of systems, applications, and key services considered part of today’s enterprise networks.  Here’s a primer on using NTP for Time Synchronization, and best practices for keeping time accurate, reliable and secure.

The importance of synchronizing clocks throughout a global network cannot be understated. As technology rapidly improves and businesses continue to expand throughout the globe, more and more companies need to fully embrace some of these innovative time synchronization processes.

Why do you need your own time server although there are time servers available on the internet?

In principle it is possible to synchronize your computers with time servers on the internet. However, a lot of our customers rely on their own time server in their network environment for security and/or maintainability reasons.

• Particularly in the case Time Server you or a responsible person can be notified by mail or SNMPtrap if there is a malfunction in your time synchronization.
• The clients on the network do not depend on an active internet connection.
• The clients on the network do not depend on the availability of an external time server
• A test of other freely available time servers (not PTB!) reported that many NTPservers distributed a significantly wrong time, although they were classified as stratum-1 time servers. This is the responsibility of the server’s administrators.
• If an internet connection is working properly then NTP can determine and account for the packet transmission delays quite reliable. However, if the internet connection is at its capacity limit, time synchronization can be significantly degraded due to high dispersion in packet transmission delays. Reasons for this may be hacker attacks, which must not address your own network, or new viruses causing a huge flood of emails, like it has already happened in the past.
• An own time server cannot easily be compromised out of the internet. At the first moment this sounds trivially, however, there has been a case which really occurred and which caused some concern to the NTP community:
  A manufacturer of low-cost routers had the IP address of a public NTP server hard coded into the firmware in order to let the routers get their time from that server. Additionally, the implementation of the firmware was faulty, which resulted in a huge flood of NTP queries being sent to the NTP server. This did not even constrain the function of the NTP server, but also caused large costs to the operator due to the huge network traffic. In this case not even the deactivation of the NTP server did help

Who Needs Time Synchronization?

Air Traffic Control, Power Substations, Satellite communication, Banks, Cash Terminals, Stock Exchange, Data Centers, Traffic Management, Wind Energy Plants, Observatories Research Vessels , Oil Production, Audio & Video Broadcasting ….many more.

Network Time Synchronization Protocols

• Network Time Protocol (NTP)
• Invented later in the 1980s, 0.2 ns resolution → supports high accuracy
• Current protocol version is v4, compatible with older versions
• Standard protocol for time synchronization in Unix/Linux/*BSD, and Windows
• Reference implementation available as free software

Precision Time Protocol (PTP/IEEE1588)

• v1 from 2002, v2 from 2008, v2 is not compatible with v1
• Nanosecond resolution, eventually yields some nanoseconds accuracy under specific conditions (e.g. hardware times tamping on every network node)
• Open source implementations available

New “White Rabbit” Project

• Sub-nanosecond accuracy over Ethernet
• PTP over Synchronous Ethernet (SyncE)
• Both hardware and software available as Open Source

 How to get the accurate time into the system/application?

• Where do I get the time from? At which accuracy and precision?
• Long wave radio clock (DCF77, WWVB, MSF, JJY, …)
• Telephone services (ACTS by NIST, PTB)
• GNSS satellite receiver (GPS, GLONASS, Galileo, Beidou, …)
• Time server / network protocols (NTP, PTP, “White Rabbit”)

Which ways to get the time?

• PCI card/USB: Can always read the current time immediately
• Serial/USB: Wait for time string. When sent? Transmission delay? ➔ Similar to strokes of a church bell
• Hardware Pulses: Acquire system timestamp when on-time slope detected. ➔ How is slope detected? Latencies?
• Network / ACTS: Send query, wait for reply, try to determine packet delays

Time Distribution

• GPS controlled NTP/PTP time server
• Provides clients with very accurate time
• Single antenna cable required
• NTP with good accuracy for “normal” servers
• PTP with highest accuracy for special requirements
• PTP PCI cards get high accuracy into a server
• PTP-aware switches required for high accuracy
• Standard patch cables instead of special antenna cables
• Optionally additional hardware output signals (1 PPS, IRIG, …)

Conclusion

• Timekeeping accuracy depends on many facts
• Required accuracy depends on applications
• Higher accuracy requires higher effort, and thus solutions are usually more expensive
• Important to find the solution which best meets the requirements of your application

Your Partner for Professional Time and Frequency Synchronization Solutions

Meinberg – Germany

https://www.meinbergglobal.com/

You are Authorized Distributor for Meinberg products in Middle East Region:

Al Mamaas Group – Dubai – UAE

http://almamaas.com/al-mamaas-trading/