NTP (Network Time Protocol) hardware refers to dedicated devices that provide accurate, traceable time to a computer network. Unlike software-only NTP clients, which sync to internet servers, hardware NTP server devices usually have their own atomic or GPS-based time source. They are used where high accuracy, reliability, or security is critical such as finance, telecom, data centers, broadcast, and industrial systems.
Key Hardware Components
A number of hardware components are critical to providing an accurate and reliable source of time using NTP.
Source Of Time
A reliable source of accurate time is essential to maintain precise and reliable time synchronization.
Global Navigation Satellite System (GNSS)
NTP server hardware devices often use GNSS time sources, to provide precise and reliable time synchronization.
A GNSS receiver module obtains accurate time from satellites. The receiver connects to an NTP server, typically a Linux host or dedicated time appliance. The NTP server uses the GNSS input as its Stratum 0 reference clock. Other network devices synchronize via NTP to that server and become lower stratum devices.
The GPS (Global Positioning System) is the most common time reference, receiving precise UTC time from satellites. Higher-end Multi-GNSS (Multi-Constellation) systems often support reception of GPS (US), Galileo (EU), GLONASS (Russia) and BeiDou (China) for redundancy.
Most GNSS signals can be received world-wide.
Radio Time and Frequency Broadcasts.
Radio time and frequency broadcasts are radio transmissions that carry precise time and frequency information, allowing clocks, navigation systems, and scientific instruments to stay synchronized with national or international time standards (like UTC).
Major time signal stations around the world include: WWV (Colorado, USA), MSF (Anthorne, UK), DCF-77 (Mainflingen, Germany) and JJY (Fukushima, Japan).
These signals are generated by national metrology institutes that maintain atomic clocks. Generally, the signals can only be received within national boundaries. Unlike GNSS transmissions which can be received globally. Signal reception can also be dependent on local geographical topology.
High Stability Oscillator (Internal Clock)
Many computer devices, such as PC’s and laptops, incorporate a regular crystal oscillator (XO) which generates a stable frequency using the mechanical resonance of a quartz crystal. However, the frequency of a regular crystal oscillator can drift when the temperature changes. Frequency drift will lead to time drift if Stratum-0 time references are lost for even short durations.
There are a number of much more stable oscillators available which can maintain a much more accurate time.
TCXO (Temperature Compensated Crystal Oscillator)
A TCXO is a Temperature-Compensated Crystal Oscillator. It is a type of crystal oscillator designed to maintain a very stable output frequency over a wide range of temperatures.
A TCXO includes a temperature sensor that continuously monitors temperature. Then, using an electronic compensation circuit, it adjusts the oscillator’s control voltage to counteract the temperature-induced frequency drift.
TCXO’s provide a great cost-performance trade-off.
OCXO (Oven Controlled Crystal Oscillator)
An OCXO is an Oven-Controlled Crystal Oscillator. An OCXO reduces frequency drift by enclosing the crystal, and often part of the control circuitry, in a temperature-controlled miniature oven. The oven keeps the crystal at a constant, elevated temperature, typically around 60–85 °C, so external temperature fluctuations don’t affect its frequency.
OCXO have better stability and drift performance than TCXO’s but are much more expensive.
Rubidium Oscillator
A Rubidium oscillator, often called a Rubidium frequency standard or Rubidium atomic clock, is a highly precise time and frequency reference device that uses the natural resonant frequency of rubidium atoms to maintain an extremely stable output signal.
A basic Rubidium Oscillator Module can cost as much as USD 3,000, while a High-Performance Rubidium Frequency Standard can cost as much as USD 10,000. However, Rubidium oscillators have a rubidium lamp that degrades over time, with a typical lifespan of around 8 to 15 years.
These high-cost oscillators provide amongst the highest accuracy and long-term holdover.
Network Interface
Network Time Protocol is a standard protocol for disseminating time to a network, therefore NTP hardware requires a network interface to connect to a network. Typically a 10/100 Mbps or gigabit (GbE) interface is used. Sometimes multiple Ethernet interfaces are used for segmentation or redundancy.
Supported Protocols
NTP server hardware will need to support the Network Time Protocol in order to synchronize clients.
NTP has complex, advanced algorithms to handle jitter and packet round-trip delay compensation. While SNTP has much simpler algorithms which require far fewer calculations. Most servers will also support SNTP, Simple Network Time Protocol. It is a simplified version of NTP (Network Time Protocol), which is used to synchronize the clocks of computers and other devices over a network.
NTP has millisecond-level accuracy, ideal for servers, routers and critical systems. While SNMP accuracy is sufficient for IoT devices and simple embedded systems.
Support for TCP/IP and UDP is also necessary to implement NTP. While HTTPS, Syslog, SSH and SNMP protocols are required for configuration, management and monitoring purposes.
Security
NTP Authentication (MD5, SHA)
NTP Authentication refers to the security mechanisms used in the Network Time Protocol (NTP) to ensure that time synchronization messages exchanged between clients and servers are genuine and unaltered. Without authentication, anyone could spoof NTP packets, potentially shifting system clocks.
NTP authentication ensures that the NTP client knows the server is legitimateand that the message has not been modified in transit.
How NTP Hardware Works
NTP hardware operates in the following manner:
- Receives UTC from GPS or other sources.
- Disciplines the internal oscillator which keeps the device stable even if GNSS signals drop out.
- Distributes time to clients over the LAN using NTP.
- Acts as a Stratum 1 server, meaning it is directly linked to an authoritative UTC source.
- Clients synchronise typically as Stratum 2 devices from the hardware server.
Installation and Setup
Briefly, the installation and setup consists of:
- Installing the antenna. Ideally a GPS/GNSS antenna should be installed with a clear 360 degree sky view.
- Use low-loss coaxial cable (e.g., LMR195 or LMR400) between NTP server hardware and antenna.
- A lightning arrestor or surge suppressor is recommended for outdoor located antennas.
- Rack-mount device and connect.
- Configure via web or console interface.
- Set IP address, network mask and gateway and any required NTP parameters. Static IP recommended for predictability.
- Enable NTP service, configure authentication keys if needed.
- Connect clients.
- Point NTP clients to the server’s IP.
NTP Hardware Best Practices
There are a number of Network Time Protocol (NTP) Hardware best practices for accurate, secure, and reliable time synchronization across systems:
Install multiple NTP servers for redundancy.
Use at least 3 upstream NTP servers to detect and correct anomalies..
Protect with firewalls and authentication.
Use symmetric keys to authenticate trusted servers. Allow only NTP UDP port 123 to/from known NTP peers. If possible, disable mode 6/7 control queries unless required.
Regularly check GPS signal strength and antenna condition.
Check GPS signal status information for a strong signal from multiple satellites. Ensure that any outdoor located antenna is in good condition and provides a good unobscured view of the sky.
Monitor via SNMP or Syslog for faults.
Use SNMP or monitor Syslog entries to ensure synchronization is consistently maintained.
Secure Your NTP Traffic.
Use restrict directives in the NTP configuration file to limit queries, control time service access.
Ensure firmware is up to date.
Check that the latest NTP firmware and GNSS reference clock drivers are being utilised.
Accurately synchronise the time on computers and network infrastructure in your organization with TimeTools TA310 GPS Network Time Server. The TA310 is designed and manufactured in the UK, and provides:
- Advanced, 92 Channel, GPS Receiver For Reliable Reception Of The GPS Satellite System.
- Security-Hardened, Enterprise-Class, Stratum-1 NTP v4 Network Time Server.
- Ultra-Fast, 50,000 NTP Polls Per Second (3M Per Minute), For Precise Client Synchronization.
- High-Stability, Temperature-Compensated Crystal Oscillator (TCXO) For Extended Stratum-1 Operation In The Event Of Any Loss of GPS Signal Lock.
- Network-Optimized Gigabit Ethernet (GbE).
- Powerful, Easy To Use, Web Interface With Command Line Interface For Advanced Users.
- CE and UKCA Compliant With Full EMC and Electrical Safety Test Reports.