Choosing between NTP vs GPS time synchronisation is one of the most practical decisions an IT team in Singapore will make. Most organisations know they need accurate synchronised time. Few know where that time actually comes from or why the source matters. Network Time Protocol (NTP) and GPS-disciplined time servers both synchronise your clocks. They are not the same thing. And in Singapore’s regulatory environment across finance, government and critical infrastructure the difference is starting to matter a lot more.

Here is what each one is, how they differ, and how to know which one fits your situation.

How NTP Time Servers Work and When They Are Enough

Network Time Protocol is the internet’s timekeeping standard, around since the mid-1980s and now on its fourth version. Think of it as a hierarchy. At the top sit Stratum 0 devices,  the atomic clocks and GNSS receivers that produce highly accurate time. Stratum 1 servers connect directly to these. Stratum 2 servers sync from Stratum 1, and so on. Each layer adds a small delay, but most enterprise networks run comfortably at Stratum 3 or 4.

Internet NTP works when your server sends a request to a public NTP time source, gets a timestamp back, and adjusts its clock. Simple and free which is good enough for most general IT operations. That time source distributes Coordinated Universal Time (UTC), the global standard all networks trace back to. The NTP server becomes the reference. Every device that syncs to it becomes a slave clock, inheriting its time from one step up the hierarchy.

But the internet is not a controlled environment, congestion, routing changes and variable delays all affect accuracy. Over the internet, the number can drift to tens of milliseconds depending on the conditions, but for most systems it is fine.

How GPS Time Servers Use GNSS Satellites and Atomic Clocks

GNSS satellites including GPS, GLONASS and Galileo, they all carry atomic clocks on board. Each satellite broadcasts its position and the precise time of transmission. Each one broadcasts a signal with its precise location and the time of transmission. A receiver on the ground listens to at least four satellites simultaneously and calculates the exact time by measuring signal travel time at the speed of light.

A GPS time server picks up that signal, processes it, and distributes time across your local network via NTP. The clock configuration is straightforward. One GPS-disciplined time server at the top. Every switch, server and device on your network syncing to it below. The accuracy of atomic clocks reaches every endpoint without the cost of an atomic clock at every endpoint.

The path is: satellite → your antenna → your server → your devices.

GPS-disciplined servers typically achieve accuracy of around 100 nanoseconds while internet NTP is accurate to tens of milliseconds. That’s roughly 100,000 times the difference!

How to Choose the Right Time Server For Your Organisation— NTP vs GPS

1. How accurate do you actually need to be?

For general IT infrastructure like servers, workstations, access control, CCTV, routine log management, NTP is sufficient. A well-configured NTP time server with properly set up slave clocks will keep most enterprise systems within a few milliseconds of each other. Clocks staying within a few milliseconds of each other is sufficient for those systems to interoperate reliably.

For finance, telecommunications, power grid management, or any system where transaction ordering or regulatory timestamp compliance matters, milliseconds are not enough. For financial institutions (including those operating under MAS Technology Risk Management guidelines), their transaction ordering and audit trail integrity matter, and the accuracy and traceability that GPS provides is the safer choice.

2. What happens to your time if the internet goes down?

Internet NTP needs a live internet connection to a reachable server.

A GPS server has no internet dependency and it receives satellite signals regardless. Most enterprise GPS servers also include a holdover oscillator that keeps the site synchronised for hours or days if the satellite signal is temporarily unavailable.

3. Can you trace and audit your time source?

This is where things get important for regulated industries. Internet NTP passes through multiple intermediary servers you do not control and cannot always verify. On the other hand, GPS is end-to-end as your receiver to the satellite, with a short and documentable chain back to international atomic clock standards. 

4. What is your exposure to network-based attacks?

NTP uses well-known ports and requires bidirectional firewall access, which creates exposure to reflection and amplification attacks. The exposure exists by design, because the protocol requires network access. GPS is receive-only and It sends nothing. There is no port to exploit, no upstream server to spoof, and no internet path an attacker can manipulate.

The most common answer for Singapore organisations in regulated sectors is both. A GPS time server at Stratum 1 acts as the on-site authority. Every other device on the network syncs to it over NTP. You get GPS-level accuracy distributed across thousands of endpoints without needing a GPS receiver at each one. One GPS time server. Every clock on your network disciplined to the same atomic clock source.