How To Sync A Network Using NTP

PC's maintain time using internal real-time clock chips. These are relatively low cost devices that do not keep very good time. They can drift by seconds or even minutes each day. This can cause real headaches when events need to be ordered across a number of computers on a network. Synchronisation of computers and infrastructure across a network is a necessity in modern computing environments. Networked event logging, transaction processing and security systems all rely on synchronised time.

This article describes how easy it is to synchronise servers, workstations and network infrastructure to a precise time reference. NTP time servers allow all the servers, workstations and other infrastructure on a network to synchronise to a single precise reference. A Time Server obtains accurate timing information from an external time reference and maintains a precise internal time. This precise time is then made available to network clients for synchronisation purposes.

NTP or Network Time Protocol is the standard means of network time synchronisation over TCP/IP networks. It defines a number of packets of information that are passed between a Server and client in order to achieve synchronisation. Most modern operating systems, including Windows, Novell and Linux all have integrated NTP client software. Additionally, a timing daemon is also freely downloadable from the dedicated NTP website.

Configuration the client software is very straightforward. The client only needs the IP address of the network time server that the client is to utilise.

There are many Internet based NTP Servers that are freely available for public use. However, there are a number of advantages to having a local server on your network. Firstly, a local server will reside inside your firewall and pose less of a security risk than an Internet based server. Also, local servers tend to be more accurate by having a direct connection to an external timing reference without any network round-trip-delays. Additionally, Internet based servers are often configured incorrectly and can provide inaccurate time.

There are a number of external reference clocks available to time servers, the most common and most accurate being the Global Positioning System (GPS). GPS can provide time accurate to within a few nanoseconds. However, a GPS antenna is required that needs to have a good view of the sky, ideally on a rooftop. Therefore, installation costs can be an inhibiting factor. An alternative solution is a radio time reference. Radio time and frequency broadcasts can generally be received indoors close to the host server. Installation costs are therefore significantly reduced. However, weather and other forms of interference can affect radio broadcasts. Also, radio time references are not as accurate as time sourced from GPS.

Synchronising a computer network and its associated infrastructure is very straightforward. There are solutions available for every budget, from free to use internet based time references to dedicated NTP time servers.