Network Time Server and NTP Server: FAQ

Why do I need a Time Server?

One of the most common problems associated with modern computers is to know, with some degree of certainty, what the correct time is. The first problem is the clock in the computer. Most computers use a simple crystal oscillator time base that is often imprecise, very temperature sensitive, and exhibits significant frequency change over time. The second problem is how to set the clock. Most computers allow the user to set the clock manually. Setting the clock to an accuracy of one second is difficult at best. The third problem is what is the reference used to determine what the correct time is in the first place. When two or more computers are involved, especially if they are not in the same physical location, accurate time keeping is difficult indeed. A network time server supplies the solution to each of the three problems even when many computers are involved.

How do Time Servers work?

A time server is a precision clock that can be accurately synchronized to an external source of time. Additionally, hardware and software is included that transmits the accurate time to the client computers.

The Brandywine Communications Network Time Servers synchronize their internal clocks to the GPS satellite system. The GPS system ensures time transfer to better than one-microsecond anywhere in the world. Internal to the time server is a bundle of software called the Network Time Protocol (NTP). A small NTP client program is installed into the computers to be synchronized. Once the IP address, sub-net mask and gateway addresses are loaded into the client computer(s) the time synchronization is automatic. The NTP server and clients periodically communicate in order to transfer the time from the server to the client(s). The number of clients is essentially unlimited. The accuracy of the time transfer is about 100 milliseconds in PC applications and in the order of hundreds of microseconds in workstation applications. The improved performance in workstations is because high-end workstations have oscillators that can be disciplined, that is have their clock frequency adjusted. In large networks traffic on the network can delay the NTP messages. The NTP software calculates the latency of the time transfer and provides latency correction.

Why not use the network time services available over the Internet?

There are several time servers available on the Internet. Using them for precise time is not recommended for the following reasons:

• Network conditions may prevent time from being disseminated.
• Distance from the server may create indeterminate network latency variables.
• The client has no way to trace the time to its ultimate time source.
• Security firewalls are often required.

How many time servers do I need?

Usually only one time server per LAN is required. One time server can synchronize many client computers. In order to provide the highest level of security and reliability it is best to locate the time server on the client side of the firewall.

Are network time servers easy to install and are they reliable?

The time servers from Brandywine Communications are simple to install; connect the power, connect the antenna, set in the IP address, sub-net make and gateway address, connect the server to the network, install the client program in the client computers and the job is done.

All Brandywine Communications network time server products have proven to be extremely reliable. Years of trouble-free operation have been demonstrated and are to be expected.

Is network security compromised?

No, a time server is a network product like a printer or file server. The only external connections are to power, the network and the antenna in GPS models. In GPS installations with very high security requirements, TEMPEST for example, a fiber optic antenna installation kit is available.