Time Synchronization

Time Synchronization White Paper

One-way testing of an Ethernet path through a network with test instruments at each end of the path gives detailed information on performance and issues for the two directions of the path. If the path is asymmetrical one-way testing is essential to identify the downlink and uplink throughput for the path.

A parameter that is very relevant for the one-way test is the latency of the path under test. However one-way latency measurements involving two test instruments require that the clock systems of the two instruments are synchronized. Likewise multi-site protocol analysis requires that the clocks of all instruments capturing data packets are synchronized. The same applies when synchronized traffic start on a number of test instruments is required.

Several solutions exist for synchronizing clocks in test instruments (and other devices). Each instrument can be equipped with a Global Positioning System (GPS) receiver, which can give precise, synchronized time information to instruments. Alternatively time synchronization can be based on the Network Time Protocol (NTP) or the Precision Time Protocol (PTP).

ValkyrieTimeSync synchronizes time for the Xena Networks layer 2-3 test solutions ValkyrieBay and ValkyrieCompact. ValkyrieTimeSynch is a flexible and powerful time synchronization solution that supports GPS, PTP and NTP. With ValkyrieTimeSynch the Xena tester acts as a client that is synchronized to a PTP/NTP time server or to the GPS. ValkyrieTimeSynch can also turn a Xena tester into a PTP/NTP time server that can synchronize other testers.

This White Paper explains how syncronized latency measurements can be made with multiple instruments using different synchronization methods, like Global Positioning System (GPS), Precision Time Protocol (PTP) or the Network Time Protocol (NTP).