Creating a Time-synchronization master

This article is written for those interested in latency, especially those using the Wireless Endpoint or across multiple ByteBlower Servers. The quality of the latency measurements strongly depends on having a high-quality time reference.

This is especially visible in the one-way latency measurements of ByteBlower server and Wireless Endpoint. Yet this tool provides invaluable information on network under test. With FrameBlasting you receive throughput and latency information for each direction and for each traffic-flow.

• This makes any asymmetry in either direction clearly visible.
• It allows you to evaluate the active queue management (AQM) behaviour.
• With sufficient Endpoints, individual hops can be characterized.

Yet measuring such latency values across distributed setups poses a particular challenge. To this end this text explains how to set up a qualitative time synchronization that solves these difficulties.

Why time-synchronization for latency measurements?

Latency of the traffic is the time-interval between transmitting the packet and next receiving somewhere else. Measuring this duration requires a sufficient fine timestamp to of each. In case of a single system, with a single clock, this calculation is straightforward. It is in shown in the picture below.

The time-axis at the center represents the clock on the ByteBlower Server. The packet is transmitted at the left side of the figure, it passes through the “Network under Test” and is received further down the time-axis.