What is Round-trip Time (RTT)?

One of our most viewed dashboard metrics, round-trip time (RTT) is the time it takes for a packet to go from the sending endpoint to the receiving endpoint and back.

There are many factors that affect RTT, including propagation delay, processing delay, queuing delay, and encoding delay. These factors are generally constant for a given pair of communicating endpoints. In addition, network congestion can add a dynamic component to RTT.  

Propagation delay is usually the dominant component in RTT. It ranges from a few milliseconds to hundreds of milliseconds depending on whether the endpoints are separated by a few kilometers or by an entire ocean.

The remaining components (processing, queuing, and encoding delays) can vary by the number of nodes in the network connecting endpoints. When only a few router hops separate endpoints, these factors are negligible.