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Networking Fundamentals · Foundational

Round-Trip Time (RTT)

The time for a packet to travel to a destination and for the response to return.

Definition

RTT is what ping reports, and TCP measures RTT continuously to set retransmission timeouts. RTT is roughly twice one-way latency on symmetric paths. Bandwidth multiplied by RTT gives the bandwidth-delay product, the amount of data that must be in flight to fill a link.

Example

ping 8.8.8.8 returning time=12ms indicates a 12 ms RTT.

Exam tip

Ping shows round-trip time, not one-way latency.

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