In data communications, when a receiver receives a message, it sends an acknowledgement back to the sender to notify it about correct receipt of the message. Cumulative acknowledgement is a process in which the receiver sends a single acknowledgement in response to a finite number of frames received. Through this, the receiver acknowledges that it has correctly received all previous frames or packets. When the sender receives an acknowledgement for frame n, it understands correct delivery of frames n – 1, n – 2 and so on.
Cumulative acknowledgement is used along with sliding window protocols. It reduces the time and bandwidth wasted for sending acknowledgement.
The following flow diagram shows cumulative acknowledgements for a set of frames versus independent acknowledgments for each frame.