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Networking Fundamentals · Intermediate

Sliding Window

A TCP mechanism that lets a sender transmit multiple segments before needing an acknowledgment, with the allowed amount adjusting dynamically.

Definition

The window represents how many unacknowledged bytes may be in flight. As acknowledgments arrive the window slides forward, allowing more data to be sent. Combined with the receive window and congestion window, it lets TCP use available bandwidth while avoiding overload.

Example

With a 64 KB window, a sender can transmit 64 KB before pausing for an ACK.

Exam tip

Windowing is the TCP feature that provides flow control; a larger window raises throughput on high-latency links.

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