Draw a timeline diagram for the sliding window algorithm...

Draw a timeline diagram for the sliding window algorithm with SWS = RWS = 3 frames for the following two situations. Use a timeout interval of about $2 \times \mathrm{RTT}$.
(a) Frame 4 is lost.
(b) Frames 4-6 are lost.

Key Concepts

Round Trip Time (RTT)

Round Trip Time is the time it takes for a signal to be sent from the sender to the receiver and for the acknowledgment of that signal to be received back at the sender. It is a crucial metric in determining the appropriate timeout interval for retransmissions, providing a basis (typically using a multiple like 2×RTT) for timing decisions in reliable data transmission protocols such as the sliding window protocol.

Frame Loss and Retransmission

Frame loss refers to the situation where one or more frames do not reach the receiver, which can be due to network congestion, errors, or other impairments. In protocols that use the sliding window method, when a frame is lost, the timeout mechanism triggers a retransmission of the unacknowledged frames, ensuring that data integrity is maintained despite losses during transmission.

Sliding Window Protocol

This is a method used in data communication where the sender can transmit multiple frames before needing an acknowledgment for the first frame, effectively using a 'window' of unacknowledged frames. The protocol adjusts this window as frames are sent, acknowledged, or need to be retransmitted, promoting efficiency and reliability in the transmission process.

Timeout Mechanism

A timeout mechanism is employed to detect lost frames; if an acknowledgment (ACK) is not received within a predefined period, the sender presumes that the frame (or frames) was lost and triggers a retransmission. Here, the timeout interval is typically set around double the round trip time (2×RTT) to accommodate network delays and ensure that transient conditions do not cause premature retransmission.

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