TCP/IP 详解 卷1 ch20 TCP Bulk Data Flow

1. 滑动窗口协议

 

1） The window closes as the left edge advances to the right. This happens when data is sent and acknowledged.

2） The window opens when the right edge moves to the right, allowing more data to be sent. This happens when the receiving process on the other end reads acknowledged data, freeing up space in its TCP receive buffer.

3） The window shrinks when the right edge moves to the left.

 

2. 总结滑动窗口

 

1） The sender does not have to transmit a full window's worth of data.

2） One segment from the receiver acknowledges data and slides the window to the right. This is because the window size is relative to the acknowledged sequence number.

3） The size of the window can decrease, but the right edge of the window must not move leftward.

4） The receiver does not have to wait for the window to fill before sending an ACK. We saw earlier that many implementations send an ACK for every two segments that are received.