
128 Data Communications and Computer Networks
numbered from 0 to 6 without having to wait for any ACK from B and B can receive frames numbered from
0 to 6 from A, respectively. As the frames are sent or received at the sender’s and receiver’s end respec-
tively, the window size shrinks. For example, after transmitting frames F0, F1, F2 and F3, the size of A’s
window shrinks to three frames and after receiving frames F0, F1, F2 and F3, the size of B’s window
shrinks to three frames (Figure 7.2). Similarly, the window size expands as the ACKs are received or sent
by the sender and receiver, respectively. Therefore, the scheme is named as sl