What is the silly window syndrome?
The silly window syndrome results when the sender can send data faster than the reciever can handle it, and the receiver calls recv() with very small buffer sizes. The fast sender will quickly fill the receiver’s TCP window. The receiver then reads N bytes, N being a relatively small number compared to the network frame size. A naïve stack will immediately send an ACK to the sender to tell it that there are now N bytes available in its TCP window. This will cause the sender to send N bytes of data; since N is smaller than the frame size, there’s relatively more protocol overhead in the packet compared to a full frame. Because the receiver is slow, the TCP window stays very small, and thus hurts throughput because the ratio of protocol overhead to application data goes up. The solution to this problem is the delayed ACK algorithm. This causes the window advertisement ACK to be delayed a bit, hopefully allowing the slow receiver to read more of the enqueued data before the ACK goes out.
