Self TCP

Question

Why one of the causes of Silly Window Syndrome is when the server announces an empty space of 0?

I understand the other two cases that is when 

1. When client is able to generate only 1 byte at a time
2. When server is able to consume only 1 byte at a time.

But why the third one?

https://en.wikipedia.org/wiki/Silly_window_syndrome#Solution

Answer 1

Consider a scenario where a SERVER is communicating with multiple CLIENTs and these CLIENTs have large amount of data to send.

Now, for whatsoever reason, suppose that SERVER is bogged up and all the communication have gone in SWS phase(2^nd case).

All the CLIENTs still have data to send. Now CLIENT₁ sends data, after comsuming that packet, if receiver buffer at SERVER becomes less than the minimum packet size, it sends ACK to CLIENT₁ with receiver window = 0.

CLIENT₁ still have data to send, so it sends a dummy packet to ask for new receiver window size. But within this time, other CLIENTs are sending some data and again filling up receiver window. So, SERVER has to send receiver window size of 0 to CLIENT₁​​​​​​​ .

Look at the communication between CLIENT₁​​​​​​​ and SERVER. SERVER is continuosly sending window size of 0 and leading communication to SWS.