Does windows TCP stack sends ACK when the packet is received by the kernel or after the socket read?

Question

I understand that in most UNIX based systems, as soon as the kernel receives the packet it sends the ACK. But would like to know if the behavior is same in windows operating system too. (Windows 7).

Answer 1

The behaviour is the same in all operating systems. It is defined by RFC 793. ACK is performed when (or, in the case of a delayed ACK, after) the data is received by TCP. It has nothing to do with when the application reads.