Question : TCP flow control

Sir/Madam,
 
I was studying the subject of TCP flow control and I’ve a small question. I’ll get on to the question right away.
 
REFERENCE:
"A TCP MAY keep it’s offered receive window closed indefinitely.  As long as the receiving TCP continues to send acknowledgments in response to the probe segments, the sending TCP MUST allow the connection to stay open.
"http://www.rfc-editor.org/rfc/rfc1122.txt? Page 91, last visited Sep27 2002
 
BACKGROUND:
Once the sender knows that the receiver’s window size is zero. The specification says that the sender sends these probe segments to the receiver, in order to be able to receive an acknowledgement from the receiver, which contains the receiver’s window piggybacked in the ACK segment if the window opens at a later instance.
 
QUESTION:
Why is the sender required to probe the receiver continuously. Is it not possible that the receiver on its own sends a segment to the sender, piggybacking the receiver’s window size, once it knows that there is free space in it incoming buffer? Would it not be efficient this way? And if so, why does the TCP require implementations to send probe segments.
 
Regards,
Maneesh Khattri.

Answer : TCP flow control

Think this way:
in the last segment received, window size is set to 0 which states that receiver does not want to receive any more data, probably it does not have enough power or processing power, etc. however the sender has some more data to send.

during this time guess that receiver crashes.

if the sender does not probe the receiver, it waits indefinitely for the receiver to increase its window size in order for the sender to send its data.

hope this helps
regards