Common abbreviation for TCP Receive Window. RWIN is the amount of data you can buffer(accept) without having to send an acknowledgement to the remote host.
Normally, an RWIN that is too small will cause slow speeds because excessive amounts of acknowledgements have to be sent. But if the RWIN is too big, too much data will have to be retransmitted if there was an error, therefore becoming slower too.
It is therefore important to get the RWIN setting correct to get maximum performance out of your connection.
RWIN
