diff --git a/src/backend/libpq/pqcomm.c b/src/backend/libpq/pqcomm.c
index 34efac4..711ca2f 100644
--- a/src/backend/libpq/pqcomm.c
+++ b/src/backend/libpq/pqcomm.c
@@ -713,6 +713,8 @@ StreamConnection(pgsocket server_fd, Port *port)
 	if (!IS_AF_UNIX(port->laddr.addr.ss_family))
 	{
 		int			on;
+		int			oldopt;
+		int			optlen;
 
 #ifdef	TCP_NODELAY
 		on = 1;
@@ -734,16 +736,34 @@ StreamConnection(pgsocket server_fd, Port *port)
 #ifdef WIN32
 
 		/*
-		 * This is a Win32 socket optimization.  The ideal size is 32k.
+		 * This is a Win32 socket optimization.  The ideal size is 32k except
+		 * for Windows 2012(and later versions).
 		 * http://support.microsoft.com/kb/823764/EN-US/
+		 * On Windows 2012, the default TCP send buffer size is 64k and with 
+		 * dynamic send buffering. And, the default setting is better.
+		 * (Note:Dynamic send buffering will be disabled if sets the SO_SNDBUF
+		 * socket option.)
+		 * https://msdn.microsoft.com/en-us/library/windows/desktop/bb736549(v=vs.85).aspx
+		 * On Windows 2008(and earlier versions), the default TCP send buffer
+		 * size is 8k, enlarging it to 32k is better.
 		 */
-		on = PQ_SEND_BUFFER_SIZE * 4;
-		if (setsockopt(port->sock, SOL_SOCKET, SO_SNDBUF, (char *) &on,
-					   sizeof(on)) < 0)
+		optlen = sizeof(oldopt);
+		if (getsockopt(server_fd, SOL_SOCKET, SO_SNDBUF, (char *) &oldopt,
+					   &optlen) < 0)
 		{
-			elog(LOG, "setsockopt(SO_SNDBUF) failed: %m");
+			elog(LOG, "getsockopt(SO_SNDBUF) failed: %m");
 			return STATUS_ERROR;
 		}
+		on = PQ_SEND_BUFFER_SIZE * 4;
+		if(oldopt < on)
+		{
+			if (setsockopt(port->sock, SOL_SOCKET, SO_SNDBUF, (char *) &on,
+						   sizeof(on)) < 0)
+			{
+				elog(LOG, "setsockopt(SO_SNDBUF) failed: %m");
+				return STATUS_ERROR;
+			}
+		}
 #endif
 
 		/*