diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 702d1d8dd04a1261b598a0370095df1cbfc0899e..719b42907314e7934d0470c7205218f21f084d36 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -183,7 +183,10 @@ tcp_frto - BOOLEAN
 	Enables F-RTO, an enhanced recovery algorithm for TCP retransmission
 	timeouts.  It is particularly beneficial in wireless environments
 	where packet loss is typically due to random radio interference
-	rather than intermediate router congestion.
+	rather than intermediate router congestion. If set to 1, basic
+	version is enabled. 2 enables SACK enhanced FRTO, which is
+	EXPERIMENTAL. The basic version can be used also when SACK is
+	enabled for a flow through tcp_sack sysctl.
 
 tcp_keepalive_time - INTEGER
 	How often TCP sends out keepalive messages when keepalive is enabled.