[TCP] Sysctl documentation: tcp_frto_response

In addition, fixed minor things in tcp_frto sysctl.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 719b42907314e7934d0470c7205218f21f084d36..054c515bd7265e728d379c37d98c689712844cd7 100644 (file)
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -179,15 +179,32 @@ tcp_fin_timeout - INTEGER
        because they eat maximum 1.5K of memory, but they tend
        to live longer. Cf. tcp_max_orphans.
 
-tcp_frto - BOOLEAN
+tcp_frto - INTEGER
        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. If set to 1, basic
-       version is enabled. 2 enables SACK enhanced FRTO, which is
+       version is enabled. 2 enables SACK enhanced F-RTO, which is
        EXPERIMENTAL. The basic version can be used also when SACK is
        enabled for a flow through tcp_sack sysctl.
 
+tcp_frto_response - INTEGER
+       When F-RTO has detected that a TCP retransmission timeout was
+       spurious (i.e, the timeout would have been avoided had TCP set a
+       longer retransmission timeout), TCP has several options what to do
+       next. Possible values are:
+               0 Rate halving based; a smooth and conservative response,
+                 results in halved cwnd and ssthresh after one RTT
+               1 Very conservative response; not recommended because even
+                 though being valid, it interacts poorly with the rest of
+                 Linux TCP, halves cwnd and ssthresh immediately
+               2 Aggressive response; undoes congestion control measures
+                 that are now known to be unnecessary (ignoring the
+                 possibility of a lost retransmission that would require
+                 TCP to be more cautious), cwnd and ssthresh are restored
+                 to the values prior timeout
+       Default: 0 (rate halving based)
+
 tcp_keepalive_time - INTEGER
        How often TCP sends out keepalive messages when keepalive is enabled.
        Default: 2hours.