[TCP] Sysctl documentation: tcp_frto_response

	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.