o Reflect changed default such that keepalives are always enabled by

  default now.  Discuss why that's good.  Note that there are still
  some situations where turning it off may be advantageous, including
  situations where there are network outages and it's desirable to
  have TCP sessions last beyond the outage.

Reviewed by:	fenner
Suggested by:	silby

1 files changed, 10 insertions, 7 deletions

diff --git a/share/man/man7/tuning.7 b/share/man/man7/tuning.7
index 31443a3..35548df 100644
--- a/share/man/man7/tuning.7
+++ b/share/man/man7/tuning.7
@@ -475,15 +475,18 @@ The
 sysctl determines whether or not the TCP implementation should attempt
 to detect dead TCP connections by intermittently delivering "keepalives"
 on the connection.
-By default, this is only enabled when an application requests it.
-For servers with many network clients and simultaneous connections, we
-recommend that this setting be turned on (set to 1).
-This may be particularly relevent on systems accessed by users
-operating over dialups, as users often disconnect their modems without
-closing active connections.
+By default, this is enabled for all applications; by setting this
+sysctl to 0, only applications that specifically request keepalives
+will use them.
+In most environments, TCP keepalives will improve the management of
+system state by expiring dead TCP connections, particularly for
+systems serving dialup users who may not always terminate individual
+TCP connections before disconnecting from the network.
 However, in some environments, temporary network outages may be
-incorrectly identified as dead sessions, resulting unexpectedly
+incorrectly identified as dead sessions, resulting in unexpectedly
 terminated TCP connections.
+In such environments, setting the sysctl to 0 may reduce the occurrence of
+TCP session disconnections.
 .Pp
 The
 .Va kern.ipc.somaxconn