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
This commit is contained in:
rwatson 2001-12-06 20:24:38 +00:00
parent 31c6261195
commit f1d0f5e5bf

View File

@ -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