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Add description of the keepalives option

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[originally from svn r1166]
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Simon Tatham 2001-08-04 13:05:54 +00:00
parent 4fb01728e1
commit 5138551608
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doc/config.but
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@ -530,6 +530,48 @@ more than one type of connection.
\S{config-keepalive} Using keepalives to prevent disconnection
If you find your sessions are closing unexpectedly (\q{Connection
reset by peer}) after they have been idle for a while, you might
want to try using this option.
Some network routers and firewalls need keep track of all
connections through them. Usually, these firewalls will assume a
connection is dead if no data is transferred in either direction
after a certain time interval. This can cause PuTTY sessions to be
unexpectedly closed by the firewall if no traffic is seen in the
session for some time.
The keepalive option (\q{Seconds between keepalives}) allows you to
configure PuTTY to send data through the session at regular
intervals, in a way that does not disrupt the actual terminal
session. If you find your firewall is cutting idle connections off,
you can try entering a non-zero value in this field. The value is
measured in seconds; so, for example, if your firewall cuts
connections off after ten minutes then you might want to enter 300
seconds (5 minutes) in the box.
Note that keepalives are not always helpful. They help if you have a
firewall which drops your connection after an idle period; but if
the network between you and the server suffers from breaks in
connectivity then keepalives can actually make things worse. If a
session is idle, and connectivity is temporarily lost between the
endpoints, but the connectivity is restored before either side tries
to send anything, then there will be no problem - neither endpoint
will notice that anything was wrong. However, if one side does send
something during the break, it will repeatedly try to re-send, and
eventually give up and abandon the connection. Then when
connectivity is restored, the other side will find that the first
side doesn't believe there is an open connection any more.
Keepalives can make this sort of problem worse, because they
increase the probability that PuTTY will attempt to send data during
a break in connectivity. Therefore, you might find they help
connection loss, or you might find they make it worse, depending on
what \e{kind} of network problems you have between you and the
server.
Keepalives are only supported in Telnet and SSH; the Rlogin and Raw
protocols offer no way of implementing them.
\H{config-telnet} The Telnet panel
The Telnet panel allows you to configure options that only apply to