informalexample-net-tweaks.xml revision 3b574cd1ee8b7536278db5241e8aef5155e371d3
<?xml version="1.0" encoding="UTF-8"?>
<!--
! CCPL HEADER START
!
! This work is licensed under the Creative Commons
! Attribution-NonCommercial-NoDerivs 3.0 Unported License.
! To view a copy of this license, visit
! http://creativecommons.org/licenses/by-nc-nd/3.0/
! or send a letter to Creative Commons, 444 Castro Street,
! Suite 900, Mountain View, California, 94041, USA.
!
! You can also obtain a copy of the license at legal-notices/CC-BY-NC-ND.txt.
! See the License for the specific language governing permissions
! and limitations under the License.
!
! If applicable, add the following below this CCPL HEADER, with the fields
! enclosed by brackets "[]" replaced with your own identifying information:
! Portions Copyright [yyyy] [name of copyright owner]
!
! CCPL HEADER END
!
! Copyright 2014-2015 ForgeRock AS.
!
-->
<informalexample xmlns='http://docbook.org/ns/docbook' version='5.0' xml:lang='en'
xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance'
xsi:schemaLocation='http://docbook.org/ns/docbook
http://docbook.org/xml/5.0/xsd/docbook.xsd'>
<para>
When you do not use the <option>-f</option> option
to keep connections open and rebinds on the connection,
the tool can exhaust the available ports and crash.
You can work around this problem on test systems
by changing TCP settings on the system.
</para>
<para>
For example on Linux systems, set the following parameters
in the <filename>/etc/sysctl.conf</filename> file.
</para>
<programlisting language="ini">
net.ipv4.tcp_fin_timeout = 30
net.ipv4.tcp_tw_recycle = 1
net.ipv4.tcp_tw_reuse = 1
</programlisting>
<para>
The parameter <literal>net.ipv4.tcp_fin_timeout</literal>
sets how long to wait in seconds for a final FIN packet
before forcing a close of the socket.
The default is 60 (seconds).
</para>
<para>
The parameter <literal>net.ipv4.tcp_tw_recycle</literal>
enables fast recycling of TIME_WAIT sockets.
The default is 0 (false).
Enabling this can cause Network Address Translation (NAT) issues.
</para>
<para>
The parameter <literal>net.ipv4.tcp_tw_reuse</literal>
enables reuse of TIME_WAIT sockets for new connections.
The default is 0 (false).
</para>
<para>
These settings are recommended only for testing,
and <emphasis>not for production systems</emphasis>.
</para>
<para>
After making the changes to <filename>/etc/sysctl.conf</filename>,
reload the configuration with the <command>sysctl</command> command.
</para>
<screen>
# sysctl -p
</screen>
</informalexample>