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Sysctl: Tuning Network Values

Nathan Salt -

PROBLEM

I am running a large Atmail cluster with multiple machines and I have too many TCP connections between hosts or too many in the idle state.

ENVIRONMENT

  • On-Premise Server + WebMail Installations: Version 6.0 > Current Version
  • Webmail Only Installations: Version 6.0 > Current Version

CAUSE

 The systems sysctl values for networking have not been optimized.

RESOLUTION

  1. Open the sysctl.conf file in your editor on the Client Machines
    /etc/sysctl.conf
  2. Apply the below settings:

    Close connections in the TCP FIN timeout state 10 seconds ( default 60 )
    net.ipv4.tcp_fin_timeout = 10

    Increase the range of ports available for client connections ( default 32768 61000 )

    net.ipv4.ip_local_port_range = "15000 61000"
  3. Open the sysctl.conf in your editor on the Server Machines (eg MySQL server or main Installation server)
    /etc/sysctl.conf
  4. Apply the below settings:

    Close connections in the TCP FIN timeout state 10 seconds ( default 60 )
    net.ipv4.tcp_fin_timeout = 10
    The net.core.somaxconn value has an important role. It limits the maximum number of requests queued to a listen socket
    net.core.somaxconn = 1024 ( default 128 )
    net.core.netdev_max_backlog = 2000 ( default 1000 )
  5. Reboot the server machine.
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