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Preventing TCP segment loss in InterScan Web Security Virtual Appliance (IWSVA) 6.5

    • Updated:
    • 26 Sep 2018
    • Product/Version:
    • InterScan Web Security Virtual Appliance 6.5
    • Platform:
    • N/A N/A
Summary

The loss of TCP segments sometimes occur in InterScan Web Security Virtual Appliance 6.5 (IWSVA).

This happens due to some TCP tuning parameters in IWSVA's OS are not appropriate for the current TCP traffic. 

Learn about performance tuning for IWSVA to prevent loss of TCP segments.

Details
Public

The loss of TCP segments occur because the TCP traffic may have reached one of the following limits:

  • The maximum send buffer size (default: 8 MB).
  • The maximum receive buffer size (default: 8 MB).
  • The maximum number of packets in the global input queue for the NIC (default: 1024).

These limits are tuning parameters.

 
If it is difficult to decide "to what extent the size is increased", gradually increase the size to twice, three times then check whether the issue is alleviated.

To change the limits:

  1. Log on to IWSVA as root via SSH (for example with a SSH shell such as PuTTy).
  2. Get a backup copy of /etc/sysctl.conf:

    # cp /etc/sysctl.conf /etc/sysctl.conf.bakorg

  3. Use vi to edit the file /etc/sysctl.conf:

    # vi /etc/sysctl.conf

  4. Change the following values:

    • The maximum send buffer size:

      [Settings (default)]

      ----------------------------------  net.core.wmem_max net.core.rmem_max=8388608  net.ipv4.tcp_wmem net.ipv4.tcp_rmem=4096 262144 4194304  ----------------------------------

      For example: Increase size from 8 MB (default) to 32 MB.

      ----------------------------------   net.core.wmem_max=33554432  net.ipv4.tcp_wmem=4096 262144 33554432  ----------------------------------
    • The maximum receive buffer size:

      [Settings (default)]

      ----------------------------------  net.core.rmem_max=8388608  net.ipv4.tcp_rmem=4096 262144 4194304  ----------------------------------

      For example: Increase the size from 8 MB (default) to 32 MB.

      ----------------------------------   net.core.rmem_max=33554432  net.ipv4.tcp_rmem=4096 262144 33554432  ----------------------------------
    • The maximum number of packets in the global input queue for the NIC (default: 1024):

      [Setting (default)]

      ----------------------------------   net.core.netdev_max_backlog=1024  ----------------------------------

      For example: Increase the size from 1024 (default) to 4096.

      ----------------------------------   net.core.netdev_max_backlog=4096  ----------------------------------
  5. Save the file and quit.
  6. Run the following command.

    # sysctl –p

Premium
Internal
Rating:
Category:
Configure; Troubleshoot
Solution Id:
1121137
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