The loss of TCP segments sometimes occur in InterScan Web Security Virtual Appliance 6.5 (IWSVA).
This happens because some TCP tuning parameters in IWSVA's OS are not appropriate for the current TCP traffic.
This article you how to do some performance tuning for IWSVA in order to prevent the loss of TCP segments.
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.
To change the limits:
- Log on to IWSVA as root via SSH (for example with a SSH shell such as PuTTy).
-
Get a backup copy of /etc/sysctl.conf:
# cp /etc/sysctl.conf /etc/sysctl.conf.bak
-
Use vi to edit the file /etc/sysctl.conf:
# vi /etc/sysctl.conf
-
Change the following values:
-
The maximum send buffer size:
[Settings (default)]
---------------------------------- net.core.wmem_max=8388608 net.ipv4.tcp_wmem=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 ----------------------------------
-
- Save the file and quit.
-
Run the following command.
# sysctl –p
