Threshold Values; Configuring Firewall Thresholds - ZyXEL Communications P-660HW-Tx v3 User Manual

Chapter 9 Firewalls

9.4.1 Threshold Values

If everything is working properly, you probably do not need to change the
threshold settings as the default threshold values should work for most small
offices. Tune these parameters when you believe the ZyXEL Device has been
receiving DoS attacks that are not recorded in the logs or the logs show that the
ZyXEL Device is classifying normal traffic as DoS attacks. Factors influencing
choices for threshold values are:
The maximum number of opened sessions.
1
The minimum capacity of server backlog in your LAN network.
2
The CPU power of servers in your LAN network.
3
Network bandwidth.
4
Type of traffic for certain servers.
5
Reduce the threshold values if your network is slower than average for any of
these factors (especially if you have servers that are slow or handle many tasks
and are often busy).
• If you often use P2P applications such as file sharing with eMule or eDonkey, it's
recommended that you increase the threshold values since lots of sessions will
be established during a small period of time and the ZyXEL Device may classify
them as DoS attacks.

9.4.2 Configuring Firewall Thresholds

The ZyXEL Device also sends alerts whenever TCP Maximum Incomplete is
exceeded. The global values specified for the threshold and timeout apply to all
TCP connections.
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P-660HW-Tx v3 User's Guide