ZyXEL Communications ZyWALL5UTM 4.0 User Manual

ZyWALL 5/35/70 Series User’s Guide

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Chapter 11 Firewall Screens

Figure 101   Firewall Threshold

The following table describes the labels in this screen.  

Table 72   Firewall Threshold 

Disable DoS Attack 

Protection on

Select the check box of an interface to which the ZyWALL does not apply the 

thresholds. This disables DoS protection on the selected interface.

Denial of Service 

Thresholds

One Minute Low

This is the rate of new half-open sessions that causes the firewall to stop deleting 

half-open sessions. The ZyWALL continues to delete half-open sessions as 

necessary, until the rate of new connection attempts drops below this number.

One Minute High

This is the rate of new half-open sessions that causes the firewall to start deleting 

half-open sessions. When the rate of new connection attempts rises above this 

number, the ZyWALL deletes half-open sessions as required to accommodate 

new connection attempts.
The numbers, say 80 in the One Minute Low field and 100 in this field, cause the 

ZyWALL to start deleting half-open sessions when more than 100 session 

establishment attempts have been detected in the last minute, and to stop 

deleting half-open sessions when fewer than 80 session establishment attempts 

have been detected in the last minute.

Maximum 

Incomplete Low

This is the number of existing half-open sessions that causes the firewall to stop 

deleting half-open sessions. The ZyWALL continues to delete half-open requests 

as necessary, until the number of existing half-open sessions drops below this 

number.