ZyXEL Prestige 660HW-61 External 91-004-370001 Manual Do Utilizador

Prestige 660H/HW Series User’s Guide

Chapter 13 Firewall Configuration

164

Whenever the number of half-open sessions with the same destination host address rises above 
a threshold (TCP Maximum Incomplete), the Prestige starts deleting half-open sessions 
according to one of the following methods:

• If the Blocking Time timeout is 0 (the default), then the Prestige deletes the oldest 

existing half-open session for the host for every new connection request to the host. This 
ensures that the number of half-open sessions to a given host will never exceed the 
threshold. 

• If the Blocking Time timeout is greater than 0, then the Prestige blocks all new 

connection requests to the host giving the server time to handle the present connections. 
The Prestige continues to block all new connection requests until the Blocking Time 
expires. 

The Prestige also sends alerts whenever TCP Maximum Incomplete is exceeded. The global 
values specified for the threshold and timeout apply to all TCP connections. 

Click Firewall, and Threshold to bring up the next screen.

Figure 71   Firewall: Threshold

The following table describes the labels in this screen.

Table 48   Firewall: Threshold 

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 Prestige continues to delete 

half-open sessions as necessary, until the 

rate of new connection attempts drops below 

this number.

80 existing half-open sessions.