ZyXEL Communications 660HW Series - Manual (Page 165)

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 75 Firewall: Threshold
The following table describes the labels in this screen.
Table 47 Firewall: Threshold
LABEL DESCRIPTION DEFAULT VALUES
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.