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Chapter 7 Firewalls
P-660R-F1 Series User’s Guide
98
The following table describes the labels in this screen.
Table 36
Security > Firewall > Threshold
LABEL
DESCRIPTION
Denial of Service
Thresholds
The ZyXEL Device measures both the total number of existing half-open
sessions and the rate of session establishment attempts. Both TCP and UDP
half-open sessions are counted in the total number and rate measurements.
Measurements are made once a minute.
One Minute Low
This is the rate of new half-open sessions per minute that causes the firewall to
stop deleting half-open sessions. The ZyXEL Device 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 per minute that causes the firewall to
start deleting half-open sessions. When the rate of new connection attempts
rises above this number, the ZyXEL Device deletes half-open sessions as
required to accommodate new connection attempts.
For example, if you set the one minute high to 100, the ZyXEL Device starts
deleting half-open sessions when more than 100 session establishment
attempts have been detected in the last minute. It stops deleting half-open
sessions when the number of session establishment attempts detected in a
minute goes below the number set as the one minute low.
Maximum
Incomplete Low
This is the number of existing half-open sessions that causes the firewall to stop
deleting half-open sessions. The ZyXEL Device continues to delete half-open
requests as necessary, until the number of existing half-open sessions drops
below this number.
Maximum
Incomplete High
This is the number of existing half-open sessions that causes the firewall to
start deleting half-open sessions. When the number of existing half-open
sessions rises above this number, the ZyXEL Device deletes half-open sessions
as required to accommodate new connection requests. Do not set
Maximum
Incomplete High
to lower than the current
Maximum Incomplete
Low
number.
For example, if you set the maximum incomplete high to 100, the ZyXEL Device
starts deleting half-open sessions when the number of existing half-open
sessions rises above 100. It stops deleting half-open sessions when the number
of existing half-open sessions drops below the number set as the maximum
incomplete low.
TCP Maximum
Incomplete
An unusually high number of half-open sessions with the same destination host
address could indicate that a DoS attack is being launched against the host.
Specify the number of existing half-open TCP sessions with the same
destination host IP address that causes the firewall to start dropping half-open
sessions to that same destination host IP address. Enter a number between 1
and 256. As a general rule, you should choose a smaller number for a smaller
network, a slower system or limited bandwidth. The ZyXEL Device sends alerts
whenever the
TCP Maximum Incomplete
is exceeded.
Action taken when
TCP Maximum
Incomplete
reached threshold
Select the action that ZyXEL Device should take when the TCP maximum
incomplete threshold is reached. You can have the ZyXEL Device either:
Delete the oldest half open session when a new connection request comes.
or
Deny new connection requests for the number of minutes that you specify
(between 1 and 255).
Apply
Click this to save your changes.
Cancel
Click this to restore your previously saved settings.
Summary of Contents for P-660R-F1 series
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Page 8: ...Certifications P 660R F1 Series User s Guide 8 ...
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Page 18: ...P 660R F1 Series User s Guide 18 ...
Page 62: ...Chapter 4 WAN Setup P 660R F1 Series User s Guide 62 ...
Page 104: ...Chapter 7 Firewalls P 660R F1 Series User s Guide 104 ...
Page 140: ...Chapter 9 Certificates P 660R F1 Series User s Guide 140 ...
Page 144: ...Chapter 10 Static Route P 660R F1 Series User s Guide 144 ...
Page 162: ...Chapter 12 Dynamic DNS Setup P 660R F1 Series User s Guide 162 ...
Page 190: ...Chapter 15 System P 660R F1 Series User s Guide 190 ...
Page 204: ...Chapter 16 Logs P 660R F1 Series User s Guide 204 ...
Page 212: ...Chapter 18 Diagnostic P 660R F1 Series User s Guide 212 ...
Page 216: ...Chapter 19 Troubleshooting P 660R F1 Series User s Guide 216 ...
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