Chapter 10 Firewall
LTE7410 User’s Guide
75
Figure 55 Security > Firewall > Dos
The following table describes the labels in this screen.
10.5.1 The DoS Advanced Screen
For DoS attacks, the LTE Device uses thresholds to determine when to start dropping sessions that
do not become fully established (half-open sessions). These thresholds apply globally to all
sessions.
For TCP, half-open means that the session has not reached the established state-the TCP three-way
handshake has not yet been completed. Under normal circumstances, the application that initiates
a session sends a SYN (synchronize) packet to the receiving server. The receiver sends back an ACK
(acknowledgment) packet and its own SYN, and then the initiator responds with an ACK
(acknowledgment). After this handshake, a connection is established.
Figure 56 Three-Way Handshake
For UDP, half-open means that the firewall has detected no return traffic. An unusually high number
(or arrival rate) of half-open sessions could indicate a DOS attack.
10.5.1.1 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
Table 28 Security > Firewall > Dos
LABEL DESCRIPTION
Denial of Services Enable this to protect against DoS attacks. The LTE Device will drop sessions that surpass
maximum thresholds.
Apply Click this to save your changes.
Cancel Click this to restore your previously saved settings.
Advanced Click this to go to a screen to specify maximum thresholds at which the LTE Device will
start dropping sessions.
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