User`s guide

Chapter 9 Firewalls
P-660HN-Fx User’s Guide
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Figure 89 Security > Firewall > Rules: Edit: Edit Customized Services: Config
The following table describes the labels in this screen.
9.4 The Firewall Threshold Screen
For DoS attacks, the ZyXEL 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.
Table 56 Security > Firewall > Rules: Edit: Edit Customized Services: Config
LABEL DESCRIPTION
Config
Service Name Type a unique name for your custom port.
Service Type Choose the IP port (TCP, UDP or TCP/UDP) that defines your customized port from
the drop down list box.
Port Configuration
Type Click Single to specify one port only or Range to specify a span of ports that define
your customized service.
Port Number Type a single port number or the range of port numbers that define your customized
service.
Back Click this to return to the previous screen without saving.
Apply Click this to save your changes.
Cancel Click this to restore your previously saved settings.
Delete Click this to delete the current rule.