ZyXEL Communications PMG5318-B20A User Manual page 129

Chapter 15 Firewall
Anti-Probing
If an outside user attempts to probe an unsupported port on your GPON Device, an ICMP response
packet is automatically returned. This allows the outside user to know the GPON Device exists. The
GPON Device supports anti-probing, which prevents the ICMP response packet from being sent.
This keeps outsiders from discovering your GPON Device when unsupported ports are probed.
ICMP
Internet Control Message Protocol (ICMP) is a message control and error-reporting protocol
between a host server and a gateway to the Internet. ICMP uses Internet Protocol (IP) datagrams,
but the messages are processed by the TCP/IP software and directly apparent to the application
user.
DoS Thresholds
For DoS attacks, the GPON Device uses thresholds to determine when to drop sessions that do not
become fully established. These thresholds apply globally to all sessions. You can use the default
threshold values, or you can change them to values more suitable to your security requirements.
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PMG5318-B20A User's Guide