Arcadyan FXT-850W, Руководство пользователя

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Data
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Web Management
Stateful Packet
Inspection This option allows you to select different
application types that are using dynamic
port numbers. If you wish to use Stateful
Packet Inspection (SPI) for blocking
packets, click on the Yes radio button in the
“Enable SPI and Anti-DoS firewall
protection” field and then check the
inspection type that you need, such as
Packet Fragmentation, TCP Connection,
UDP Session, FTP Service, H.323 Service,
and TFTP Service.
It is called a “stateful” packet inspection
because it examines the contents of the
packet to determine the state of the
communication; i.e., it ensures that the
stated destination computer has previously
requested the current communication. This
is a way of ensuring that all
communications are initiated by the
recipient computer and are taking place
only with sources that are known and
trusted from previous interactions. In
addition to being more rigorous in their
inspection of packets, stateful inspection
firewalls also close off ports until a
connection to the specific port is requested.
When particular types of traffic are
checked, only the particular type of traffic
initiated from the internal LAN will be
allowed. For example, if the user only
checks FTP Service in the Stateful Packet
Inspection section, all incoming traffic will
be blocked except for FTP connections
initiated from the local LAN.
Parameter Defaults Description