Alcatel Speed Touch Wireless, User Manual

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13 Networking Services - Firewalling
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3EC 17766 AAAA TCZZA Ed. 01
13.1 Operation of the Firewall
The STWireless Firewall is a set of related programs that protects
the resources of your local network from users from other
networks.
Basically, a firewall examines each network packet to determine
whether to forward it toward its destination. Firewalls work in most
cases closely together with a proxy server that makes network
requests on behalf of your local network users.
For the
STWireless Firewall the STWireless acts as well as
network gateway and proxy server to contact the outside world via
the ADSL line
The
STWireless Firewall is in fact a packet filter: inside and
outside nodes are visible to each other at the IP level, but the
firewall filters out, i.e. blocks the passage of certain packets,
based on their header.
Packets are intercepted at certain Packet Interception Point (PIP),
called , in the STWireless IP router. At this points, they are
matched against a chain, which comprises rules (at least one).
These rules determine the type of control implemented on the
packets.
Incoming and outgoing traffic is validated by comparing certain
values in the packets with configured Firewall parameters. The
parameters in a rule can be divided according to the protocol to
which they belong: a first group validates traffic on the interface
level, a second group on IP level, a third group filters on TCP, UDP,
and ICMP level.