User`s guide

Defining Filters and Firewalls
Introduction to filters
6-2 Preliminary January 30, 1998 Pipeline User’s Guide
You can define conditions in filters to drop (reject) all packets except the ones
you explicitly allow, or allow all packets except the ones you explicitly drop.
Additionally, you can specify whether to apply the filter to inbound packets,
outbound packets, or all packets, regardless of their origin.
Depending on how a filter is used, it is either a data filter or a call filter. The
following describes each type:
• Data filter
Affects the flow of data. Packets are dropped (rejected) or forwarded
(accepted) as specified in the filter conditions. Mainly used for security.
• Call filter
Determines which packets can initiate a connection or reset the idle timer for
an established connection. Mainly used to prevent unnecessary connections.
Note:
Packets can pass through more than one filter. If both a data filter and call
filter are applied, the data filter takes precedence.
Data filters for dropping or forwarding certain packets
Data filters are commonly used for security, but they can be used for any purpose
that requires the Pipeline to drop or forward specific packets. For example, you
can use data filters to drop packets addressed to particular hosts, or to prevent
broadcasts from going across the WAN. You can also use data filters to allow
only specified devices to be accessed by users across the WAN.
Data filters do not affect the idle timer, and a data filter applied to a Connection
profile does not affect the answering process.
Figure 6-1. Data filters can drop or forward certain packets
WAN
Data Filter