User`s guide

Filters
5-3
Detailed examples of filter applications are presented later in this
chapter. (See Filtering Application Examples.)
5.3 USING FILTERS TO IMPROVE PERFORMANCE
In many applications, ATX filters can be used to enhance network
performance by preventing certain types of traffic which may
degrade performance. A filter that defines logical barriers to
protect a network segment or segments from conditions that may
degrade network performance is referred to as a firewall filter.
Firewalls define logical barriers to protect a network segment or
segments from conditions that may degrade network performance.
Examples of degrading conditions that may be controlled by
firewall filters include unnecessary traffic, broadcast storms, and
conflicting applications that occur within a particular segment.
Firewall filters can also be used to help implement fault isolation,
error recovery, and security measures.
A firewall filter may be an address table filter or a combination
port filter. Three examples of firewall applications are described
below. Firewall filters can be configured to:
• Allow server traffic only to be forwarded from LAN A to LANs
B and C. (Other traffic would not be forwarded.)
• Prevent a specific type of traffic from being forwarded to a
specific network segment. (For example, it might be desirable to
block DECnet broadcast traffic from a LAN that includes no
devices that use DECnet data packets. This would be an
example of blocking unnecessary traffic.)
• Prevent multicast packets from being forwarded to a specific
network segment (localized broadcast storm prevention).
An example of a firewall filter is given in the section, Filtering
Application Examples.
Note: The ATX multicast storm protection feature may be thought of as
a firewall feature, in that it performs a protective blocking function,