Chapter4 Policy-enabled networks 283
Using the Business Policy Switch 2000 Version 1.2
The classifications of trusted, untrusted, and unrestricted actually apply to groups
of ports (interface groups). Because a port can belong to only one interface group,
a port will be classified as trusted, untrusted, or unrestricted. These types are also
referred to as interface classes. So, you have three classes of interface groups:
Trusted, untrusted, and unrestricted.
By default, all ports are untrusted. You must configure the ports to be trusted.
Table 5 7 shows the guidelines the switch uses to re-mark various fields based on
the type of traffic and class of interface group.
The Business Policy Switch does not trust the DSCP of IP traffic received from an
untrusted port, but it does trust the DSCP of IP traffic received from a trusted port.
Filters installed on trusted ports cannot change the DSCP of the IP packets
received on these ports. These filters specify an action that must change the IEEE
802.1p and drop precedence of the matching packets based on the incoming DSCP
using a table that matches each one of the 64 DSCP values to the corresponding
IEEE 802.1p priority. The values can be modifi ed by a policy server or by t he user .
Tabl e 57 Re-marking QoS fields by class of in terface group
Type of filter Action Trusted Untrusted Unrestricted
IP filter or
Layer 2 filter
matching IP
DSCP Cannot re-mark Must re-mark Re-mark or not
IEEE 802.1p Uses the DSCP to
802.1p table to mark Must re-mark Re-mark or not
Drop precedence Uses the DSCP to
802.1p table to mark Must re-mark Re-mark or not
Layer 2 filter
(non-IP) DSCP Cannot re-mark Cannot re-mark Cannot re-mark
IEEE 802.1p Cannot re-mark •Tagged—must re-mark
•Untagged—cannot
re-mark
Re-mark or not
Drop precedence Cannot re-mark •Tagged—must re-mark
•Untagged—cannot
re-mark
Re-mark or not