Nortel 4524GT Configuration page 30

30 Chapter 1 An Introduction to Policy-Enabled Networks
At factory default, all ports are considered untrusted. However, for those
interface groups created, the default is unrestricted.
Because a port can belong to only one interface group, a port is classified
as trusted, untrusted, or unrestricted. These types are also referred to as
interface classes.
Trusted and untrusted ports are automatically associated with policies that
initiate default traffic processing. This default processing occurs if:
•
OR
•
The default processing of trusted and untrusted interfaces is as follows:
•
•
Copyright © 2007, Nortel Networks
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no actions are initiated based on user-defined policy criteria that
matches the traffic.
the actions associated with the user-defined policy do not conflict with
the default processing actions.
Trusted interfaces -- IPv4 traffic received on trusted interfaces is
re-marked at the layer 2 level, that is, the 802.1p user priority value is
updated based on the DSCP value in the packet at ingress and the
installed DSCP-to-CoS mapping data. The DSCP value is not updated.
Remapping occurs, by default, only for standardized DSCP values (for
example, EF, AFXX) and any proprietary Nortel values. The DSCP
values that are remapped are associated with a non-zero 802.1p user
priority value in the DSCP-to-COS Mapping Table.
Untrusted interfaces -- IPv4 traffic received on untrusted interfaces is
re-marked at the layer 3 level--that is, the DSCP value is updated. The
new DSCP value is determined differently depending on whether the
packet is untagged or tagged:
— Untagged frames
The DSCP value is derived using the default port priority of the
interface receiving the ingressing packet. This default port priority
is used to perform a lookup in the installed CoS-to-DSCP mapping
table.
The 802.1p user priority value is unchanged--that is, the default port
priority determines this value.
(Thus, the DSCP value on untagged frames on untrusted interfaces
is updated using the default port priority of the ingress interface; the
user sets the default port priority).
— Tagged frames
The DSCP value is re-marked to indicate best-effort treatment is
all that is required for this traffic.
Nortel Ethernet Routing Switch 4500 Series
Configuration — Quality of Service
NN47205-504 (322816-B)
5.1 23 November 2007
03.01 Standard