Nortel business policy switch 2000, Руководство пользователя

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304 Chapter 4 Policy-enabled networks
208700-C
Policy overview
When network traffic attributes match those specified in a traffic pattern, the
policy instructs the network device to perform a specified action on each packet
that passes through it.
Among policies, the policy with the lowest order (and highest precedence) is
evaluated first, then the policy with the next-lowest order and so on. For example,
with an order of 1 to 20, the system begins the evaluation with 1, moves onto 2,
and so forth. This is important to remember when you configure policies.
A policy is a network traffic-controlling mechanism that monitors the
characteristics of the traffic (for example, its source, destination, and protocol) and
performs a controlling action on the traffic when certain user-defined
characteristics are matched. A
policy action is the effect a policy has on network
traffic that matches the traffic profile of the policy.
The policies tie together:
• Actions
• Meters
• Shapers
• Filter groups
• Interface groups
Table 60 Shaping possibilities by class of interface
Action Trusted Untrusted Unrestricted
Shaping Traffic flow must be IP
or layer 2 packets
(matching IP) with a
specific DSCP value
Note: If a filter group
has multiple filters, all
filters must match the
identical DSCP value.
Yes • Traffic flow must be associated with policies that
have actions that update the 802.1p value at
egress.
• Traffic flow must be IP or layer 2 packets
(matching IP) with a specific DSCP value plus a
specified action of “useEgressMap.”
Note: If a filter group has multiple filters, all filters
must match the identical DSCP value