Nortel BCM 3.7, Manual

Page: 800 / 1004

800 Policy configuration overview
N0008589 3.3
COPS
When used with the Optivity Policy Services ® (OPS) Version 1.2 or later, a comprehensive
network management application combining IP address management with policy-based network
traffic control, Business Communications Manager effectively manages network traffic and
resources. Information is transferred using the Common Open Policy Services (COPS) protocol, a
query and response protocol that exchanges policy information messages using the Transmission
Control Protocol (TCP). Specifically, COPS for Provisioning (COPS-PR) is used to download
information. COPS is used to communicate with edge devices on the network.
OPS provides a centralized management point for DiffServ policies. The policy server distributes
policies to edge devices and border routers. These edge devices police traffic flows by marking
packets and applying forwarding behaviors to the packets at the network node.
For further information about Optivity products, contact your Nortel Networks sales
representative.
Policy overview
Use Unified Manager to configure policies and filters to control the behavior of network traffic. 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. You can assign only one action to a
policy. You set up
filters to establish packet-specific criteria that determine how a packet is to be
processed. You can use filters to remark packets by updating the DSCP code points, to change
priorities, or to drop packets.
LAN ports on Business Communications Manager are configured according to the policy
determining traffic priorities. As packets enter the switch, they are marked according to their
priority.
After the packets are marked, they are moved to the proper egress queue based on their marking.
When a packet is to be transmitted, the switch looks at the Premium queue first. Then Business
Communications Manager examines the other queues and sends packets based on the weighted
percentage for the queues. The entire process is repeated. This approach ensures that the Premium
packets are serviced quickly and that the other data types (other queues) are not starved and
serviced in a round-robin fashion.
A packet is processed as follows:
1 The packet enters Business Communications Manager.
2 Filters are applied.
3 Filter actions are taken and the packet can be modified (DSCP).
4 The packet is assigned a QoS class. A QoS class is designated using the DSCP values.
5
The packet is placed in the appropriate egress queue according to its priority marking as
described above.
6 The queues are serviced in a round-robin fashion (strict priority or weighted fair queueing).