Chapter 4 Policy-enabled networks 289Using the Business Policy Switch 2000 Version 1.2• Interface groupsThe policies, by connecting these user-defined configurations, control the trafficon the switch.Ports are assigned to interface groups that are linked to policies. The policiesdetermine the traffic treatment of the flows.Packet flow using QoSUsing DiffServ and QoS, you can designate a specific performance level forpackets. This system allows you to prioritize network traffic. However, it requiressome thought to configure the prioritizations.You can specify a number ofpolicies, and each policy can match one or many flows—supporting complexclassification scenarios.This section contains a very simplified introduction to the many ways to prioritizepackets using QoS. In simple terms, the methods of prioritizing packets depend onthe DSCP and the 802.1 priority level and drop precedence.The QoS class basically directs which group of packets receives the best networkthroughput, which group of packets receives the next best throughput, and so on.The level of service for each packet is determined by the configurable DSCP.The available levels of QoS classes are currently named Premium, Platinum,Gold, Silver, Bronze, and Standard The level of service for each packet isdetermined by the configurable DSCP.Filters and filter groups basically sort the packets by various configurableparameters. These parameters include VLAN ID, IP source and subnet address, IPprotocol, and many others.The filter groups are associated with policies, and policies are organized into ahierarchy. The policy with the highest precedence is evaluated first. The filters andfilter groups are associated with interface groups, in that packets from a specificport will have the same filters as all others in the particular interface group (rolecombination).
