Port groups allow the user to define ports by similar functionality or role. The user can create port groups and use them to configure QoS profiles, ingress meters and flood rate-limiters for ports that share the same role. In addition, Extreme Management Center will create and manipulate port groups through the CoS (Class of Service) MIB via SNMP. These groups will be used to configure the Extreme Management Center-specified CoS resources that are mapped to QoS profiles, ingress meters and flood rate-limiters. Since the Extreme Management Center CoS feature is port group- oriented, extremeXOS QoS entities (e.g. QoS profiles, ingress meter, and flood rate-limiting) that are configured on a per-port basis are not exposed through the CoS MIB via SNMP.