Frame based quality of service

A system and method for providing QoS levels to received data units, such as ATM cells and/or Frame Relay Frames. A QoS level associated with a virtual connection is supported through allocation and management of resources used to process data units received over the connection. Resources used to support QoS levels are assigned to groups of connections referred to as "QoS groups". Resources used to support one group of connections may be isolated from resources supporting other connections. When a connection is established, if a QoS group exists having the QoS level of the new connection, the connection may be added to that QoS group. Similarly, where the QoS levels for multiple connections must be modified, if those connections are within a single QoS group, then modification of the QoS level for that group would advantageously result in modification of the QoS for each virtual connection within the QoS group.