They include packet classification and flow identification, service flow QoS scheduling, dynamic service establishment, fragmentation and the two-phase activation model. Protocol mechanisms through cable modem and CMTS described in this document are for both upstream and downstream traffic. The principle mechanism for providing enhanced QoS is to classify packets traversing the RF MAC interface into a service flow. The cable modem and CMTS provide this QoS by shaping, policing and prioritizing traffic according to the QoS parameter set defined for the service flow. The prime objective of QoS is to define transmission ordering and scheduling on the RF interface.
Fragmentation is an upstream cable modem capability.
When enabled for a service flow, fragmentation is initiated by the CMTS when it grants bandwidth to a particular modem. The grant size must be smaller than the corresponding bandwidth request from the modem. Baseline privacy, if enabled, is performed on each fragment, as opposed to the complete original MAC frame. Similar rules apply to the differential fiber-optical or electrical spacing. For the downstream frequency plan the cable is assumed to have a passband with a lower edge at 96 MHz and an upper edge that typically is between 300 and 864 MHz.