For upstream, the cable system is assumed to have a passband of 5-65 MHz. Analogue signals in 8 MHz channels may be present in addition to other signals. Protocol mechanisms through cable modem and CMTS described in this document are for both upstream and downstream traffic. 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.
The CMTS must enable or disable this capability on a per-modem basis with a tag length value in the registration response. 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. Concatenated protocol data units, and single ones as well, are encapsulated in the same manner. Baseline privacy, if enabled, is performed on each fragment, as opposed to the complete original MAC frame.