xample configuration per user: Max. bandwidth N X 4.5 Mbit/s 1) Up to 3 IPTV receivers: DL min. bandwidth 3 X 3Mbit/s DL max. bandwidth 3 X 4.5 Mbit/s UL: < 3 X 100 kbit/s 2) Up to 2 VolP endpoints: 2 X 100 kbit/s DL 2 X 100 kbit/s UL M VolP flows: 3) Internet access: M X 100 kbit/s DL: from 10.3 to 24 Mbit/s UL: from 2.5 to 3 Mbit/s Customer network Internet traffic Ethernet node router DSLAM aggregation AAA - Authentication, authorization and accounting ADSL - Asymmetric digital subscriber line BRAS - Broadband remote access server DL - Downlink DSLAM - Digital subscriber line access multiplexer UL - Uplink Figure 4.4 Use of priority and scheduling for QoS provisioning in a DSL network. Hierarchical scheduling (HS). It must be supported on BRAS gateways. In that manner, to preserve IP QoS downstream toward customer premises, it uses packet classification, traffic shaping (which limits the peaks in the bitrate from the bursty traffic such as video or the Web), and hierarchical scheduling that is implemented as a logical tree-based network between the BRAS and the residential (i.e. home) gateways. While for ATM there are five levels of hierarchy (corresponding to session, VC, group of VCs, virtual path, and port), in Ethernet-based DSL there is a minimum of three levels of hierarchy (BRAS or broadband network gateway port, access node uplink, and synch rate between the network and residential/home gateways in the access local loop). 4.3.2 QoS for Cable Access The DOCSIS standards 3.0 and 3.1 define a set of QoS mechanisms on MAC and upper layer protocols based on a fundamental network resource management con- struct: service flow. Service flow is defined as a MAC-layer transport service which is created to provide unidirectional transport of packets from the upper layer service entity to the physical layer of the cable (the RF), as well as to shape, police, and prioritize traffic according to a set of QoS traffic parameters defined for the given flow [16]. As typical for all fixed access networks with a shared me