dwidth granting mechanism (continuous or on-demand) Associated QoS parameters Routing and transport data. Connections are typically unidirectional, SO that different QoS and other transport parameters can be defined for the uplink and downlink directions. When a new subscriber station joins an 802.16 network, three connections are initially opened to carry management level messages, as shown in Table 12-6. Table 12-6: 802.16 SS Management Connections Connection Usage Basic management connection Short, time-critical MAC and radio link control (RLC) messages. Primary management connection Delay tolerant messages e.g. authentication, connection set-up. Secondary management Standards based management messaging; connection DHCP, SNMP, RIP. Wireless MAN Standards Additional connections are allocated to subscribers when specific services are contracted, typically in uplink plus downlink pairs. The MAC also reserves a number of connections for other general purposes, such as initial contention-based access and broadcast or multicast transmissions, including polling of SS bandwidth needs. Radio Link Control Radio link control (RLC) is another key element of the 802.16 MAC that is required to provide adaptive burst control as well as the more traditional power adjustment functions (TPC). When a subscriber joins the network, SS and BS exchange messages using the basic management connection to establish initial settings for transmit power and timing. The SS will also request a specific initial burst profile, defining signal modulation parameters, based on equipment capabilities and downlink signal quality. The RLC will continue to monitor signal quality after this initial set-up, and either the SS or BS may request a more robust burst profile if environmental conditions deteriorate (e.g. temporarily switching from 64-QAM to 16-QAM) or a more efficient profile if lower robustness can be tolerated as conditions improve. The uplink burst profile is under the direct control of the BS, and this control is achieved each time the B