iers (CIDs) where each identifier permits a total of 64K connections within each downlink and uplink channel. The CID serves as a pointer to destination and context information even for connectionless traffic like IP. Each SS (subscriber station) or node in terms of the mesh network has a universal 48-bit MAC address as defined in the IEEE 802-2001 standard. It is used during the authentication process by which the network and SS (node) can verify each other. This address also serves as an equipment identifier, since the primary address used during operations are the CIDs. At SS initiation in the PMP configuration, three management connections are established between the SS and the BS (base station) each with its own level of QoS. The first of these is the basic connection that is used to exchange short, time-critical MAC management messages. The second primary management connection is used to exchange longer, more delay-tolerant MAC management messages such as those used for authentication. Finally, the secondary management connection is used for delay tolerant, standards-based messages such as Dynamic Host Configuration Protocol (DHCP), Trivial File Transfer Protocol (TFTP), Simple Network Management Protocol (SNMP), and SO on. In addition to these management connections, CIDs are also assigned for higher-layer sessions and contracted services. In terms of mesh network, the candidate nodes are identified via a 16-bit identifier (Node ID), which is transferred in the mesh sub-header. The sub-header follows the generic MAC header in both unicast and broadcast messages. On the other hand, nodes in the local neighborhood are identified with 8-bit link identifiers (Link IDs). The Link ID is transmitted as part of the CID in the generic MAC header in unicast messages. 4.2.1.3 MAC Security Sublayer The MAC Security sublayer provides authentication, secure key exchange, and encryption, which can be summed into "privacy" across the broadband wireless network. The privacy is achieved by encrypting connections between the