Wimax standards and Security The Wimax

FIGURE 8.11
Network scenario for Figure 8.10.

restriction that if a connection is assigned bandwidth with the centralized scheduling, its corresponding DI is in the DOWN state. This way all packets traversing the low QoS subnet will be transmitted on connections scheduled with the distributed scheduling protocol.

Figures 8.10 and 8.11 show how the logical interfaces and routing work together in practice. Figure 8.10 shows the routing table and the neighborhood table for node 2 in Figure 8.11. Each mesh node belongs to both the high and the low QoS subnets. The routing table associates the entire high QoS subnet with the CSI and it also associates each of the connections established with the node’s neighbors individually as peer-to-peer links in the low QoS subnet. When an IP packet arrives to an interface, the mesh ID of the final destination for the packet can be found by extracting the last 16 bits of the destination address. In the case of CSI, the next-hop link ID is found from the routing table of mesh IDs that CSI obtains from centralized scheduling messages. In the case of a DI, the link ID is obtained from the interface number associated with DI. The CID for the MAC layer data transmission can be obtained by combining the mesh ID of the node 2 with the link ID of the logical connection to the next-hop router.
The needs to notify the routing protocols when one of the connections
changes status from DOWN to UP-DSCH, or if the connection changes state from UP-DSCH to DOWN. We do not specify the exact notification method since it is operating system specific. For example, in the Linux operating system, it is sufficient to change the status of the logical MAC inter- face, which automatically updates the forwarding tables in the kernel [20]. The CS also needs to notify the network layer if all of the connections whose bandwidth was scheduled with the centralized scheduling protocol change state from UP-CSCH to DOWN. In this case, the CSI interface becomes unavailable since the node is disconnected from the centralized scheduling routing tree.

4.