Wimax standards and Security The Wimax

FIGURE 8.10
Routing and neighbor tables in a 802.16 router. The routing table resides in the network layer and it associates network addresses to interfaces. For the DCI, the routing table associates the entire high QoS subnet range with the interface. For normal interfaces, the routing table associates individual neighbor IP addresses with the interface. The neighbor link table resides in the MAC layer and it matches mesh IDs to links. Mesh IDs are obtained from the last 16 bits of the IP address.
logical interface for all packets traversing the centralized scheduling routing tree (centralized scheduling interface [CSI]) and multiple logical interfaces for each data connection on the router (data interfaces [DIs]).
The idea behind having a special interface for all connections using central- ized scheduling is to hide the routing taking place in the MAC layer from the network layer. The routing table assigns the high-quality QoS subnet to the CSI, so that packets traversing the high QoS subnet are forwarded through the CSI. When a packet comes to CSI, the interface finds out the mesh ID of destination from the IP destination address and forwards the packet on the logical connection that is the next hop in the centralized scheduling tree. The CSI interface presents the network layer with static routes along the central- ized scheduling routing tree, even though the actual routes may change if the link schedule changes. In effect, the CSI interface performs bridging for the high QoS traffic in the network.
Data interfaces have a one-to-one correspondance with the 802.16 connec- tions. When an IP packet is forwarded to a DI, it is transmitted to the mesh router linked with the corresponding logical connection, so DIs are assigned peer addresses corresponding to their 802.16 peers. Since, some of the con- nections may have their bandwidth assigned with the centralized scheduling and others may have bandwidth assigned with decentralized scheduling, there are no guarantees on how the DI bandwidth is assigned. However, if connections are restricted from being in the UP-ALL state, no connection will be assigned both centralized and decentralized bandwidths. We also add a

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Mesh ID: 1

Mesh ID: 2 Mesh ID: 4

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