Wimax standards and Security The Wimax

QoS-Aware Convergence Sublayer

The 802.16 standard specifies that the IP layer should be connected to the
802.16 MAC layer with a CS, which classifies packets to connections, based on their CID. The standard omits the details of how the CS should operate. In this section, we propose a CS that uses a combination of logical interfaces and QoS subnets to take advantage of 802.16 QoS in the network layer.
The CS is designed to work together with the 802.16 scheduler, since scheduling changes may affect QoS. For example, in centralized scheduling, a large number of connections may change their state at the same time. A large number of simultaneous changes in the entire topology would cause a wave of updates in a dynamic routing protocol such as OSPF [19]. While the routing tables are converging, data packets may bounce around the network, causing large delays. However, in decentralized scheduling, only a few con- nections change status at any given time. This is a normal operation of the MAC layer expected from dynamic routing protocols and consistent with the QoS provided by decentralized scheduling.
We address the QoS issues caused by changes in connection state with a QoS-aware convergence CS. The CS resides in the operating system of mesh routers (Figure 8.10). Our CS is a combination of logical interfaces provided to the network layer (IP) and the way the interfaces classify packets. There is one

_IP Network
layer
Routing Table Address Interface Link ID

Logical

csi rdi0 rdi1 rdi2 rdi3
10.1.0.0/16
10.2.0.1
10.2.0.2
Convergence ^10.2.0.3
csi rdi0 rdi1 rdi2
0.2.3
0
1
2

interfaces
sublayer
10.2.0.4
rdi3 3

Neighbor Table

	Mesh ID	Link ID
	0	0
MAC	2	1
layer	3	2
	4	3

802.16 MAC
^CID 0 1 2 3