2 Problem statement
The basic scenario that we addressed consists of a Mobile Node that uses an Access Router to obtain connectivity to an operator’s network. However, the Access Router does not of-fer direct wireless connectivity to the Mobile Node; instead, it is connected to one or more Access Points, which provide the layer 2 connectivity to the Mobile Node.
A more complex scenario is characterized by concate-nated wireless links, as shown in Fig. 1. Here an IEEE 802.16 link (Base Station + Subscriber Station) is used to connect two Access Points in parallel: one 802.11 (Wireless LAN) and one IEEE 802.15.1 (Bluetooth). These scenarios are only examples; the ultimate topology addressed by the QoSAL is a generic L2 network composed of an arbitrary number of equipments interconnected to form a tree rooted at the Access Router.
The following goals were considered for the design of the QoSAL:
1. The main goal, to allow reservation of L2 QoS resources in wireless networks.
2. A flexible QoS model which adopts the common QoS models in the Internet: IntServ and DiffServ.
3. The parameters of the QoS model should be simple and generic, so that each Access Point can map them into its own technology.
4. Multiple concatenated wireless links should be sup-ported, and QoS should be reserved in all of them.
5. No a priori knowledge of the L2 network topology should be required by either Access Router or Mobile Node.
6. Dynamic changes in the L2 topology should be sup-ported.