Implementation Experiences of Bandwidth Guarantee on a Wireless LAN

The Rether[1] protocol was originally developed to support guaranteed Quality of Service (QoS) for shared Ethernet LANs. In view of the growing popularity of IEEE 802.11-based wireless LANs, we have modified the Rether protocol to provide QoS guarantee on these networks. In this paper, we present the design and software-only implementation of the Wireless Rether protocol for 802.11 networks, as well as our experiences with wireless LAN hardware. Wireless Rether supports QoS for TCP and UDP traffic in both upstream and downstream directions. The protocol can seamlessly inter-operate with any priority-based QoS mechanisms (such as Diffserv [6]) on the wired networks that connect the wireless access network to the rest of the Internet. The QoS requirements of real-time applications are specified as a simple configurable policy. Legacy networking applications can benefit from QoS guarantees provided by Wireless Rether without requiring any modifications. In addition to QoS guarantee, Wireless Rether provides a novel low-latency handoff mechanism for Mobile IP connections over infrastructure-mode wireless LANs.