Design , Implementation , and Evaluation of a Software - based Real - TimeEthernet

Distributed multimedia applications require performance guarantees from the underlying network subsystem. Ethernet has been the dominant local area network architecture in the last decade, and we believe that it will remain popular because of its cost-eeectiveness and the availability of higher-bandwidth Ethernets. We present the design, implementation and evaluation of a software-based timed-token protocol called RETHER that provides real-time performance guarantees to multimedia applications without requiring any modi-cations to existing Ethernet hardware. RETHER features a hybrid mode of operation to reduce the performance impact on non-real-time network traac, a race-condition-free distributed admission control mechanism, and an eecient token-passing scheme that protects the network against token loss due to node failures or otherwise. To our knowledge , this is the rst software implementation of a real-time protocol over existing Ethernet hardware. Performance measurements from experiments on a 10 Mbps Ethernet indicate that up to 60% of the raw bandwidth can be reserved without deteriorating the performance of non-real-time traac. Additional simulations for high bandwidth networks and faster workstation hardware indicate that the protocol allows reservation of a greater percentage of the available bandwidth. 1 Introduction With the growing trend towards distributed multimedia applications , it has become essential for the underlying systems to provide resource guarantees. Applications such as LAN-based teleconferencing and video-on-demand services require support for real-time data transport from the underlying network to support real-time video playback. LAN-based real-time transport also plays a critical role in extending WAN-based teleconferencing systems to the end-user's display, which may be connected to the site's WAN interface with a local area network. With the large existing base of Ethernets, it is essential to support such applications on the Ethernet. Our work addresses the problem of providing bandwidth guarantees on an Ethernet-based network.