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SUMMARYThe system architecture of the Stony Brook Video Server (SBVS), which guarantees end-to-end real-time video playback in a client-server setting, is presented. SBVS employs a real-time network access protocol, RETHER, to use existing Ethernet hardware as the underlying communications media. The video server tightly integrates the bandwidth guarantee mechanisms for network transport and disk I/O. SBVS's stream-by-stream disk scheduling scheme optimizes the effective disk bandwidth without incurring significant scheduling overhead. To demonstrate the feasibility of the proposed architecture, we have implemented a prototype called SBVS-1, which can support five concurrent MPEG-1 video streams on an Intel 486DX2/EISA PC. To our knowledge, this system is the first video server that provides an end-to-end performance guarantee from the server's disks to the each user's display over standard Ethernet. This paper describes the implementation details of integrating network and I/O bandwidth guarantee mechanisms, and the performance measurements that drive and/or validate our design decisions.

With the advent of multimedia computing, there is an emerging need for systems that can support digital continuous media without requiring special adaptation logic on the part of application programs and that be implemented on existing network infrastructures. In this paper the system architecture of the Stony Brook Video Server (SBVS) is described. To guarantee real-time end-to-end performance, SBVS uses a real-time network access protocol, RETHER, that uses existing Ethernet hardware. SB VS tightly integrates the bandwidth guarantee mechanisms between network transport and disk I/O. SB VS's streamby-stream disk scheduling scheme optimizes the effective disk bandwidth without incurring scheduling overhead every cycle. In addition, SB VS implements multi-resolution video coding to reduce network and I/O bandwidth demands in normal viewing mode, while supporting fast forward/backward without requiring extra bandwidth. To demonstrate the feasibility of the proposed architecture, we have implemented the first prototype, SB VS-i, which can support five concurrent video streams on an EISA PC. To our knowledge, this is the first video server that provides an end-to-end performance guarantee from the server's disks to the each user's display over standard Ethernet. In this paper, we describe the implementation details of integrating network and I/O bandwidth guarantee mechanisms, and the performance measurements that drive and/or validate our design decisions.Keyword: video coding, multimedia file system, real-time performance guarantee, video-on-demand servers 1 Introduction Distributed multimedia computing introduces two new problems. First, very large aggregate I/O bandwidth is required and, second, real-time performance must be guaranteed. To successfully support multimedia, one needs to effectively address these two issues in almost every aspect of the computing system, including processors, networking, I/o, and system software. To support real-time data transfer, the Experimental Computer Systems group at Stony Brook has successfully developed and implemented a real-time network access protocol on top of existing Ethernet hardware. This network protocol, called RETHER, allows bandwidth reservation through admission control, and guarantees the allocated bandwidth to real-time connections without seriously penalizing non-real-time traffic. To provide end-to-end smooth digital video delivery from a server's I/O devices to each end user's display with real-time performance guarantees, we have embarked on the design and implementation of the Stony Brook Video Server (SB VS).