Scalability of Wavelength Division Multiplexed Optical Passive Star Networks with Range Limited Tunable Transceivers

The number of stations attached to a single optical passive star is limited by current state of the art in optical technology. Also, the wavelength range of tunable optical transceivers is limited by current technology. Many high performance computing applications require the use of large size regular topologies for communication between computing nodes. Scalability of passive star networks built with these two limitations becomes an important issue for building larger networks. This is the subject of our study in this paper. In a previous related work we explored the design issues for networks built on a single passive star employing transceivers of a limited tuning range. Here we extend that study by considering the problem of connecting several optical passive stars, each embedded with a given virtual topology, to create larger aggregate networks. The design issues are analyzed and a number of design rules are proposed for building such aggregate networks. We study the scalability of embedded optical passive stars by considering the most commonly employed virtual topologies—complete graph, mesh and hypercube.     

Experiments with video transmission over an Asynchronous Transfer Mode (ATM) network

We present end-to-end performance of digital coded video (JPEG, MPEG-1, and MPEG-2) over a local asynchronuous transfer mode (ATM) network. We discuss performance in terms of both delay (jitter) and frame loss as a function of load. The experimental data reveal that the burstiness of the variable bit-rate-coded video streams degrades the performance significantly when the hosts and the network are stressed. Our results show that traffic smoothing decreases frame loss significantly while maintaining acceptable jitter and loss bounds. We also discuss requirements for system components, such as the network interface and switch, which are necessary to support video services efficiently.