Using Process-Level Packet Routing to Support Real-Time Data Visualization: A Case Study in Antarctica

Minimizing latency and jitter is an important goal for communication in many distributed multimedia and visualization applications. This case study examines the impact of user-level packet routing on performance in a distributed system for controlling and monitoring the acquisition of geophysical data during aerial surveying in Antarctica. The packet routing mechanism employs concurrent processes and multiple display proxies communicating asynchronously via message passing and message queues. Asynchronous communication between processes reduces process blocking so that more data are available for realtime analysis. Performance tests indicate that proficient routing results in high packet throughput with low packet latency and jitter at multiple visualization stations during data acquisition. Our application routes packets of disparate sizes (73 12,386 bytes) at fixed rates (4 116 Hz). Performance metrics for individual packets (arrival times, travel intervals, drop times, drop intervals) reveal unexpected transfer anomalies. Large-sized packets show frequent periodic packet loss anomalies as packet transfer rates approach maximum system load. Intermittent losses of data stream synchrony due to small perturbations often result in large bursts of lost packets. These anomalies suggest that packet routing schemes operating near system capacity should be self-monitoring and possibly self-dampening when instabilities are detected. Keywords— packet routing, visualization, quality of service, data acquisition, performance, geophysics