Stretching gossip with live streaming

Gossip-based information dissemination protocols are considered easy to deploy, scalable and resilient to network dynamics. They are also considered highly flexible, namely tunable at will to increase their robustness and adapt to churn. So far however, they have mainly been evaluated through simulation, very often assuming ideal settings. Instead, in this paper, we report on an extensive study of gossip protocols, deployed on a 230 Planetlab node testbed, in the context of a challenging video streaming application in environments with constrained bandwidths. More precisely, we assess the impact of varying the well known knobs of gossip, fanout and refresh rate, in various upload-bandwidth distributions and churn. Our results show that in such challenging contexts, the performance of gossip protocols may be hampered by high fanout values. We also show that the more proactive a gossip protocol, the better it copes with churn. For instance, when 20% of the nodes simultaneously crash, 70% of the remaining nodes do not suffer any loss in stream quality, while the others only experience a performance decrease for an average of 5 seconds around the churn event.