Issue No.02 - February (2008 vol.19)
Baochun Li , IEEE
Overlay networks are virtual networks residing overthe IP network, consequently, overlay links may share hiddenl ower-level bottlenecks. Previous work have assumed an independent overlay model: a graph with independent link capacities.We introduce a model of overlays which incorporates correlated link capacities and linear capacity constraints (LCC) to formulate hidden shared bottlenecks; we refer to these as LCC-overlays. We define metrics to qualitatively measure overlay quality in terms of its accuracy (in representing the true network topology) and efficiency (i.e., performance). Through analysis and simulations,we show that LCC-overlay is perfectly accurate and hence enjoys much higher efficiency than the inaccurate independent overlay. We discover that even a highly restricted LCC class — node basedLCC— yields near-optimal accuracy and significantly higher efficiency. We study two network flow problems in the context of LCC-graphs: Widest-Path and Maximum-Flow. Weprove that Widest-Path with LCC is NP-complete. We formulate Maximum-Flow with LCC as a linear program, and propose an efficient distributed algorithm to solve it. Based on the LCCmodel, we further study the problem of optimizing delay while still maintaining optimal or near-optimal bandwidth. We also outline a distributed algorithm to efficiently construct an overlay with node-based LCC.
Overlay networks, network protocols, algorithm/protocol design and analysis, network topology.
Ying Zhu, Baochun Li, "Overlay Networks with Linear Capacity Constraints", IEEE Transactions on Parallel & Distributed Systems, vol.19, no. 2, pp. 159-173, February 2008, doi:10.1109/TPDS.2007.70726