Stefan Savage

California Fault Lines: Understanding the Causes and Impact of Network Failures

Daniel Turner, Kirill Levchenko, Alex C. Snoeren, and Stefan Savage
Appears in: 
CCR October 2010

Of the major factors affecting end-to-end service availability, network component failure is perhaps the least well understood. How often do failures occur, how long do they last, what are their causes, and how do they impact customers? Traditionally, answering questions such as these has required dedicated (and often expensive) instrumentation broadly deployed across a network.

XL: An Efficient Network Routing Algorithm

Kirill Levchenko, Geoffrey M. Voelker, Ramamohan Paturi, and Stefan Savage
Appears in: 
CCR October 2008

In this paper, we present a new link-state routing algorithm called Approximate Link state (XL) aimed at increasing routing efficiency by suppressing updates from parts of the network. We prove that three simple criteria for update propagation are sufficient to guarantee soundness, completeness and bounded optimality for any such algorithm. We show, via simulation, that XL significantly outperforms standard link-state and distance vector algorithms—in some cases reducing overhead by more than an order of magnitude— while having negligible impact on path length.

Automating Cross-Layer Diagnosis of Enterprise Wireless Networks

Yu-Chung Cheng, Mikhail Afanasyev, Patrick Verkaik, Péter Benkö, Jennifer Chiang, Alex C. Snoeren, Stefan Savage, and Geoffrey M. Voelker
Appears in: 
CCR October 2007

Modern enterprise networks are of sufficient complexity that even simple faults can be difficult to diagnose — let alone transient outages or service degradations. Nowhere is this problem more apparent than in the 802.11-based wireless access networks now ubiquitous in the enterprise. In addition to the myriad complexities of the wired network, wireless networks face the additional challenges of shared spectrum, user mobility and authentication management.

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