An Experimental Study of Internet Path Diversity

Telecommunication Systems, 2013

Path Diversification is a new mechanism that can be used to select multiple paths between a given ingress and egress node pair using a quantified diversity measure to achieve maximum flow reliability. The path diversification mechanism is targeted at the end-to-end layer, but can be applied at any level for which a path discovery service is available. Path diversification also takes into account service requirements for low-latency or maximal reliability in selecting appropriate paths. Using this mechanism will allow future internetworking architectures to exploit naturally rich physical topologies to a far greater extent than is possible with shortest-path routing or equal-cost load balancing. We describe the path diversity metric and its application at various aggregation levels, and apply the path diversification process to 13 real-world network graphs as well as 4 synthetic topologies to asses the gain in flow reliability. Based on the analysis of flow reliability across a range of networks, we then extend our path diversity metric to create a compos-* Work performed while at The University of Kansas ite compensated total graph diversity metric that is representative of a particular topology's survivability with respect to distributed simultaneous link and node failures. We tune the accuracy of this metric having simulated the performance of each topology under a range of failure severities, and present the results. The topologies used are from nationalscale backbone networks with a variety of characteristics, which we characterize using standard graph-theoretic metrics. The end result is a compensated total graph diversity metric that accurately predicts the survivability of a given network topology.

ACM Transactions on Modeling and Performance Evaluation of Computing Systems

Interactive and multimedia applications depend on the stability of end-to-end paths for predictable performance and good quality of service. On the other hand, network providers depend on multiple paths to ensure fault tolerance and use load balancing between these paths to enhance the overall network throughput. In this study, we analyze path dynamics for both end-to-end paths and path segments within service providers’ networks using 2 months of measurement data from the RIPE Atlas platform, which collects path traces between a fixed set of source and destination pairs every 15 minutes. We observe that 78% of the end-to-end routes have at least two alternative Autonomous System (AS) paths with some end-to-end routes going through hundreds of different AS paths during the 2 months of analysis. While AS level paths are often prevalent for a day, there are considerable changes in the routing of the trace packets over the ASes for a longer duration of a month or longer. Analyzing end-...

Proceedings of the 2003 ACM SIGMETRICS international conference on Measurement and modeling of computer systems - SIGMETRICS '03, 2003

Measurement * Supported by Capes/Brazil 1 Note that layer-3 path diversity is distinct from physicallevel path diversity: several virtual links may share a physical link.

Routing policies used in the Internet can be restrictive, limiting communication between source-destination pairs to one path, when often better alternatives exist. To avoid route flapping, recovery mechanisms may be dampened, making adaptation slow. Unstructured overlays have been proposed to mitigate the issues of path and performance failures in the Internet by routing through an indirect-path via overlay peer(s). Choosing alternate-paths in overlay networks is a challenging issue. Ensuring both availability and performance guarantees on alternate paths requires aggressive monitoring of all overlay paths using active probing; this limits scalability. An alternate technique to select an overlay-path is to bias its selection based on physical disjointness criteria to bypass the failure on the primary-path. Recently, several techniques have emerged which can optimize the selection of a disjoint-path without incurring the high costs associated with probing paths. In this paper, we sh...

Proceedings of the 2007 ACM CoNEXT conference on - CoNEXT '07, 2007

Internet interdomain routing is policy-driven, and thus physical connectivity does not imply reachability. On average, routing on today's Internet works quite well, ensuring reachability for most networks and achieving reasonable performance across most paths. However, there is a serious lack of understanding of Internet routing resilience to significant but realistic failures such as those caused by the 911 event, the 2003 Northeast blackout, and the recent Taiwan earthquake in December 2006. In this paper, we systematically analyze how the current Internet routing system reacts to various types of failures by developing a realistic failure model, and then pinpoint reliability bottlenecks of the Internet. For validity of our simulation results, we generate topology graphs by addressing concerns over the incompleteness of topology and the inaccuracy of inferred AS relationships. By focusing on the impact of structural and policy properties, our analysis provides guidelines for future Internet design. The simulation tool we provide for analyzing routing resilience is also efficient to scale to Internet-size topologies.

Journal of Internet Services and Applications, 2011

We analyzed how reliability will be improved by adopting inter-domain multi-path and multi-homing routing when the structure in the Internet changes. We identified the properties of the ideal network structure that will maximize the advantage of multi-path and multi-home routing using mathematical analyses. We focused on how each end-to-end path is built, how many multi-paths exist and how each multi-path consists of multi-path and multi-homing segments. Second, we analyzed the trends in the recent changes in how the Internet is structured from the view point of inter-domain multi-path routing. The mathematical analyses suggest that a large number of multi-paths or multi-homing is not necessary to effectively benefit from multi-path routing. However, it will be important to keep the path length short in the segments where multiple paths are not available. The analyses on the recent changes in the Internet structure suggest that multi-path routing will contribute to improvement of re...

ACM SIGCOMM Computer Communication Review, 1999

The path taken by a packet traveling across the Internet depends on a large number of factors, including routing protocols and pernetwork routing policies. The impact of these factors on the endto-end performance experienced by users is poorly understood. In this paper, we conduct a measurement-based study comparing the performance seen using the "default" path taken in the Internet with the potential performance available using some alternate path. Our study uses five distinct datasets containing measurements of "path quality", such as round-trip time, loss rate, and bandwidth, taken between pairs of geographically diverse Internet hosts. We construct the set of potential alternate paths by composing these measurements to form new synthetic paths. We find that in 30-80% of the cases, there is an alternate path with significantly superior quality. We argue that the overall result is robust and we explore two hypotheses for explaining it.

2009

Today's Internet availability is low, despite the efforts of organizations to improve failure resilience through multi-homing. In this paper, we analyze where and how much exposure to topology is needed to best improve availability without sacrificing scalability. Through this analysis, we find that exposing choice of the first and last AS hops between multi-homed AS pairs can almost always provide a maximum number of AS disjoint paths through the network, whereas the paths exposed under multi-homing tend to share the same inbound route to multi-homed destinations. We qualify our topological analysis with an active measurement study showing that exposing choice of the first and last AS hops can provide availability approaching the optimal availability possible, suggesting that high availability can be obtained without sacrificing scalability.

Computer Communication Review, 1996

The large-scale behavior of routing in the Internet has gone virtually without any formal study, the exceptions being Chinoy's analysis of the dynamics of Internet routing information [Ch93], and recent work, similar in spirit, by Labovitz, Malan and Jahanian [LMJ97]. We report on an analysis of 40,000 end-to-end route measurements conducted using repeated "traceroutes" between 37 Internet sites. We analyze the routing behavior for pathological conditions, routing stability, and routing symmetry. For pathologies, we characterize the prevalence of routing loops, erroneous routing, infrastructure failures, and temporary outages. We find that the likelihood of encountering a major routing pathology more than doubled between the end of 1994 and the end of 1995, rising from 1.5% to 3.3%. For routing stability, we define two separate types of stability, "prevalence," meaning the overall likelihood that a particular route is encountered, and "persistence," the likelihood that a route remains unchanged over a long period of time. We find that Internet paths are heavily dominated by a single prevalent route, but that the time periods over which routes persist show wide variation, ranging from seconds up to days. About 2/3's of the Internet paths had routes persisting for either days or weeks. For routing symmetry, we look at the likelihood that a path through the Internet visits at least one different city in the two directions. At the end of 1995, this was the case half the time, and at least one different autonomous system was visited 30% of the time.

Lecture Notes in Computer Science, 2008

Path disruptions are frequent occurrences on today's Internet. They may be due to congestion or failures, which in turn may be attributed to unintentional factors (e.g., hardware failures) or caused by malicious activity. Several efforts to-date have focused on enhancing robustness from the end-to-end viewpoint by using path diversity. Most of these studies are limited to single-or two-path approaches. This paper is the first to address the question of what degree of path diversity is needed to effectively mitigate the effect of path failures. We seek to answer this question through extensive experiments in PlanetLab. To evaluate the effect of path diversity on routing robustness in regards to a wide spectrum of applications, we introduce a new performance metric we named outage duration. Experimental results show that proactively forwarding packets using a high degree of path diversity is more effective in overcoming path failures in comparison with single-path or two-path approaches. In addition, for applications in which low packet loss probability is as important as uninterrupted connectivity, we suggest a packet forwarding scheme based on link gains and discuss the trade-offs between robustness and packet delivery probability.