The impact of routing policy on internet paths

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.

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.

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-...

2003

BGP, the Border Gateway Protocol, is the de facto standard protocol for performing interdomain routing on the Internet today. Its main function is to distribute reachability information across the Internet, serving as the "glue" that holds the Internet together. BGP allows flexible configuration of routing policies from each local network and scalable operation, both at the cost of global visibility leading to complex and hard to predict dynamic behavior. BGP's dynamic behavior has so far received relatively little attention in the research community, due to ill-understood operational practices as well as insufficient resources to perform experiments. This thesis combines controlled active measurement in a testbed environment as well as on the actual Internet, correlating routing traffic with the forwarding plane and analyzing the protocol in detail using simulations to expose problems of interdomain routing dynamics. This class of problems may be difficult to reason statically due to the interaction of protocol components and can be observed more easily during run time. They include reachability, forwarding behavior, ix 5.9 Overall percentage of suppressed signals due route flap damping for each Beacon and on a per peer basis for Cisco and Juniper.. .. .. .. .. .. .. .. .. .. . 5.10 Percentage of suppressed Beacon signals due to announcement and withdrawal. . 5.11 The inter-arrival time distribution for each of the three Beacons as seen from Ciscolike and Juniper-like routers. The vertical dotted lines are drawn at 30 second intervals.113 5.12 The inter-arrival time distribution for Cisco-like last hop routers, and Beacon 1. . 5.

IEEE/ACM Transactions on Networking, 2008

Despite the architectural separation between intradomain and interdomain routing in the Internet, intradomain protocols do influence the path-selection process in the Border Gateway Protocol (BGP). When choosing between multiple equally-good BGP routes, a router selects the one with the closest egress point, based on the intradomain path cost. Under such hot-potato routing, an intradomain event can trigger BGP routing changes. To characterize the influence of hot-potato routing, we propose a technique for associating BGP routing changes with events visible in the intradomain protocol, and apply our algorithm to a tier-1 ISP backbone network. We show that (i) BGP updates can lag 60 seconds or more behind the intradomain event, (ii) the number of BGP path changes triggered by hot-potato routing has a nearly uniform distribution across destination prefixes, and (iii) the fraction of BGP messages triggered by intradomain changes varies significantly across time and router locations. We show that hot-potato routing changes lead to longer delays in forwarding-plane convergence, shifts in the flow of traffic to neighboring domains, extra externally-visible BGP update messages, and inaccuracies in Internet performance measurements. 1 To obtain up-to-date information about the size of routing tables, please reference http://www.cidr-report.org.

2004

In today's Internet core, routers store forwarding state proportional to the number of edge networks. As the Internet grows and core line rates increase, routers require memories that are increasingly fast and large-and are correspondingly increasingly expensive and difficult to engineer. In this paper, we present Reduced-State Routing (RSR), in which core routers require state only concerning the network topology within a two-hop radius, and thus of a size independent of the total number of Internet edge networks. RSR achieves this feat by routing geographically using two sets of node addresses: virtual coordinates, that are assigned to reflect the link costs within an autonomous system; and geographic coordinates, that correspond to nodes' physical locations. RSR routes greedily on virtual coordinates, and falls back to face routing on geographic coordinates when greedy progress is impossible on virtual coordinates. Unlike previous geographic routing schemes, RSR works on Internetlike graphs (rather than only on wireless-like graphs), and supports policy routing. By simulating RSR on real tier-1 ISP topologies, we demonstrate that RSR achieves low path stretch, comparable to that caused by policy routing in today's Internet.

IEEE Transactions on Dependable and Secure Computing, 2006

Several research studies have been devoted to improving the reliability and performance of the Internet by utilizing redundant communication paths between end points. Multihoming, coupled with intelligent route control, and overlay networks are two main streams in this area of research which attempt to leverage redundant connections of the Internet for increased reliability and performance. However, the effectiveness of these approaches depends on the natural diversity of redundant paths between two endhosts in terms of physical links, routing infrastructure, administrative control, and geographical distribution. Even in the case of redundant paths, if traffic between two hosts is not actually routed along completely disjoint paths, congestion or failure of a single shared link or router can adversely affect the end-to-end performance or availability of all paths. This paper presents an experimental study of path diversity on the Internet, focusing on the impact of path diversity on multihomed and overlay networks. We base our analysis on traceroutes and routing table data collected from several vantage points in the Internet including: looking glasses at 10 major Internet Service Providers (ISPs), RouteViews servers from 20 ISPs, and more than 50 PlanetLab nodes globally distributed across the Internet. Using this data, we quantify the extent of path diversity in multihoming and overlay networks, highlighting the limitations, and also identifying the source of the limitations in these architectures. From the analysis, we learn that both multihoming route control and current overlay networks are not able to ensure path diversity, which makes it very difficult to provide high-availability services even with the use of these systems. We believe that this work provides the insight into building future systems based on understanding path diversity.

Sigmetrics Performance Evaluation Review, 2004

Despite the architectural separation between intradomain and interdomain routing in the Internet, intradomain protocols do influence the path-selection process in the Border Gateway Protocol (BGP). When choosing between multiple equally-good BGP routes, a router selects the one with the closest egress point, based on the intradomain path cost. Under such hot-potato routing, an intradomain event can trigger BGP routing changes. To characterize the influence of hot-potato routing, we conduct controlled experiments with a commercial router. Then, we propose a technique for associating BGP routing changes with events visible in the intradomain protocol, and apply our algorithm to AT&T's backbone network. We show that (i) hot-potato routing can be a significant source of BGP updates, (ii) BGP updates can lag ¢ ¡ seconds or more behind the intradomain event, (iii) the number of BGP path changes triggered by hot-potato routing has a nearly uniform distribution across destination prefixes, and (iv) the fraction of BGP messages triggered by intradomain changes varies significantly across time and router locations. We show that hot-potato routing changes lead to longer delays in forwarding-plane convergence, shifts in the flow of traffic to neighboring domains, extra externally-visible BGP update messages, and inaccuracies in Internet performance measurements.

Physica A: Statistical Mechanics and its Applications, 2020

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2008

In this paper we examine how metrics impact route selection, looking at which metric(s) are selected and how these metrics are used to calculated cost. Examining multiple and dynamic metrics currently in use and looking toward a proposal of agent carrying dynamic metric information across an autonomous system.