Investigating Characteristics of Internet Paths

Abstract

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-to-end paths for routing anomalies, we observe that 4.4% of the path traces (involving 18% of the ASes) contain routing loops indicating misconfiguration of routers. Some of the ASes had over 100 routers involved in loops in path traces through their networks. We observe a much higher rate of anomalies in the AS level, with 45% of path traces containing an AS loop. Additionally, we discovered that few of the ASes bounce-back packets where some traces through their network traverse routers in both forward and backward directions. Determining path segments belonging to each AS, we further explore ingress to egress paths of ASes in addition to the source to destination paths within the AS. Analyzing trace segments between ingresses and egresses of an AS, we realized more than half of the ASes have the same router level path between any ingress-egress pair for the 2 months, but others implement load balancing. These results are different from earlier studies that indicated a high level of path dynamism. Our results indicate that the end-to-end path dynamism is due to the Border Gateway Protocol level rather than the router level within ASes.