International audienceTraceroute is widely used, from the diagnosis of network problems to the assemblage of internet maps. However, there are a few serious problems with this tool, in particu-lar due to the presence of load balancing routers in the net-work. This paper describes a number of anomalies that arise in nearly all traceroute-based measurements. We categorize them as "loops", "cycles", and "diamonds". We provide a new publicly-available traceroute, called Paris traceroute, which controls packet header contents to obtain a more pre-cise picture of the actual routes that packets follow. This new tool allows us to find conclusive explanations for some of the anomalies, and to suggest possible causes for others

Tools to measure internet properties usually assume the existence of a single path from a source to a destination. However, load-balancing capabilities, which create multiple active paths between two end-hosts, are available in most contemporary routers. This paper proposes a methodology to identify load-balancing routers and characterize loadbalanced paths. We enhance our traceroute-like tool, called Paris traceroute, to find all paths between a pair of hosts, and use it from 15 sources to over 68 thousand destinations. Our results show that the traditional concept of a single network path between hosts no longer holds. For instance, 39% of the source-destination pairs in our traces traverse a load balancer. Furthermore, this fraction increases to 70% if we consider the paths between a source and a destination network.

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