Traceroute is largely considered as the number-one tool when troubleshooting the network, with innumerable applications, such as pinpointing the routing deficiencies or detecting and locating network outages. Previous works have extensively investigated pitfalls and flaws causing the measurements performed with this tool to be inaccurate or incomplete. In this paper, we show how, even in the absence of all these well-investigated pitfalls and flaws, our ability to properly troubleshoot the network with Traceroute is strongly limited. Indeed, by using state-of-the-art alias resolution techniques, we investigate how and how much the IP-level description provided by Traceroute can distort our understanding of the characteristics of Internet paths. We experimentally evaluate the impact on path properties like equal-cost multipaths, loops, routing cycles, load balancing, route prevalence and persistence. Our results confirm that researchers and network operators relying on Traceroute may poorly estimate (i) the number of multiple equal-cost routes to the destination; (ii) the presence of suboptimal routing in the network; (iii) the routing stability.

The dependence of the industry on cloud-based infrastructures has grown much faster than our understanding of the performance limits and dynamics of these environments. An aspect only marginally analyzed in the past is related to the performance of the intra-cloud network connecting the virtual machines (VMs) deployed in the same data center. The few available works either do not exhaustively describe the adopted methodology or employed different approaches causing the analyses to be hard to replicate, and the results to be hard to compare. In addition, cloud customers can today highly customize their cloud environments while previous works considered only a few of the scenarios in which a customer may operate. In this paper, we provide an intra-cloud network performance characterization of Microsoft (MS) Azure, a leading provider only preliminary investigated from this angle. We first propose and thoroughly detail a methodology to carry out similar analyses, thus encouraging its replication also in other contexts; then we apply this methodology to characterize the intra-cloud network performance in terms of maximum network throughput. More specifically, we investigate whether and how the achievable throughput between two VMs varies (i) over time; (ii) when the customer operates different decisions on VM size, network configuration, geographic region, and transport protocol; and (iii) when the customer operates the same decisions on these factors. Our analysis aims at addressing the gap existing in the literature by providing the most exhaustive and detailed results about the intra-cloud network performance for MS Azure today available.

Tracing Internet paths is essential for gathering knowledge about the complex, heterogeneous, highly dynamic, and largely opaque eco-system of networks the Internet is. Currently, only two practical solutions are available: (i) equipping packets with the Record Route IP option to register addresses of the traversed routers; (ii) eliciting ICMP Time Exceeded messages by limiting the Time-to-Live of the injected packets. In this paper, we investigate three alternative path tracing solutions eliciting ICMP Parameter Problem (PP) messages from the network through the injection of malformed packets. After having introduced them, we describe the experimental results of a first campaign aiming at evaluating their ability to collect replies from the traversed routers. Finally, thanks to a large-scale multi-vantage points measurement campaign, we evaluate the ability of the most promising ICMP PP-based solution to discover interfaces and routers not discovered by Paris-Traceroute Multipath Detection Algorithm (MDA). Experimental results (a) confirm the ability of this novel path tracing solution to report interfaces and routers that are not reported by the state of the art tools and also (b) uncover the scenarios in which this new solution appears more helpful.

Nowadays smart mobility, a new vision of urban mobility, is a reality. To implement smart mobility scenarios a deep integration among citizens, private and public transportation systems and ICT is required. With the S2-Move project we propose an architecture able to collect, update, and process real-time and heterogeneous information from various sources (tablets, smart-phones, probe vehicles) and actors of the urban scenario (public/private vehicles, pedestrians, infrastructures) in order to provide innovative mobility services. In this paper, we present a core component of the S2-Move project: the map-based web platform designed and implemented for providing smart mobility services. We present use cases and detail the design and the implementation of the platform. Finally, we evaluate the accuracy and efficiency of the Map Matching and Traffic Monitoring algorithms we implemented in our platform by using realistic urban traffic data generated through simulations in SUMO.

An accurate and exhaustive knowledge of the Internet topology is essential for a deep understanding of such a complex and ever-evolving ecosystem. In this context, a well-known key challenge is represented by alias resolution, i.e. the process of grouping under a unique identifier the addresses owned by the same network layer device. While several techniques exist, each solution shows specific limitations such that the alias resolution problem appears far from being definitively solved. In this work, inspired by a previous technique and the lessons learned by experimenting with IP options, we present, evaluate and release Pythia, a novel active probing-based alias resolution technique. Pythia exploits a combination of (i) UDP packet probes and (ii) the IP Prespecified Timestamp option and it is purposely designed to reconstruct a specific category of routers. By using the reliable topological information provided by IGMP probing as a reference, we experimentally evaluate Pythia and compare it to previously proposed techniques according to multiple performance metrics. Experimental results show how Pythia reaches higher performance in terms of applicability and trustworthiness.

Traceroute is probably the most famous networking tool widely adopted in both industry and research. Despite its long life, however, measurements based on Traceroute are potentially inaccurate, misleading or incomplete due to several unresolved issues. In this paper, we face the limitation represented by hidden routers-devices that do not decrement the TTL, being thus totally invisible to Traceroute. We present, evaluate and release DRAGO, a novel active probing technique composed of three main steps. First, a novel Traceroute enhanced by the IP Timestamp option is launched toward a destination. Second, a procedure is applied to quantify the hidden routers contained in the path, if any. Third, a last procedure is performed to identify the exact position in the path of the detected hidden routers. Experimental results demonstrate that the phenomenon is not uncommon: DRAGO detects the presence of hidden routers in at least 6% of the considered Traceroute IP paths and limits the affected area to one fifth of the trace containing these devices.

Recent developments in router level topology discovery have suggested the introduction of IGMP probing in addition to standard techniques such as traceroute and alias resolution. With a single IGMP probe, one can obtain all multicast interfaces and links of a multicast router. If such a probing is a promising approach, we noticed that IGMP probes are subject to filtering, leading so to the fragmentation of the collected multicast graph into several disjoint connected components. In this paper, we cope with the fragmentation issue. Our contributions are threefold: (i) we experimentally quantify the damages caused by IGMP filtering on collected topologies of large tier-1 ISPs; (ii) using traceroute data, we construct a hybrid graph and estimate how far each IGMP fragment is from each other; (iii) we provide and experimentally evaluate a recursive approach for reconnecting disjoint multicast components. The key idea of the third contribution is to recursively apply alias resolution to reassemble disjoint fragments and, thus, progressively extend the mapping of the targeted ISP. Data presented in the paper, as well as reconstructed topologies, are freely available at http://svnet.u-strasbg.fr/merlin.

Traceroute is probably the most famous computer networks diagnostic tool, widely adopted for both performance troubleshooting and research. Unfortunately, traceroute is not free of inaccuracies.

For a long time, traceroute measurements combined with alias resolution methods have been the sole way to collect Internet router level maps. Recently, a new approach has been introduced with the use of a multicast management tool, mrinfo, and a recursive probing scheme. In this paper, after analyzing advantages and drawbacks of probing approaches based on traceroute and mrinfo, we propose a hybrid discovery tool, Merlin (MEasure the Router Level of the INternet), mixing mrinfo and traceroute probes. Using a central server controlling a set of distributed vantage points in order to increase the exploration coverage while limiting the probing redundancy, the purpose of Merlin is to provide an accurate router level map inside a targeted Autonomous System (AS). Merlin also takes advantage of alias resolution methods to reconnect scattered multicast components. To evaluate the performance of Merlin, we report experimental results describing its efficiency in topology exploration and reconstruction of several ASes.