Improving the discovery of IXP peering links through passive BGP measurements

The Internet Autonomous System (AS) topology has important implications on end-to-end routing, network economics and security. Despite the significance of the AS topology research, it has not been possible to collect a complete map of the AS interconnections due to the difficulties involved in discovering peering links. The problem of topology incompleteness is amplified by the increasing popularity of Internet eXchange Points (IXPs) and the 'flattening' AS hierarchy. A recent study discovered that the number of missing peering links at a single IXP is larger than the total number of the observable peering links. As a result a large body of research focuses on measurement techniques that can alleviate the incompleteness problem. Most of these proposals require the deployment of additional BGP vantage points and traceroute monitors. In this paper we propose a new measurement methodology for improving the discovery of missing peering links through the publicly available BGP data. Our approach utilizes the traffic engineering BGP Communities used by IXPs' Route Servers to implement multi-lateral peering agreements. We are able to discover 36K additional p2p links from 11 large IXPs. The discovered links are not only invisible in previous BGP-based AS topology collections, but also 97% of those links are invisible to traceroute data from CAIDA's Ark and DIMES projects for June 2012. The advantages of the proposed technique are threefold. First, it provides a new source of previously invisible p2p links. Second, it does not require changes in the existing measurement infrastructure. Finally, it offers a new source of policy data regarding multilateral peering links at IXPs

Inferring multilateral peering

The AS topology incompleteness problem is derived from difficulties in the discovery of p2p links, and is amplified by the increasing popularity of Internet eXchange Points (IXPs) to support peering interconnection. We describe, implement, and validate a method for discovering currently invisible IXP peering links by mining BGP communities used by IXP route servers to implement multilateral peering (MLP), including communities that signal the intent to restrict announcements to a subset of participants at a given IXP. Using route server data juxtaposed with a mapping of BGP community values, we can infer 206K p2p links from 13 large European IXPs, four times more p2p links than what is directly observable in public BGP data. The advantages of the proposed technique are threefold. First, it utilizes existing BGP data sources and does not require the deployment of additional vantage points nor the acquisition of private data. Second, it requires only a few active queries, facilitating repeatability of the measurements. Finally, it offers a new source of data regarding the dense establishment of MLP at IXPs

Methods for revealing and reshaping the African Internet Ecosystem as a case study for developing regions: from isolated networks to a connected continent

Mención Internacional en el título de doctorWhile connecting end-users worldwide, the Internet increasingly promotes local development by making challenges much simpler to overcome, regardless of the field in which it is used: governance, economy, education, health, etc. However, African Network Information Centre (AfriNIC), the Regional Internet Registry (RIR) of Africa, is characterized by the lowest Internet penetration: 28.6% as of March 2017 compared to an average of 49.7% worldwide according to the International Telecommunication Union (ITU) estimates [139]. Moreover, end-users experience a poor Quality of Service (QoS) provided at high costs. It is thus of interest to enlarge the Internet footprint in such under-connected regions and determine where the situation can be improved. Along these lines, this doctoral thesis thoroughly inspects, using both active and passive data analysis, the critical aspects of the African Internet ecosystem and outlines the milestones of a methodology that could be adopted for achieving similar purposes in other developing regions. The thesis first presents our efforts to help build measurements infrastructures for alleviating the shortage of a diversified range of Vantage Points (VPs) in the region, as we cannot improve what we can not measure. It then unveils our timely and longitudinal inspection of the African interdomain routing using the enhanced RIPE Atlas measurements infrastructure for filling the lack of knowledge of both IPv4 and IPv6 topologies interconnecting local Internet Service Providers (ISPs). It notably proposes reproducible data analysis techniques suitable for the treatment of any set of similar measurements to infer the behavior of ISPs in the region. The results show a large variety of transit habits, which depend on socio-economic factors such as the language, the currency area, or the geographic location of the country in which the ISP operates. They indicate the prevailing dominance of ISPs based outside Africa for the provision of intracontinental paths, but also shed light on the efforts of stakeholders for traffic localization. Next, the thesis investigates the causes and impacts of congestion in the African IXP substrate, as the prevalence of this endemic phenomenon in local Internet markets may hinder their growth. Towards this end, Ark monitors were deployed at six strategically selected local Internet eXchange Points (IXPs) and used for collecting Time-Sequence Latency Probes (TSLP) measurements during a whole year. The analysis of these datasets reveals no evidence of widespread congestion: only 2.2% of the monitored links experienced noticeable indication of congestion, thus promoting peering. The causes of these events were identified during IXP operator interviews, showing how essential collaboration with stakeholders is to understanding the causes of performance degradations. As part of the Internet Society (ISOC) strategy to allow the Internet community to profile the IXPs of a particular region and monitor their evolution, a route-collector data analyzer was then developed and afterward, it was deployed and tested in AfriNIC. This open source web platform titled the “African” Route-collectors Data Analyzer (ARDA) provides metrics, which picture in real-time the status of interconnection at different levels, using public routing information available at local route-collectors with a peering viewpoint of the Internet. The results highlight that a small proportion of Autonomous System Numbers (ASNs) assigned by AfriNIC (17 %) are peering in the region, a fraction that remained static from April to September 2017 despite the significant growth of IXPs in some countries. They show how ARDA can help detect the impact of a policy on the IXP substrate and help ISPs worldwide identify new interconnection opportunities in Africa, the targeted region. Since broadening the underlying network is not useful without appropriately provisioned services to exploit it, the thesis then delves into the availability and utilization of the web infrastructure serving the continent. Towards this end, a comprehensive measurement methodology is applied to collect data from various sources. A focus on Google reveals that its content infrastructure in Africa is, indeed, expanding; nevertheless, much of its web content is still served from the United States (US) and Europe, although being the most popular content source in many African countries. Further, the same analysis is repeated across top global and regional websites, showing that even top African websites prefer to host their content abroad. Following that, the primary bottlenecks faced by Content Providers (CPs) in the region such as the lack of peering between the networks hosting our probes and poorly configured DNS resolvers are explored to outline proposals for further ISP and CP deployments. Considering the above, an option to enrich connectivity and incentivize CPs to establish a presence in the region is to interconnect ISPs present at isolated IXPs by creating a distributed IXP layout spanning the continent. In this respect, the thesis finally provides a four-step interconnection scheme, which parameterizes socio-economic, geographical, and political factors using public datasets. It demonstrates that this constrained solution doubles the percentage of continental intra-African paths, reduces their length, and drastically decreases the median of their Round Trip Times (RTTs) as well as RTTs to ASes hosting the top 10 global and top 10 regional Alexa websites. We hope that quantitatively demonstrating the benefits of this framework will incentivize ISPs to intensify peering and CPs to increase their presence, for enabling fast, affordable, and available access at the Internet frontier.Programa Oficial de Doctorado en Ingeniería TelemáticaPresidente: David Fernández Cambronero.- Secretario: Alberto García Martínez.- Vocal: Cristel Pelsse

From the edge to the core : towards informed vantage point selection for internet measurement studies

Since the early days of the Internet, measurement scientists are trying to keep up with the fast-paced development of the Internet. As the Internet grew organically over time and without build-in measurability, this process requires many workarounds and due diligence. As a result, every measurement study is only as good as the data it relies on. Moreover, data quality is relative to the research question—a data set suitable to analyze one problem may be insufficient for another. This is entirely expected as the Internet is decentralized, i.e., there is no single observation point from which we can assess the complete state of the Internet. Because of that, every measurement study needs specifically selected vantage points, which fit the research question. In this thesis, we present three different vantage points across the Internet topology— from the edge to the Internet core. We discuss their specific features, suitability for different kinds of research questions, and how to work with the corresponding data. The data sets obtained at the presented vantage points allow us to conduct three different measurement studies and shed light on the following aspects: (a) The prevalence of IP source address spoofing at a large European Internet Exchange Point (IXP), (b) the propagation distance of BGP communities, an optional transitive BGP attribute used for traffic engineering, and (c) the impact of the global COVID-19 pandemic on Internet usage behavior at a large Internet Service Provider (ISP) and three IXPs.Seit den frühen Tagen des Internets versuchen Forscher im Bereich Internet Measu- rement, mit der rasanten Entwicklung des des Internets Schritt zu halten. Da das Internet im Laufe der Zeit organisch gewachsen ist und nicht mit Blick auf Messbar- keit entwickelt wurde, erfordert dieser Prozess eine Meg Workarounds und Sorgfalt. Jede Measurement Studie ist nur so gut wie die Daten, auf die sie sich stützt. Und Datenqualität ist relativ zur Forschungsfrage - ein Datensatz, der für die Analyse eines Problems geeiget ist, kann für ein anderes unzureichend sein. Dies ist durchaus zu erwarten, da das Internet dezentralisiert ist, d. h. es gibt keinen einzigen Be- obachtungspunkt, von dem aus wir den gesamten Zustand des Internets beurteilen können. Aus diesem Grund benötigt jede Measurement Studie gezielt ausgewählte Beobachtungspunkte, die zur Forschungsfrage passen. In dieser Arbeit stellen wir drei verschiedene Beobachtungspunkte vor, die sich über die gsamte Internet-Topologie erstrecken— vom Rand bis zum Kern des Internets. Wir diskutieren ihre spezifischen Eigenschaften, ihre Eignung für verschiedene Klas- sen von Forschungsfragen und den Umgang mit den entsprechenden Daten. Die an den vorgestellten Beobachtungspunkten gewonnenen Datensätze ermöglichen uns die Durchführung von drei verschiedenen Measurement Studien und damit die folgenden Aspekte zu beleuchten: (a) Die Prävalenz von IP Source Address Spoofing bei einem großen europäischen Internet Exchange Point (IXP), (b) die Ausbreitungsdistanz von BGP-Communities, ein optionales transitives BGP-Attribut, das Anwendung im Bereich Traffic-Enigneering findet sowie (c) die Auswirkungen der globalen COVID- 19-Pandemie auf das Internet-Nutzungsverhalten an einem großen Internet Service Provider (ISP) und drei IXPs

BGP-Multipath Routing in the Internet

BGP-Multipath, or BGP-M, is a routing technique for balancing traffic load in the Internet. It enables a Border Gateway Protocol (BGP) border router to install multiple ‘equally-good’ paths to a destination prefix. While other multipath routing techniques are deployed at internal routers, BGP-M is deployed at border routers where traffic is shared on multiple border links between Autonomous Systems (ASes). Although there are a considerable number of research efforts on multipath routing, there is so far no dedicated measurement or study on BGP-M in the literature. This thesis presents the first systematic study on BGP-M. I proposed a novel approach to inferring the deployment of BGP-M by querying Looking Glass (LG) servers. I conducted a detailed investigation on the deployment of BGP-M in the Internet. I also analysed BGP-M’s routing properties based on traceroute measurements using RIPE Atlas probes. My research has revealed that BGP-M has already been used in the Internet. In particular, Hurricane Electric (AS6939), a Tier-1 network operator, has deployed BGP-M at border routers across its global network to hundreds of its neighbour ASes on both IPv4 and IPv6 Internet. My research has provided the state-of-the-art knowledge and insights in the deployment, configuration and operation of BGP-M. The data, methods and analysis introduced in this thesis can be immensely valuable to researchers, network operators and regulators who are interested in improving the performance and security of Internet routing. This work has raised awareness of BGP-M and may promote more deployment of BGP-M in future because BGP-M not only provides all benefits of multipath routing but also has distinct advantages in terms of flexibility, compatibility and transparency

Improving the Accuracy of the Internet Cartography

As the global Internet expands to satisfy the demands of the ever-increasing connected population, profound changes are occurring in its interconnection structure. The pervasive growth of IXPs and CDNs, two initially independent but synergistic infrastructure sectors, have contributed to the gradual flattening of the Internet’s inter-domain hierarchy with primary routing paths shifting from backbone networks to peripheral peering links. At the same time the IPv6 deployment has taken off due to the depletion of unallocated IPv4 addresses. These fundamental changes in Internet dynamics has obvious implications for network engineering and operations, which can be benefited by accurate topology maps to understand the properties of this critical infrastructure. This thesis presents a set of new measurement techniques and inference algorithms to construct a new type of semantically rich Internet map, and improve the state of the art in Internet cartography. The author first develops a methodology to extract large-scale validation data from the Communities BGP attribute, which encodes rich routing meta-data on BGP messages. Based on this better-informed dataset the author proceeds to analyse popular assumptions about inter-domain routing policies and devise a more accurate model to describe inter-AS business relationships. Accordingly, the thesis proposes a new relationship inference algorithm to accurately capture both simple and complex AS relationships across two dimensions: prefix type, and geographic location. Validation against three sources of ground-truth data reveals that the proposed algorithm achieves a near-perfect accuracy. However, any inference approach is constrained by the inability of the existing topology data sources to provide a complete view of the inter-domain topology. To limit the topology incompleteness problem the author augments traditional BGP data with routing policy data obtained directly from IXPs to discover massive peering meshes which have thus far been largely invisible

Improving Pan-African research and education networks through traffic engineering: A LISP/SDN approach

The UbuntuNet Alliance, a consortium of National Research and Education Networks (NRENs) runs an exclusive data network for education and research in east and southern Africa. Despite a high degree of route redundancy in the Alliance's topology, a large portion of Internet traffic between the NRENs is circuitously routed through Europe. This thesis proposes a performance-based strategy for dynamic ranking of inter-NREN paths to reduce latencies. The thesis makes two contributions: firstly, mapping Africa's inter-NREN topology and quantifying the extent and impact of circuitous routing; and, secondly, a dynamic traffic engineering scheme based on Software Defined Networking (SDN), Locator/Identifier Separation Protocol (LISP) and Reinforcement Learning. To quantify the extent and impact of circuitous routing among Africa's NRENs, active topology discovery was conducted. Traceroute results showed that up to 75% of traffic from African sources to African NRENs went through inter-continental routes and experienced much higher latencies than that of traffic routed within Africa. An efficient mechanism for topology discovery was implemented by incorporating prior knowledge of overlapping paths to minimize redundancy during measurements. Evaluation of the network probing mechanism showed a 47% reduction in packets required to complete measurements. An interactive geospatial topology visualization tool was designed to evaluate how NREN stakeholders could identify routes between NRENs. Usability evaluation showed that users were able to identify routes with an accuracy level of 68%. NRENs are faced with at least three problems to optimize traffic engineering, namely: how to discover alternate end-to-end paths; how to measure and monitor performance of different paths; and how to reconfigure alternate end-to-end paths. This work designed and evaluated a traffic engineering mechanism for dynamic discovery and configuration of alternate inter-NREN paths using SDN, LISP and Reinforcement Learning. A LISP/SDN based traffic engineering mechanism was designed to enable NRENs to dynamically rank alternate gateways. Emulation-based evaluation of the mechanism showed that dynamic path ranking was able to achieve 20% lower latencies compared to the default static path selection. SDN and Reinforcement Learning were used to enable dynamic packet forwarding in a multipath environment, through hop-by-hop ranking of alternate links based on latency and available bandwidth. The solution achieved minimum latencies with significant increases in aggregate throughput compared to static single path packet forwarding. Overall, this thesis provides evidence that integration of LISP, SDN and Reinforcement Learning, as well as ranking and dynamic configuration of paths could help Africa's NRENs to minimise latencies and to achieve better throughputs

Radiography of internet autonomous systems interconnection in Latin America and the Caribbean.

Lots of studies about the Internet Autonomous System (AS) level topology have been carried out during the last twenty years, most of them analyzing this topology on a world-wide scale, a lot of them based on routing information from the Border Gateway Protocol (BGP). However, studies focusing on a specific region and making comparisons between regions are not that popular and in fact, most world-wide studies are not valid in some particular regions. This work is targeting this particular problem of the regional or country topology analysis by enhancing regular AS-level graphs where to apply different connectivity metrics. The focus is set on Latin America and the Caribbean (the LAC region) which exhibits appropriate conditions for this type of analysis and where we show that a basic metric comparison may not be good enough so as to realize that there is a connectivity problem in the region. After concluding that the situation in the LAC region in terms of interconnection is even worse than expected, we perform some country-level studies finding correlations between graph characteristics and some socioeconomic indicators. We then use these correlations to identify countries in which it would be worth pushing for the deployment of an Internet Exchange Point (IXP), as simulating the creation of an IXP there has a great impact on the interconnection level and on the robustness of the regional Internet.The work done by Francisco Valera has been partially granted by the European Commission project LEONE (From local measurements to global management, grant number FP7-317647). The work done by Sofía Silva has been partially funded by IMDEA Networks.Publicad

Improving the accuracy of spoofed traffic inference in inter-domain traffic

Ascertaining that a network will forward spoofed traffic usually requires an active probing vantage point in that network, effectively preventing a comprehensive view of this global Internet vulnerability. We argue that broader visibility into the spoofing problem may lie in the capability to infer lack of Source Address Validation (SAV) compliance from large, heavily aggregated Internet traffic data, such as traffic observable at Internet Exchange Points (IXPs). The key idea is to use IXPs as observatories to detect spoofed packets, by leveraging Autonomous System (AS) topology knowledge extracted from Border Gateway Protocol (BGP) data to infer which source addresses should legitimately appear across parts of the IXP switch fabric. In this thesis, we demonstrate that the existing literature does not capture several fundamental challenges to this approach, including noise in BGP data sources, heuristic AS relationship inference, and idiosyncrasies in IXP interconnec- tivity fabrics. We propose Spoofer-IX, a novel methodology to navigate these challenges, leveraging Customer Cone semantics of AS relationships to guide precise classification of inter-domain traffic as In-cone, Out-of-cone ( spoofed ), Unverifiable, Bogon, and Unas- signed. We apply our methodology on extensive data analysis using real traffic data from two distinct IXPs in Brazil, a mid-size and a large-size infrastructure. In the mid-size IXP with more than 200 members, we find an upper bound volume of Out-of-cone traffic to be more than an order of magnitude less than the previous method inferred on the same data, revealing the practical importance of Customer Cone semantics in such analysis. We also found no significant improvement in deployment of SAV in networks using the mid-size IXP between 2017 and 2019. In hopes that our methods and tools generalize to use by other IXPs who want to avoid use of their infrastructure for launching spoofed-source DoS attacks, we explore the feasibility of scaling the system to larger and more diverse IXP infrastructures. To promote this goal, and broad replicability of our results, we make the source code of Spoofer-IX publicly available. This thesis illustrates the subtleties of scientific assessments of operational Internet infrastructure, and the need for a community focus on reproducing and repeating previous methods.A constatação de que uma rede encaminhará tráfego falsificado geralmente requer um ponto de vantagem ativo de medição nessa rede, impedindo efetivamente uma visão abrangente dessa vulnerabilidade global da Internet. Isto posto, argumentamos que uma visibilidade mais ampla do problema de spoofing pode estar na capacidade de inferir a falta de conformidade com as práticas de Source Address Validation (SAV) a partir de dados de tráfego da Internet altamente agregados, como o tráfego observável nos Internet Exchange Points (IXPs). A ideia chave é usar IXPs como observatórios para detectar pacotes falsificados, aproveitando o conhecimento da topologia de sistemas autônomos extraído dos dados do protocolo BGP para inferir quais endereços de origem devem aparecer legitimamente nas comunicações através da infra-estrutura de um IXP. Nesta tese, demonstramos que a literatura existente não captura diversos desafios fundamentais para essa abordagem, incluindo ruído em fontes de dados BGP, inferência heurística de relacionamento de sistemas autônomos e características específicas de interconectividade nas infraestruturas de IXPs. Propomos o Spoofer-IX, uma nova metodologia para superar esses desafios, utilizando a semântica do Customer Cone de relacionamento de sistemas autônomos para guiar com precisão a classificação de tráfego inter-domínio como In-cone, Out-of-cone ( spoofed ), Unverifiable, Bogon, e Unassigned. Aplicamos nossa metodologia em análises extensivas sobre dados reais de tráfego de dois IXPs distintos no Brasil, uma infraestrutura de médio porte e outra de grande porte. No IXP de tamanho médio, com mais de 200 membros, encontramos um limite superior do volume de tráfego Out-of-cone uma ordem de magnitude menor que o método anterior inferiu sob os mesmos dados, revelando a importância prática da semântica do Customer Cone em tal análise. Além disso, não encontramos melhorias significativas na implantação do Source Address Validation (SAV) em redes usando o IXP de tamanho médio entre 2017 e 2019. Na esperança de que nossos métodos e ferramentas sejam aplicáveis para uso por outros IXPs que desejam evitar o uso de sua infraestrutura para iniciar ataques de negação de serviço através de pacotes de origem falsificada, exploramos a viabilidade de escalar o sistema para infraestruturas IXP maiores e mais diversas. Para promover esse objetivo e a ampla replicabilidade de nossos resultados, disponibilizamos publicamente o código fonte do Spoofer-IX. Esta tese ilustra as sutilezas das avaliações científicas da infraestrutura operacional da Internet e a necessidade de um foco da comunidade na reprodução e repetição de métodos anteriores