Member： Malte Tashiro
Category: Exploring
- Background：The Internet is a continuously growing system of networks. The increasing structural complexity makes it difficult to understand all aspects of the system. In addition, the topology of the Internet can be represented in different ways, for example, as a map of physical cables, or more abstract as a mesh of connected networks.
- Purpose：Develop methods that infer dependencies from the Internet topology and increase knowledge about the Internet’s infrastructure by applying different levels of abstraction and performing a cross-layer analysis.
IXP Dependency Analysis
Internet exchange points (IXPs) play a vital role in the modern Internet. Envisioned as a means to connect physically close networks, they have grown into large hubs connecting networks from all over the world, either directly or via remote peering. It is therefore important to understand the real footprint of an IXP to quantify the extent to which problems (e.g., outages) at an IXP can impact the surrounding Internet topology. An IXP footprint computed only from its list of members as given by PeeringDB, or the IXP’s website, is usually depicting an incomplete view of the IXP as it misses downstream networks whose traffic may transit via an IXP although they are not directly peering there. In this paper we propose a robust approach that uncovers this dependency using traceroute data from two large measurement platforms. Our approach converts traceroutes to paths that include both autonomous systems (ASes) and IXPs and computes AS Hegemony to infer their inter-dependencies. This technique discovers thousands of dependent networks not directly connected to IXPs and emphasizes the role of IXPs in the Internet topology. We also look at the geolocation of members and dependents and find that only 3% of IXPs with dependents are entirely local: all members and dependents are in the same country as the IXP. Another 52% connect international members, but only have domestic dependents.
Alternate BGP Path Detection
Internet topology analysis based on BGP data only captures the active paths in the topology. This is because route collectors receive only preferred routes from their peers. As a consequence, it is hard to predict whether a failure of a network implies a failure of its dependents, or if the dependents have an alternative link available as a fail-over.
The goal of this research is to perform a systematic analysis of networks that exhibit a strong dependency relationship. We use BGP poisoning to force a change of the topology and monitor if the dependent network is still able to reach an experimental prefix.
Initial results show that especially large networks (e.g., AS4713 / OCN depending on AS2914 / NTT) have no alternative path available, indicating that a failure of the parent network would lead to a disconnect from large parts of the Internet for the dependent.