What Causal Forces Shape Internet Connectivity at the AS-level

摘要

Two ASs are connected in the Internet AS graph only if they have a business 'peering relationship.' By focusing on the AS subgraph ASpc whose links represent provider-customer relationships, we present an empirical study that identifies three crucial causal forces at work in the design of AS connectivity: (i) AS-geography, i.e., locality and number of PoPs (Points-of- Presence) within individual ASs; (ii) AS-specific business models, abstract toy models that describe how individual ASs choose their best provider; and (iii) AS evolution, a historic account of the lives of individual ASs in a dynamic ISP market. Based on these findings that directly relate to how provider- customer relationships may be determined in the actual Internet, we develop a new optimization-driven model for Internet growth at the ASpc level. Its defining feature is an explicit construction of a novel class of intuitive, multi-objective, local optimizations by which the different ASs determine in a fully distributed and decentralized fashion their 'best' upstream provider. We show that our model is broadly robust, perforce yields graphs that match inferred AS connectivity with respect to many different metrics, and is ideal for exploring the impact of new peering incentives or policies on AS-level connectivity.