Networks connected to the Internet rely on other networks (a.k.a ASes) to transmit data. Consequently, the connectivity of a network depend on the connectivity of other networks. AS hegemony is a metric to evaluate these AS-interdependences based on BGP data. See our research report for more details: https://www.iij-ii.co.jp/en/members/romain/pdf/romain_pam2018.pdf
Let's look at an example, AS2497 IIJ is one of the main ISP in Japan. For the second week of January 2018 we obtain the two following plots:
The top plot shows the AS dependencies of AS2497. That means the most common transit networks used to reach AS2497. The value (a.k.a AS hegemony) range between 0 and 1. The value represents the ratio of AS paths towards AS2497 that contain a certain AS transit. Values close to 1 mean that the reachability of the monitored AS is strongly depending on a transit AS. The plot shows only three weak dependencies to Level(3) (AS3356), NTT America (AS2914), and GTT (AS3257). Around mid-February, 14% of the paths towards IIJ transit through Level(3), 12% through NTT, and 3% through GTT. Stub ASes usually have much higher values, for example the values goes up to 1 for ASes with a single upstream provider (meaning that all the paths include the upstream provider). You can click on the graph to display dependencies details at particular timestamp and a graphical representation of BGP changes around that time (using BGPlay).
The bottom plot shows the number of networks that depend on AS2497. In this case there is about 400 networks that use IIJ for transit. This is somehow related to IIJ's customer cone. The main difference is that networks using IIJ as a backup transit are not counted here whereas they are counted in its customer cone. You can click on the graph to obtain an overview of dependent networks and a link to the complete list of networks.
Level shift for an entire day. Sometimes we cannot get as much data as we'd like, if the amount of data is very low then graphs might show significant level shifts for the entire day.
Update frequency. For now AS interdependence results are daily updated. We are planning to make it near-real time in a near future.