After 50 years, the Internet is still defined as a collection of interconnected networks. Yet desires of countries for their own internet (Internet secession?), country-level firewalling, and persistent peering disputes all challenge the idea of a single set of interconnected networks. We show that the Internet today has peninsulas of persistent, partial connectivity, and that some outages cause islands where the Internet at the site is up, but partitioned from the main Internet. We propose a new definition of the Internet defining a single, global network while helping us to reason about peninsulas and islands and their relationship to Internet outages. We provide algorithms to detect peninsulas and islands, find that peninsulas are more common than outages, with thousands of /24s IPv4 blocks that are part of peninsulas lasting a month or more. Root causes of most peninsula events (45%) are transient routing problems. However, a few long-lived peninsulas events (7%) account for 90% of all peninsula time, and they suggest root causes in country- or AS-level policy choices. We also show that islands occur. Our definition shows that no single country can unilaterally claim to be the Internet, and helps clarify the spectrum from partial reachability to outages in prior work.
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