Understanding the Reachability of IPv6 Limited Visibility Prefixes

The main functionality of the Internet is to provide global connectivity for every node attached to it. In light of the IPv4 address space depletion, large networks are in the process of deploying IPv6. In this paper we perform an extensive analysis of how BGP route propagation affects global reachability of the active IPv6 address space in the context of this unique transition of the Internet infrastructure. We propose and validate a methodology for testing the reachability of an IPv6 address block active in the routing system. Leveraging the global visibility status of the IPv6 prefixes evaluated with the BGP Visibility Scanner, we then use this methodology to verify if the visibility status of the prefix impacts its reachability at the interdomain level. We perform active measurements using the RIPE Atlas platform. We test destinations with different BGP visibility degrees (i.e., limited visibility LV, high visibility HV and dark prefixes). We show that the IPv6 LV prefixes (v6LVPs) are generally reachable, mostly due to a lessspecific HV covering prefix (v6HVP). However, this is not the case of the dark address space, which, by not having a covering v6HVP is largely unreachable.