Sibling Prefixes: Identifying Similarities in IPv4 and IPv6 Prefixes

We introduce the concept of a sibling prefix as an IPv4 and IPv6 prefix pair with similar services (i.e., IPv4 and IPv6 prefixes sharing similar domain names). On this website, we present results from our ongoing Sibling Prefixes measurements and provide fellow researchers with access to the measurement dataset. For methodology and details, see Sibling Prefixes: Identifying Similarities in IPv4 and IPv6 Prefixes.

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Referencing the Sibling Prefixes: Identifying Similarities in IPv4 and IPv6 Prefixes

If you are using data from the Sibling Prefixes: Identifying Similarities in IPv4 and IPv6 Prefixes in your publication, please cite it with the following reference: @inproceedings{osali2025sibling,
   title = {Sibling Prefixes: Identifying Similarities in IPv4 and IPv6 Prefixes},
   author = {Osali, Fariba and Sediqi, Khwaja Zubair and Gasser, Oliver},
   booktitle = {ACM Internet Measurement Conference 2025},
   year = {2025},
   month = oct,
   doi = {10.1145/3730567.3732917}
}

Paper

Download paper: Sibling Prefixes: Identifying Similarities in IPv4 and IPv6 Prefixes

Abstract. Since the standardization of IPv6 in 1998, both versions of the Internet Protocol have coexisted in the Internet. Clients usually run algorithms such as Happy Eyeballs, to decide whether to connect to an IPv4 or IPv6 endpoint for dual-stack domains. To identify whether two addresses belong to the same device or service, researchers have proposed different forms of alias resolution techniques. Similarly, one can also form siblings of IPv4 and IPv6 addresses belonging to the same device. Traditionally, all of these approaches have focused on individual IP addresses. In this work, we propose the concept of “sibling prefixes”, where we extend the definition of an IPv4-IPv6 sibling to two IP prefixes one IPv4 prefix and its sibling IPv6 prefix. We present a technique based on large-scale DNS resolution data to identify 76k IPv4-IPv6 sibling prefixes. We find sibling prefixes to be relatively stable over time. We present SP-Tuner algorithm to tune the CIDR size of sibling prefixes and improve the perfect match siblings from 52% to 82%. For more than half of sibling prefixes, the organization names for their IPv4 and IPv6 origin ASes are identical, and 60% of all sibling prefixes have at least one of the prefixes with a valid ROV status in RPKI. Furthermore, we identify sibling prefixes in 24 hypergiant and CDN networks. Finally, we plan to regularly publish a list of sibling prefixes to be used by network operators and fellow researchers in dual-stack studies.

Authors. Fariba Osali, Khwaja Zubair Sediqi, Oliver Gasser.

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