LACeS Explorer

Quick summary:

• Use (AB > 3) || (GCD > 1) when high confidence is needed.
• Use (AB > 1) || (GCD > 1) (i.e. all prefixes) when completeness is needed.

False positives (AB). The anycast-based approach (AB) can produce false positives — especially when AB reports fewer than 3 sites. This is a known limitation of the underlying methodology; see MAnycast2.

False negatives (GCD). The latency-based approach (GCD) is highly accurate, but may miss prefixes deployed only in small geographic regions (regional anycast).

Partial anycast. Because probing runs at /24 granularity, some prefixes contain a mix of unicast and anycast addresses. Around 1,000 /24s are partially anycast (identified via bi-annual /32 scans). These are flagged with the partial column, but the flag may not reflect short-term changes.

Each row in the dataset represents one /24 (IPv4) or /48 (IPv6) prefix detected as anycast by at least one method. Column meanings:

Both AB and GCD consider anycast confirmed when the number of detected sites is greater than 1. The backing_prefix and ASN columns are sourced from CAIDA's prefix2as.

IPv4. The ICMP hitlist uses the USC/ISI ANT IPv4 hitlist — one likely-responsive IP per /24. The DNS hitlist draws from public DNS nameservers and OpenINTEL infra:ns. The TCP hitlist uses large-scale ZMap SYN/ACK scans. All hitlists are refreshed quarterly in sync with the USC/ISI release.

IPv6. AAAA record addresses from OpenINTEL and TUM's IPv6Hitlist. To keep probing times manageable, only the first /48 of aliased prefixes is scanned. For a more complete view, join with TUM's aliased-prefix set.

The census runs daily and is updated in this repository automatically.

If you use this dataset in academic work, please cite:

Hendriks, Luckie, Jonker, Sommese, van Rijswijk-Deij. LACeS: An Open, Fast, Responsible and Efficient Longitudinal Anycast Census System. IMC 2025. doi:10.1145/3730567.3764484

@inproceedings{10.1145/3730567.3764484,
  author    = {Hendriks, Remi and Luckie, Matthew and Jonker, Mattijs
               and Sommese, Raffaele and van Rijswijk-Deij, Roland},
  title     = {LACeS: An Open, Fast, Responsible and Efficient
               Longitudinal Anycast Census System},
  booktitle = {Proceedings of the 2025 ACM Internet Measurement Conference},
  year      = {2025},
  pages     = {445--461},
  doi       = {10.1145/3730567.3764484},
  series    = {IMC '25}
}

All tooling is publicly available under MPL 2.0:

• MAnycastR — measurement tooling for AB and GCD measurements.
• MiGreedy — optimised implementation of the iGreedy latency-based geolocation algorithm.

This census depends on the following publicly available datasets and resources: