LACeS Explorer

The LACeS anycast census relies on two primary measurement platforms to identify and geolocate anycast deployments:

• TANGLED Anycast Testbed: Used for the Anycast-Based (AB) component. LACeS utilizes 32 globally distributed nodes from TANGLED to send synchronized probes (ICMP, TCP, DNS) to each target, identifying unique responding sites. See: research paper
• CAIDA Archipelago (Ark): Used for the Great Circle Distance (GCD) component. We leverage latency measurements from a large number of geographically distributed Ark vantage points to geolocate anycast sites by applying the "speed-of-light" constraint. See: research paper

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. Each protocol has its own hitlist with up to five ranked targets per /24, probed in order until one responds. Every hitlist starts with anycast targets from earlier censuses, addresses that responded to the same protocol in the last 7 daily censuses, and bgp.tools' anycast-prefixes. The ICMP hitlist adds the USC/ISI ANT IPv4 hitlist and OpenINTEL A record addresses; the TCP hitlist adds OpenINTEL A record addresses. The DNS hitlist adds name servers from OpenINTEL infra:ns and the DNS Dependency Graph, open resolvers from ODNS, and public DNS nameservers. All hitlists are rebuilt weekly.

IPv6. The same structure at /48 granularity. ICMP and TCP use AAAA record addresses from OpenINTEL, TUM's IPv6Hitlist (ICMP, TCP/80 and TCP/443 responsive addresses), and TU Dresden & HAW Hamburg's IPv6-SRA hitlist. DNS uses name servers from OpenINTEL infra:ns and the DNS Dependency Graph, public DNS nameservers, and TUM's UDP/53 responsive addresses. 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 · PDF

@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.

The LACeS census data is available programmatically via a REST API hosted on this server. All endpoints return JSON and require no authentication.

Full documentation with parameter descriptions, response schemas, and interactive examples: Swagger UI · ReDoc

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