Anycast Scanning

This measurement probes into anycast prefixes, with all of the Atlas probes working as a team to rotate through all measurement targets. This "team probing" is facilitated by a DNS rendez-vous technique described here: https://labs.ripe.net/author/emileaben/measuring-more-internet-with-ripe-atlas/ . The list of anycast IPs (ie. a single ICMP responding IP address for all detected anycast prefixes) is taken from https://github.com/bgptools/anycast-prefixes at 00:00 UTC

This measurement is potentially useful for:

• finding IXPs close to probes (under the assumption that a decent amount of anycast is done at IXPs).
• inspection of anycast catchment areas relative to RIPE Atlas probe deployments.
• (as a corollary): finding which IXPs don't have RIPE Atlas probes close by

Measurement IDs:

• IPv4: 63868161
• IPv6: 63868190

Measurement tag: "anycast"

Considerations for measurement creation: interval is 900 (default), and the 'spread' parameter is set to 450 , to make sure the DNS rendez-vous point will be hit as distributed over time as possible (ie. avoid overload and/or all kinds of cache TTL violation effects) Paris ID is set to 1, in an attempt to capture 1 specific state between a source and dest. In case one would want to make a traceroute between the same src/dst with a Paris ID of 1, this might reproduce the same flow ID (TODO: check with probe code) The protocol was set to ICMP because limited testing revealed that for some networks (notably cloudflare), a UDP trace had multiple different IPs in the same hop, which complicates analysis.