Active Probes

Has your computer received a probe from a CAIDA host?

You are seeing measurement probes from our Macroscopic Topology Project, a large-scale, publicly-funded Internet measurement initiative that is collecting connectivity, routing, and performance information about the wide-area infrastructure. We disseminate this information to network researchers in academia and industry as a public service (that is, without fee) for the purposes of promoting the engineering and maintenance of a robust, scalable global Internet infrastructure.

We are performing traceroute-like measurements of forward IP paths ('hops') from a source to many destinations, using a variety of measurement techniques (UDP packet to high port, ICMP ECHO_REQUEST, TCP SYN, etc.). For the most part, a target machine will receive just one probe packet per cycle, where a cycle currently lasts 2-3 days. However, if there is a firewall blocking incoming probes or blocking outgoing ICMP responses, then the firewall will see up to 15 packets (corresponding to 5 unresponsive hops at 3 tries per hop). Some destinations may see a higher packet rate if they are part of some particular sub-study.

We send probes to randomly-selected IP addresses with the goal of eventually probing a majority of all routed addresses, so it is impossible to contact and obtain permission from all destination host administrators prior to measurement.

Further information about the collected data can be found at the Routed /24 Topology Dataset page.

Thank you for your patience in this matter, please feel free to contact us if you have any further questions at trouble@caida.org.