Hello Marc, It depends what you are looking for. Though the same AS path is measured between two ASes, the IP level paths could be different, which leads to different RTT behaviour. I analysed the RTT over 12h between 100 probes in AS3215 and m-root. The resulted times series demonstrate different level of variation. Further, it turned out that most variation in end2end RTT measurements takes place in access network, with the help of traceroute. So if you are looking to quantify the performance of AS level path, choose the ping trace with the least variation. For more detail, W. Shao, J.-L. Rougier, F. Devienne, and M. Viste, “Improve Round-Trip Time Measurement Quality via Clustering in Inter-Domain Traffic Engineering,” no. AnNet, pp. 1105–1108, 2016. My two cents, wenqin ----- Mail original ----- De: "Marc Sanchez" <marc.sanchez@csuc.cat> À: ripe-atlas@ripe.net Envoyé: Mercredi 11 Mai 2016 17:52:06 Objet: [atlas] Number of probes I'm new in RIPE and I don't know it enough deeper. I need to check the state of several networks and I'm wondering how many probes should I need to measure a ping between two ASN. Could be enough using just one probe for each measurement? Sorry for the inconvenience. Sent via RIPE Forum -- https://www.ripe.net/participate/mail/forum