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Stéphane Bortzmeyer

Location: Paris (France)

I work at AFNIC (the registry of .fr domain names), in the R&D department, on, among other things, DNS, security, statistics.

Pages created by Stéphane Bortzmeyer

Checking your Internet Connectivity with RIPE Atlas Anchors
Checking your Internet Connectivity with RIPE Atlas Anchors
Stéphane Bortzmeyer — Sep 14, 2015 05:05 PM

If you monitor your external Internet connectivity, you may wonder which machine is the best to ping. Hesitate no more - you can use RIPE Atlas anchors as landmarks.

The Many Instances of the L-root Name Server
The Many Instances of the L-root Name Server
Stéphane Bortzmeyer — Jan 20, 2014 04:50 PM

The techniques used by the L-root DNS server are documented in RFC 7108 "A Summary of Various Mechanisms Deployed at L-Root for the Identification of Anycast Nodes". These techniques can be used by the RIPE Atlas probes to find the instance of L-root they are talking to.

How Many RIPE Atlas Probes Can Resolve IPv6-only Domain Names?
Stéphane Bortzmeyer — Jan 13, 2014 09:05 AM

Each RIPE Atlas probe has at least one DNS resolver, indicated by a DHCP reply on the local network of the probe. Irrespective of the IP address of the resolver, this server may have IPv4 and IPv6 connectivity or only IPv4 connectivity. What is the percentage among RIPE Atlas probes?

All IP Addresses Are Equal? "dot-zero" Addresses Are Less Equal
Stéphane Bortzmeyer — Jul 03, 2013 11:00 AM

In theory, all IP addresses are the same, and you can allocate them at random without a problem. is certainly not better or worse than, right? But, in practice, certain IP addresses are regarded as "special" by some implementations and do not yield the same user experience. This is the case for the "dot-zero", IPv4 addresses in which the last byte is zero.

How Many RIPE Atlas Probes Believe They Have IPv6 (But Are Wrong)?
Stéphane Bortzmeyer — Jun 11, 2013 04:15 PM

To check the connectivity of an IPv6 device with RIPE Atlas, one typically asks N probes to ping the target and deduces the reachability of the target from the percentage of failures. But RIPE Atlas probes, like many IPv6 devices, often believe they are IPv6-connected while they are not.

Using RIPE Atlas User Defined Measurements to Find the Most Popular Instances of a DNS Anycast Name Server
Stéphane Bortzmeyer — May 03, 2013 09:30 AM

A DNS anycast name server has several physical instances, all behind the same IP address. Which one is used by a RIPE Atlas probe depends on the location of the probe in the BGP space. RIPE Atlas can query the physical identity of the probe and therefore help to determine which instances have the largest user base.

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