According to the Online Etymology Dictionary, the verb collide is derived from the Latin verb collidere, which means, literally, “to strike together”:  com- “together” + lædere “to strike, injure by striking.”

Combined instead with loquium, or “speaking,” the com- prefix produces the Latin-derived noun colloquy: “a speaking together.”

Researchers and practitioners know well the benefits of the colloquium, the technical conference, a gathering of those speaking together on a topic.

So consider WPNC 14 – the upcoming namecollisions.net workshop – a colloquium on collisions: speaking together to keep name spaces from striking together.

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Many years ago on my first trip to London, I encountered for the first time signs that warned pedestrians that vehicles might be approaching in a different direction than they were accustomed to in their home countries, given the left-versus-right-side driving patterns around the world. (I wrote a while back about one notable change from left-to-right, the Swedish “H Day,” as a comment on the IPv6 transition.)

If you’re not sure on which side to expect the vehicles, it’s better to look both ways — and look again — if you want to reduce the risk of a collision.

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ICANN’s second-level domain (SLD) blocking proposal includes a provision that a party may demonstrate that an SLD not in the initial sample set could cause “severe harm,” and that SLD can potentially be blocked for a certain period of time. The extent to which that provision would need to be exercised remains to be determined. However, given the concerns outlined in Part 2 and Part 3 of this series, it seems likely that there could be many additions (and deletions!) from the blocked list given the lack of correlation between the DITL data and actual at-risk queries.

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As widely discussed recently, observed within the ICANN community several years ago, and anticipated in the broader technical community even earlier, the introduction of a new generic top-level domain (gTLD) at the global DNS root could result in name collisions with previously installed systems. Such systems sometimes send queries to the global DNS with domain name suffixes that, under reasonable assumptions at the time the systems were designed, may not have been expected to be delegated as gTLDs. The introduction of a new gTLD may conflict with those assumptions, such that the newly delegated gTLD collides with a domain name suffix in use within an internal name space, or one that is appended to a domain name as a result of search-list processing.

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As discussed in the several studies on name collisions published to date, determining which queries are at risk, and thus how to mitigate the risk, requires qualitative analysis (New gTLD Security and Stability Considerations; New gTLD Security, Stability, Resiliency Update: Exploratory Consumer Impact Analysis; Name Collisions in the DNS). Blocking a second level domain (SLD) simply on the basis that it was queried for in a past sample set runs a significant risk of false positives. SLDs that could have been delegated safely may be excluded on quantitative evidence alone, limiting the value of the new gTLD until the status of the SLD can be proven otherwise.

Similarly, not blocking an SLD on the basis that it was not queried for in a past sample set runs a comparable risk of false negatives.

A better way to deal with the risk is to treat not the symptoms but the underlying problem: that queries are being made by installed systems (or internal certificates are being employed by them) under the assumption that certain gTLDs won’t be delegated.

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For several years, DNS-OARC has been collecting DNS query data “from busy and interesting DNS name servers” as part of an annual “Day-in-the-Life” (DITL) effort (an effort originated by CAIDA in 2002) that I discussed in the first blog post in this series. DNS-OARC currently offers eight such data sets, covering the queries to many but not all of the 13 DNS root servers (and some non-root data) over a two-day period or longer each year from 2006 to present.  With tens of billions of queries, the data sets provide researchers with a broad base of information about how the world is interacting with the global DNS as seen from the perspective of root and other name server operators.

In order for second-level domain (SLD) blocking to mitigate the risk of name collisions for a given gTLD, it must be the case that the SLDs associated with at-risk queries occur with sufficient frequency and geographical distribution to be captured in the DITL data sets with high probability. Because it is a purely quantitative countermeasure, based only on the occurrence of a query, not the context around it, SLD blocking does not offer a model for distinguishing at-risk queries from queries that are not at risk.  Consequently, SLD blocking must make a stronger assumption to be effective:  that any queries involving a given SLD occur with sufficient frequency and geographical distribution to be captured with high probability.

Put another way, the DITL data set – limited in time to an annual two-day period and in space to the name servers that participate in the DITL study – offers only a sample of the queries from installed systems, not statistically significant evidence of their behavior and of which at-risk queries are actually occurring.

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