ICANN Announcements

Read ICANN Announcements to stay informed of the latest policymaking activities, regional events, and more.

ICANN Publishes Name Collision Analysis Project (NCAP) Study 2 Documents

27 January 2022

Link to Public Comment Proceeding:


What We Need Your Input On

The Name Collision Analysis Project (NCAP) Discussion Group is seeking input on two draft work products that contribute to the NCAP Study 2 goals to understand how measurements taken at various layers of the Domain Name System (DNS) hierarchy convey the impact of name collisions, and to understand the impact of name collisions:

  • A Perspective Study of DNS Queries for Non-Existent Top-Level Domains (TLDs): This study aims to understand the distribution of DNS name collision traffic throughout the DNS hierarchy and provide insights into where and how DNS data can be collected and assessed. The NCAP Discussion Group presented two preliminary key findings with implications for how future assessments of name collision strings should be evaluated:
    • Finding 1: The IP addresses representing the most queries across the root server system (i.e., the "top talkers") are likely to query any given root server in two days, and queries from those IP addresses for non-existent top-level domains (TLDs) are likely to be found with similar prevalence on different root server identities.
    • Finding 2: Name collision traffic observed at the root is not sufficiently representative of traffic received at recursive resolvers to guarantee a complete and or accurate representation of a string's potential name collision risks and impacts.
  • Case Study of Collision Strings: Case studies of .corp, .home, .mail, .internal, .lan, and .local using DNS query data from A and J root servers. The case studies highlight changes over time of the properties of DNS queries and traffic alterations because of DNS evolution. The NCAP Discussion Group makes several observations including that queries for these undelegated names are increasing in volume and diversity, suggesting that challenges relating to impact and mitigation are also increasing.

Proposals for Your Input:


Name collision refers to the situation where a name that is defined and used in one namespace may also appear in another. Users and applications intending to use a name in one namespace may actually use it in a different one, and an unexpected behavior may result where the intended use of the name is not the same in both namespaces. The circumstances that lead to a name collision could be accidental or malicious.

On 2 November 2017, the ICANN Board passed resolutions (2017.11.02.29 – 2017.11.02.31) requesting the ICANN Security and Stability Advisory Committee (SSAC) to:

  • Conduct a study to present data, analysis and points of view, and provide advice to the Board regarding the risks posed to users and end systems if .CORP, .HOME, .MAIL strings were to be delegated in the root, as well as possible courses of action that might mitigate the identified risks.
  • Conduct a study to present data, analysis and points of view and provide advice to the Board on a range of questions regarding name collisions.

The SSAC responded with a proposal for three consecutive studies intended to address the Board's requests. In April 2019, the NCAP Discussion Group was formed to allow interested members of the ICANN community to participate in the NCAP effort.

The final NCAP Study 1 report, published on 19 June 2020, documented prior work on name collisions and assessed name collision datasets. In response to the findings of Study 1, the NCAP Discussion Group proposed a redesign of the proposed Study 2 to adjust the study goals, and have the NCAP Discussion Group undertake most of the work slated for paid contractors in the original version of the Study 2 proposal. On 3 March 2021, the ICANN Board directed the NCAP Discussion Group to proceed with Study 2 as redesigned.

The documents presented in this Public Comment proceeding contribute to the redesigned NCAP Study 2 goals to:

  • Understand the root cause of most name collisions
  • Understand the impact of name collisions

Next Steps

The NCAP Discussion Group will consider the input received during this Public Comment proceeding as it continues its work and develops the draft NCAP Study 2 report. The draft NCAP Study 2 report will be published for Public Comment.


ICANN's mission is to help ensure a stable, secure, and unified global Internet. To reach another person on the Internet, you need to type an address – a name or a number – into your computer or other device. That address must be unique so computers know where to find each other. ICANN helps coordinate and support these unique identifiers across the world. ICANN was formed in 1998 as a nonprofit public benefit corporation with a community of participants from all over the world.