RFC1918 outlined special blocks of IP v4 Address ranges for private use in the realm of Numbers. Doing something similar for Names is a good, wise and logical step forward, so this is a positive evolution of the namespace by ICANN/IANA in my opinion, as it brings some parity between the two N's in ICANN.

The .INTERNAL TLD creation is noteworthy for a number of reasons, key among them being that absent something being intentionally and deliberately defined like this, there have been many self-defined namespaces created across the span of decades for diverse private use.

I comment because this special-use domain, .INTERNAL will likely be used widely, and there will likely be be use-cases that are going to require cookie isolation or SSL issuance, and I wonder if there is an opportunity to have some subdomains be defined for purpose within .INTERNAL as it launches, so that these can be universally applicable and used in a consistent and predictable manner.

I have been a core maintainer of the Public Suffix List (PSL) https://github.com/publicsuffix/list since 2008, which is a resource that is used for advancing Universal Acceptance and general domain name elegance within browsers and applications, and have worked to ensure that it adheres to strict conformance with ICP-3 and follows the root as published by the IANA/ICANN.

For those unfamiliar with the PSL, it is essentially a version of the root that includes deeper descent into the second or further level, adding more elegance within the namespace. An example of this is where the IANA list is .UK, the PSL would have .UK, but also include the descending .AC.UK, .CO.UK,.ORG.UK, etc.

Primarily, the PSL is used for understanding the apex of a given namespace, for the purpose of cookie segmentation, but it has been widely used for a non-exhaustive number of other reasons such as the issuance (or non-issuance) of wildcard certificates, sub-domain account creation, DMARC and other areas.

What I believe to be the case is that designating some subdomain at "launch" of .INTERNAL, say EXAMPLE.INTERNAL or PRIVATE.INTERNAL (or some other designated subdomain), and then submitting that to the PSL would allow for browsers or other systems, apps or processes to use that as a subspace horizon for testing of activities that they would typically request a PSL entry for in order to test or develop.

Thank you,

Jothan Frakes

(Submitted personally as a maintainer of the PSL, and not in my role as Co-Chair of the CPH Techops or Executive committee of the RrSG)

Designating some subdomain at "launch" of .INTERNAL, say EXAMPLE.INTERNAL or PRIVATE.INTERNAL (or some other designated subdomain), and then submitting that to the Public Suffix List (PSL) https://github.com/publicsuffix/list would allow for browsers or other internet applications that absorb and use the PSL to use that as a subspace horizon for testing of activities that they would typically request a PSL entry for in order to test or develop.