On Mon 15/Apr/2024 13:16:50 +0200 Douglas Foster wrote:
Our original choice of N was based on the PSL. The PSL could not detect organizational boundaries could not boundaries below level 5, because it had no entries longer than 5 labels, and we determined that the 5-label entries were not used for mail. Therefore, any increase in N is new capability. That new capability is probably desirable, but need not be limitless. Using an N of 8 introduces a lot of new capability.
8 is not needed and not justified. A mail site using 8 labels would have troubles with the RFC 7489 version, which uses the PSL. They'd have to ask for PSL upgrades, right?
Now, we can relax our ambition to be PSL-free and state N=max number of labels of public suffixes used by mail. Or we could put N in an IANA registry that can be updated by expert review. Such methods allow to have N low enough, yet upgradable and equal for all (compliant) implementations.
Otherwise we can drop the requirement that N be equal for all implementations, and just make it configurable. After all, it is an anti-abuse measure, akin to SPF lookup limit. We can also keep it fixed at 5 and be sure that implementations will differ anyway.
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