Steven, take it easy please. Given the first few replies I received, allow me to clarify, now that I've successfully hijacked the thread and apparently angered the anti-spam crowd: I am quite aware of the problem and do not disagree that there needs to be a way to identify what IP endpoints are residential CPE. I simply have some problems with /this/ current incarnation of a best practice, and I was querying whether it had applicability outside of the SORBS/Trend Micro world. Honestly, I feel that PTRs are the least reliable way to make such a decision. Depending on the chain of delegation, a server operator may not have access to modify his PTR record and might not be able to change it. Several operators have annoyingly odd delegation patterns. PTRs are just bad news for any kind of useful decision on, other than "PTR-matches-A". Given the amount of IRC abuse PTRs have seen, the consequential abuse of IPv4 allocation to support exotic PTRs, and the resulting limitation of PTR alteration that many providers practice I just don't like PTRs overall for anything meaningful. I also disagree with space being assumed dynamic unless it is declared static -- helpfully, I have been reminded that consumer CPE equipment is a large number of IPv4 endpoints, but I still think space should be assumed static unless declared dynamic. The burden really should be upon the providers of dynamic services to inform us that their allocations are a dynamic pool; good luck with this, however. Getting a standards-track solution that is reliable, cost-effective for home Internet providers to get on board with, and that has very little wiggle-room for discretion (this current incarnation has quite a bit) is necessary for me to be on board with such classification techniques. That said, I am not the guru that others on this list are and I am unprepared to present an alternative; I am simply pointing out that I'd like to see an alternative. Let me reiterate: I'm not disputing the challenges that network operators face with network abuse, I am simply disagreeing with this draft, its authorship, the sour taste you get from reading it because it's so far past expiration, and its motives in current practice. It's akin to me disagreeing with daylight savings time because it tries to fix energy consumption from lighting. JS