On 9/5/09 5:53 AM, Andrew Sullivan wrote:
I claim that we need to provide support for the network that people are actually building. That often includes things that we would not do ourselves, and that we think would be better done otherwise.
There are valid reasons to formally make statements about a practice, whether that rules the day is a different matter. There is a practice promoted, in respect to IPv4, where the dynamic nature of an IP address is to be divined by labels used in the reverse DNS PTR records. While a large number of legitimate MTAs publish PTR records, there is also a number that do not. This varies from region to region.
As a practical matter, does it make sense to continue this practice for IPv6? Our experience found that checking for these records has required much greater resources due to high levels of abuse and large numbers of reverse DNS timeouts delaying connection disposition. While legitimate MTA often have PTR records, not all do. Illegitimate MTA lacking an operational server in the reverse address space end up comprising the majority of traffic seen.
Keeping histories (persistent caches) about which MTAs offer which label type in their reverse entry can be handled in the IPv4 address space. As a practical matter, this is not easily done for IPv6. Does it make sense from an operational standpoint for ISPs to differentiate between residential services by using "different" labels in the reverse zone?
-Doug _______________________________________________ DNSOP mailing list [email protected] https://www.ietf.org/mailman/listinfo/dnsop
