Tom Lanyon <tom+nanog@oneshoeco.com> opined:
OK.. let's say you're a DSL provider. Are you going to have your DHCP server populating the forward and reverse DNS? With what, the account holder's name? somename.example.com ?
I'll suggest that (a) IF the addresses do migrate among different customers of the ISP, (b) the addresses handed out are publicly routable, AND (c) the CPE has to 'authenticate' itself to the head-end, then it is _very_ useful *to*the*ISP* to have dynamically-assigned DNS records of the form: cust.{accountid}.{locationid}.ISP.{com/net/TLD} or something of the sort.
Something of that sort can save a -lot- of time/effort in identifying the customer involved in a complaint.
Surely that's only useful if they're still allocated the address at the time of investigating said complaint; a dynamically updating DNS record like thi s is really no substitution for accurate accounting records in your RADIUS s ystem.
You're missing some 'obvious' considerations. Consider a spam complaint sent with 'full headers' included. The rDNS _at_the_time_of_the_crime_ is present in the complaint. Yes, you need to confirm that -that- customer was on that IP at that time -- but having an identifier for the customer makes the verification check much quicker/simpler, and requires less skils on the part of the front-line person dealing with the complaint. No, it doesn't *always* provide a short-cut to identification, but it is useful "often enough' to be well worth considering.