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IPv6 Prefix Discovery

IPv6 Prefix Discovery. Murray S. Kucherawy <msk@cloudmark.com>. Today. IPv4-based email abuse prevention relies heavily on a database of IP addresses with “bad reputations” A database of addresses is no larger than 4.3 billion entries (of course)

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IPv6 Prefix Discovery

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  1. IPv6 Prefix Discovery Murray S. Kucherawy <msk@cloudmark.com>

  2. Today • IPv4-based email abuse prevention relies heavily on a database of IP addresses with “bad reputations” • A database of addresses is no larger than 4.3 billion entries (of course) • Most popular expression of these is the RBL (Realtime Block List, RFCxxxx), which is published via the DNS

  3. RBLs • Query: 1.2.3.4.rbl-root, ask for “A” • Reply: NXDOMAIN, or 127.0.0.1 • Or sometimes the octets in the reply encode reputation data • Caching and redundancy keep this functional and practical • …so far

  4. IPv6 • Vastly larger address space • Not practical to consider tracking reputation about each of them • No standard delegation size; commonly between /48 and /64 • A spammer could send junk from such a network and rarely, if ever, re-use a single address

  5. RBLs under IPv6 • Ignoring database size for a moment, this still won’t work • A spammer changing IP address quickly will mean caching of previous answers becomes useless • And other cached data will be flushed because of space limits • So this would clobber the DNS in general

  6. What’s needed • We need to be able to figure out , given an IP address, the size of the endpoint delegation • Allows address aggregation by reputation systems • Keeps the query space about the same as it is for IPv4 now • IRTF has an idea out there that allows the DNS to express IP ranges

  7. Some ideas • Publish it via WHOIS • WHOIS isn’t standard and doesn’t seem scalable • Some registrars can’t be trusted to publish real data • Get it from BGP • MTAs don’t really have access to BGP data • We’d need a standard interface to exchange it between the lower layers and the higher ones

  8. Can you help? • Does this working group’s mandate fit the idea of exploring this? • Or does it belong in some other WG? • How would you suggest we go about doing this?

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