Resolver side mitigations
Describes mitigations against spoofing attacks on DNS, including: (1) Repeating the query, including techniques for handling non-deterministic responses. (2) Prepending a random nonce to the question where a referral is probable. (3) Estimating the entropy available, taking into account (a) Observed packets with incorrect IDs. (b) Records where the owner name does not match the question. (c) The previous content of the cache.