I have reviewed this document as part of the security directorate's ongoing effort to review all IETF documents being processed by the IESG. These comments were written primarily for the benefit of the security area directors. Document editors and WG chairs should treat these comments just like any other last call comments. This document describes IPv6 Neighbor Discovery (ND) operational problems encountered IPv6 routers. The root issue is the large subnet sizes that are typically used, where a router naively reacting to the discovery of IPv6 addresses within an entire subnet can cause resource exhaustion issues. The document suggests techniques that protocol implementors and operators can employ to mitigate the resource exhaustions. The document adequately describes the resource exhaustion as a DoS opportunity. The advice itself does not appear to create any new DoS considerations. I believe it is ready to publish. Brian