Close Encounters of the ICMP Type 2 Kind (Near Misses with ICMPv6 Packet Too Big (PTB))

This document calls attention to the problem of delivering ICMPv6 type 2 "Packet Too Big" (PTB) messages to the intended destination (typically the server) in ECMP load-balanced or anycast network architectures. It discusses operational mitigations that can be employed to address this class of failures.