The IPv6 Unrecognized Option
This document describes a method by which a source node can determine whether the underlying network can a) convey a packet that contains IPv6 destination options from itself to a destination node, and b) convey an ICMPv6 Parameter Problem message in the reverse direction. In order to support this method, this document defines a new IPv6 option, called the Unrecognized option. The Unrecognized option is not recognized by any destination node and always elicits an ICMPv6 Parameter Problem message.