Authentication-only Mode for Secure DHCPv6

Secure DHCPv6 includes mechanisms for encryption and authentication, where encryption is currently mandated due to concerns for pervasive monitoring in the Internet. The Secure DHCPv6 specification states that the mechanisms are applicable in any environment where physical security on the link is not assured and attacks on DHCPv6 are a concern. However, this document presents a reference use case where physical and/or link-layer security are already assured. This document therefore proposes an authentication-only application of Secure DHCPv6 when there is already sufficent protection against pervasive monitoirng.