IPv6 intentionally deprecates fragmentation by routers in the network. Instead, links with restricting Maximum Transmission Units (MTUs) must either drop each too-large packet and return an ICMPv6 Packet Too Big (PTB) message or perform link-specific fragmentation and reassembly (also known as "link adaptation") at a layer below IPv6. This latter category of links is often performance-challenged to accommodate steady-state link adaptation. This document therefore proposes an update to the base IPv6 specification to better accommodate links that require link-specific adaptation.