Sub-Link Scoped IPv6 Multicast Addressing

The IPv6 addressing architecture for multicast has the scope of a multicast group embedded in its address, with the smallest non- reserved scopes being interface-local and link-local, numbered 1 and 2. This document suggests the introduction of a scope inbetween these two, for use with lower-layer transport multicast that reaches parts of a link. Since there is no room to insert a scope value for this, a separate address block is used. A mapping for Ethernet as lower-layer transport is provided.