The purpose of the MLD protocol in the IPv6 multicast architecture is to allow an IPv6 router to discover the presence of multicast listeners on directly-attached links and to discover which multicast addresses are of interest to neighboring nodes. MLD is the direct IPv6 replacement for the IGMP protocol used in IPv4. The MLD implementation described in this document is based on the MLDv2 standard, which is a backward-compatible update to the MLDv1 standard.
There are three versions of IGMP, and two versions of MLD. IGMPv2 is equivalent in function to MLDv1 and IGMPv3 is equivalent to MLDv2.