Internet Group Management Protocol (IGMP) and Multicast Listener Discovery (MLD) are the Multicast Group Membership Discovery (MGMD) protocols. They are essentially the same protocol, with IGMP used for IPv4 multicast groups and MLD used for IPv6 multicast groups. These protocols are used between end systems (often desktops) and the multicast router to request data for a given multicast group.There have been three versions of IGMP, and two versions of MLD. IGMPv2 is equivalent in function to MLDv1 and IGMPv3 is equivalent to MLDv2. All versions of IGMP/MLD are widely deployed. For example, an IGMP/MLD host implementation is included in some operating systems, and the following table shows the level of support for IGMP in Microsoft Windows hosts.