IGMP (Internet Group Management Protocol) allows hosts to dynamically join multicast groups and routers to manage delivery of multicast data packets. IGMP version 1 uses query and report messages between routers and hosts to discover which hosts belong to which multicast groups on local networks. Version 2 and 3 added new message types and formats to more efficiently manage group membership and enhance security.
3. IGMP v4 ver 1 Type : 1 query by multicast router : 2 response sent by host In a query group address is 0 In a report group address set to class D address 16 bit checksum Unused 8 bit 4-bit IGMP type 4-bit IGMP ver 32 bit class D group address
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6. IGMP v4 ver 2 0x11 = Membership Query There are two sub-types of Membership Query messages: - General Query, used to learn which groups have members on an attached network. - Group-Specific Query, used to learn if a particular group has any members on an attached network. 0x16 = Version 2 Membership Report 0x17 = Leave Group There is an additional type of message, for backwards-compatibility with IGMPv1: 0x12 = Version 1 Membership Report 16 bit checksum 8 bit Max response time 4-bit IGMP type 4-bit IGMP ver 32 bit class D group address
7. IGMP v4 ver 3 0x11 Membership Query 0x22 Version 3 Membership Report 0x12 Version 1 Membership Report [RFC-1112] 0x16 Version 2 Membership Report [RFC-2236] 0x17 Version 2 Leave Group [RFC-2236] Separate formats for query and response General query of group membership Specific query of a particular group address membership Query for a set of group address membership More enhancements for efficiency and security