IGMP <ul><li>Multicast data-gram received by a host is to be delivered one or more processes </li></ul><ul><li>Hosts may belong to many networks </li></ul><ul><li>Routers have to know registered hosts for delivery of data-gram </li></ul><ul><li>Hosts can dynamically join or leave the host group </li></ul><ul><li>IGMP efficiently manages above operations </li></ul>
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
IGMP v4 ver 1 protocol <ul><li>Multicast routers send Host Membership Query messages to discover which host groups have members on their attached local networks. </li></ul><ul><li>Queries are addressed to the all-hosts group (address 188.8.131.52), and carry an IP TTL = 1. </li></ul><ul><li>Hosts respond to a Query reporting each host group to which they belong on the network interface from which the Query was received. </li></ul><ul><li>Host reports are delayed by D second interval instead of all occurring at once. </li></ul><ul><li>In normal case, only one host report will be generated for each group present on the network, by the member host whose delay timer expires first. </li></ul>
IGMP v4 ver 1 protocol <ul><li>Multicast routers send Queries periodically </li></ul><ul><li>If no host reports are received for a particular group after some number of Queries, the routers assume that that group has no local members </li></ul><ul><li>When a host joins a new group, it should immediately transmit a host report for that group </li></ul><ul><li>Host does not send a message on leaving a group </li></ul>
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
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
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