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Appendix B. Summary of Changes from IGMPv2

The following is a summary of the changes from IGMPv2 [RFC2236] to IGMPv3:

  1. Source Filtering: The ability for hosts to specify which sources they want to receive (INCLUDE mode) or which sources they want to block (EXCLUDE mode).

  2. Group Record Types: IGMPv3 Reports contain Group Records, which can be of different types (Current State, Filter Mode Change, Source List Change) to convey different kinds of information.

  3. Membership Report Format: The Report format has been completely redesigned to support multiple Group Records in a single message and to carry source addresses.

  4. Query Format: The Query format has been extended to support Group-and-Source-Specific Queries and to carry the Robustness Variable and Query Interval (QQIC).

  5. Max Resp Code: The Max Resp Code field has been redefined to support larger values using a floating-point representation.

  6. Querier Election: The Querier election mechanism remains the same, but the rules for handling older versions have been clarified.

  7. S Flag: The "Suppress Router-Side Processing" flag in Queries allows routers to suppress timer updates when receiving Queries, which is useful for certain diagnostics or special configurations.

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