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3.4. Source-Specific Joins

IGMPv3 allows receivers to join a group and specify they only want to receive traffic from specific sources. In this case, the DR can omit the (*,G) Join for the shared tree and only issue source-specific (S,G) Joins.

Source-Specific Multicast (SSM):

  • Address Range: IPv4 addresses from 232.0.0.0 to 232.255.255.255 are reserved for SSM
  • IGMPv3 Requirement: Receivers should only issue source-specific IGMPv3 Joins for this range
  • No Shared Tree: For SSM groups, routers should ignore non-source-specific Joins
note

For complete SSM specifications and IGMPv3 integration, see Section 3.4 of RFC 7761 and RFC 4607.

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