IPv4 Source-Specific Multicast (SSM) address reservation

Source-Specific Multicast (SSM) is defined in RFC 4607. Source-Specific Multicast (SSM) identify multicast hosts not only by group address but also by source. ICANN/IANA has reserved IPv4 Class D address range 232.0.0.0/8 for Source-Specific Multicast (SSM).

Source-specific multicast (SSM) is a type of multicast where multicast clients can request the multicast packets from specific sources, with source addresses.

IGMPv3 has suppot for "source filtering". "source filtering" is the feature in IGMPv3 where multicast clients can specify in receiving packets only from specific source addresses. Any-source multicast (ASM) is another type where receiver indicates that it can receive multicast packets from any-source.

IPv4 Class D multicast addresses from 232.0.0.0 to 232.255.255.255 are reserved as Source Specific Multicast (SSM) block.