Internet Protocol supplies an inter-network datagram interface. Its basic packet delivery does not itself guarantee arrival, order, absence of duplicates or completion of an application operation. IPv4 and IPv6 are versions of this network-layer protocol.
IP multicast sends an Internet Protocol datagram to a group identified by a multicast IP address. Delivery retains the underlying best-effort nature of Internet Protocol.
Multicast routing establishes and maintains the forwarding decisions that deliver group-addressed packets to interested receivers.
Reverse path forwarding accepts a source's multicast traffic only on the interface selected for the reverse route to that source. With consistent loop-free routing, those parent choices define a source-rooted tree. Membership pruning can then remove unneeded branches.
A multicast distribution tree describes the parent and outgoing branches used to distribute packets to a group. Source-rooted and shared-group designs make different state and path choices.
IPv6 uses 128-bit addresses and a revised packet format. More address space does not remove firewalls or decide which application providers must be trusted.[ref]
Internet Protocol, Version 6 (IPv6) Specification (RFC 8200). §1: expanded addressing and other protocol changes
IPv4 uses 32-bit addresses. Address sharing through network address and port translation is one response to pressure on its globally usable address space.
An IP address identifies an interface or destination according to the relevant Internet Protocol addressing rules. It is not inherently the identity of a person, and address translation can change the address visible across a boundary.
