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The TCP/IP Guide  9  TCP/IP Lower-Layer (Interface, Internet and Transport) Protocols (OSI Layers 2, 3 and 4)       9  TCP/IP Internet Layer (OSI Network Layer) Protocols            9  Internet Protocol (IP/IPv4, IPng/IPv6) and IP-Related Protocols (IP NAT, IPSec, Mobile IP)                 9  Internet Protocol Version 6 (IPv6) / IP Next Generation (IPng)                      9  IPv6 Addressing

IPv6/IPv4 Address Embedding 1 2 3 4 5 IPv6 Autoconfiguration and Renumbering

Multicast Scopes

The notion of explicitly scoping multicast addresses is important. Globally-scoped multicast addresses must be unique across the entire Internet, but locally-scoped addresses are unique only within the organization. This provides tremendous flexibility, as every type of multicast address actually comes in several “versions”: one that multicasts only within a node, one on the local link (local network), one on the local site and so on. The scope also allows routers to immediately determine how broadly they should propagate multicast datagrams, to improve efficiency and eliminate problems with traffic being sent outside the area for which it is intended. Figure 102 illustrates the notion of scope graphically (and it’s quite pretty, wouldn’t you say? J)

IPv6/IPv4 Address Embedding 1 2 3 4 5 IPv6 Autoconfiguration and Renumbering