TABLE OF CONTENTS This section looks at some more detailed information related to address types. We discuss a number of unicast addresses, multicast addresses, and anycast addresses.
A unicast address identifies a single interface within the scope of the unicast address type. This could be a VoIP handset in a VoIPv6 environment, a PC on a LAN, a terminal in a VSAT network and so on. Utilizing an up-to-date unicast routing topology, Protocol Data Units (PDUs) addressed to a unicast address are delivered to a single interface. Unicast addresses fall into the following categories:
Aggregatable global unicast addresses (e.g., used to reach an Internet-connected VoIP phone)
Link-local addresses (e.g., used to reach a VoIP phone on the same LAN segment)
Special addresses, including unspecified and loopback addresses
Compatibility addresses, including 6to4 addresses
These are discussed next.
The IPv6-based Internet has been designed to support efficient, hierarchical addressing and routing (this is in contrast IPv4-based Internet, which has a mixture of both flat and hierarchical routing). Aggregatable global unicast addresses are globally routable and globally reachable on the IPv6 portion of the (IPv6) Internet. The region of the Internet over which the aggregatable global unicast address is unique (the scope) is the entire IPv6 Internet. As we saw earlier, aggregatable global unicast addresses (aka global addresses), are identified by the format prefix of 001. This type of addressing can be used, for example, to reach an Internet-connected VoIP Session Initiation Protocol (SIP)-based...
