Illustrated TCP/IP by Matthew G. Naugle Wiley Computer Publishing, John Wiley & Sons, Inc. ISBN: 0471196568   Pub Date: 11/01/98

Chapter 155
Unicast Addresses

The unicast address space is a contiguous bit-wise, maskable address that is similar to the addressing scheme used in IPv4 CIDR. The address types for unicast addressing are shown in the slide.

An expected to be very common type of address is where the IEEE 802.x (or Ethernet) LAN MAC addresses will be used as shown in the slide. The IEEE 802.x MAC address is 48 bits in length and because of its registry, every card has a unique number assigned to it. However, where these addresses are not available, E.164 (telephone) addresses could be used.

An interested point is that by using the IEEE 802.x MAC address, an IPv6 node could simply listen to the cable plant for router advertisements, which would yield the subnet ID for itself. Putting the two together would give it a unique address to use. This is autoconfiguration.

Refer to the slide. Global communication using IPv6 is provided by the unicast addressing scheme of a global-based provider. The first 3 bits identify the address as a provider-oriented unicast address. The registry ID identifies the internet address registry (currently IANA, RIPE, APNIC, and INTERNIC), which assigns provider identifiers, indicated by the provider ID field, to internet service providers, which then assign portions of the address space to subscribers. This is a process similar to the address assignment policy used with CIDR and described in RFC 2050. The subscriber ID distinguishes among multiple subscribers attached to the internet service provider identified by the provider ID. This is like a customer number.

Unicast Addresses

The subnet ID identifies a specific physical link. There can be multiple subnets on the same physical link; however, a specific subnet cannot span multiple physical links. The interface ID identifies a single interface among the group of interfaces identified by the subnet prefix.