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

Chapter 140
IPv6 Features

Widespread implementation of IPv6 will be phased in for the next couple of years. IPv6 is up and running today, however, through a series of islands that run autonomously and also use part of the current IPv4 Internet. It is known as the 6Bone and complete information can be found at:

www.6bone.net.

IPv6 can be grouped into the following categories:

Expanded addressing capabilities. IPv6 increases the IP address size from 32 bits to 128 bits to support more levels of addressing hierarchy, a much greater number of addressable nodes, and simpler autoconfiguration of addresses. There are three types of addresses: unicast, anycast, and multicast. The scalability of multicast routing is improved by adding a “scope” field to multicast addresses. There is no broadcast address defined.

Header format simplification. To make IPv6 more efficient, some of the header fields have been dropped and the header is a static 40 bytes.

Improved support for extensions and options. Since the IP header is a static 40 bytes and changes in the header cannot be made, the concept of header extensions is in. This provides greater flexibility for introducing new options in the future.

Flow labeling capability. A new capability is added to enable the labeling of packets belonging to particular traffic “flows” for which the sender requests special handling, such as nondefault quality of service or “real-time” service.

Authentication and privacy capabilities. Added support for authentication, data integrity, and optional data confidentiality through the extensions.

IPv6 routing uses the concept of prefix routing. Every address has an associated prefix which is simply a mask identifier to indicate how many of the bits, starting from the left are used for routing and how many bits are used to identify a host. The routers will use the prefix in order to build routing tables. End stations make the prefix similar to today’s subnet mask.

The existing routing protocols can employ IPv6 addresses as well. There is no need to specifically upgrade your network to employ Interdomain Routing Protocol to use IPv6. The existing routing protocols mostly have to change to understand 128-bit addressing.