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

Chapter 161
Methods of Deploying IPv6

IPv6 will not be cut over in an hour’s time. A period of transition will take place. In order to effect the transition some suggested methods are provided:

Dual IP layer. IPv4 and IPv6 running at the network layer in both hosts and/or routers. These nodes have the ability to send and receive both IPv4 and IPv6 datagrams. This requires that a node be configured with both an IPv4 and IPv6 address that may or may not be related. In this way, IPv4-only hosts can access services that exist on an IPv6 host.

IPv6 over IPv4 tunneling. This is the process of taking an IPv6 datagram and wrapping an IPv4 header on it for transit across IPv4 hosts or routers. Two methods are available: configured and automatic. These nodes are configured with an IPv4-compatible IPv6 address. This is that special unicast address that has a 96-bit prefix of all 0s. The next 32 bits is an IPv4 address.

Configured tunneling is when the IPv4 tunnel endpoint address is determined by the encapsulating node.

Automatic tunneling is when the IPv4 tunnel endpoint is determined from the IPv4 address of the IPv6 packet. A node may be capable of automatic and/or configured tunneling. Automatic tunneling uses the IPv4-compatible address scheme as shown in the slide. A node does not have to support dual stack IP to support tunneling.

The transition will also have special nodes:

IPv4-only node. A node that only understands IPv4.

IPv4/IPv6 node. A node that is running dual IP stacks and understands both IPv4 and IPv6.

IPv6-only node. A node that understands IPv6 only.