Overview

While it is possible to deploy (some) IPv6 systems as stand-alone islands, this approach does not support the ubiquitous end-to-end carrier-class VoIP services we have advocated in this text. To achieve this end-to-end connectivity significant portions of the IP infrastructure must be upgraded. This evolution starts with the introduction of interconnected mixed-technology networks.

As IPv6 is introduced in the IPv4-based Internet, a plethora of interworking issues will arise, including, but not limited to routing, addressing, and Domain Naming System (DNS). An important key to a successful IPv6 transition is compatibility with the large installed base of IPv4 hosts and routers. Customers at all levels will expect seamless interworking. The interworking issues apply to all types of IP-based networks, including VoIP networks; in particular, there may be a need at some point in the medium-term future to interworking 2G VoIP systems with newer 3G VoIP systems.

Because IPv6 and IPv4 will need to coexist on the intranet and in the Internet for some time to come, network applications, devices, and VoIP elements (proxies, phones, gatekeepers, and so forth) need to be able to communicate transparently with both IPv4 and IPv6 nodes. It follows that there is a need for IPv4 compatibility mechanisms that can be implemented by IPv6 hosts and routers. Such mechanisms, as specified in RFC 2893, include providing complete implementations of both versions of the Internet Protocol (IPv4 and IPv6) (aka dual-stack deployment), and tunneling IPv6 packets over IPv4 routing infrastructures. These mechanisms are designed to allow IPv6...